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SSCHSC43168 P0025971

Senior ScienceHSC CourseStage 6

Lifestyle chemistry

Incorporating October 2002

AMENDMENTS

Number: 43168 Title: Lifestyle chemistry

All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith.

This publication is copyright New South Wales Department of Education and Training (DET), however it may contain material from other sources which is not owned by DET. We would like to acknowledge the following people and organisations whose material has been used: Cross section of human skin under a microscope, courtesy of Selby-Biolab Part 3 p 21

Published by Centre for Learning Innovation (CLI) 51 Wentworth Rd Strathfield NSW 2135 _______________________________________________________________________________________________

_ Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of the Centre for Learning Innovation (CLI). © State of New South Wales, Department of Education and Training 2008.

Introduction i

Contents

Module overview ........................................................................ ii

Resources............................................................................................ iii

Icons .....................................................................................................v

Glossary............................................................................................... vi

Part 1: The substances you use..........................................1–39

Part 2: Mixing it up...............................................................1–38

Part 3: Your skin..................................................................1–33

Part 4: What’s growing on your skin? ..................................1–29

Part 5: Dissolve it! ...............................................................1–36

Part 6: Good medicine.........................................................1–40

Student evaluation of module

ii Lifestyle Chemistry

Module overview

Welcome to the Lifestyle chemistry module for the HSC component ofthe Senior Science course.

If you have ever wondered why some soaps, detergents of cleansers workbetter than others then this module will help answer your queries.

You will first study the common substances you use and identify them assolutions, suspensions or colloids. You might be surprised to find thatmany of the substances you use daily are a type of colloid. You will beinvolved in the kitchen preparing some tasty foods that are classified assuspensions and colloids.

This module will enable you to more easily understand the chemistrybehind your soaps and detergents based on their ingredients. As youlearn about the properties of water and alcohol as solvents, you willinspect the labels of common substances in the home for their ingredientsand the solvents used in them. You will even better understand thechemistry behind substances that feel warm or cool on your skin.

Despite the use of soaps and detergents you have microbes that live onyour skin. You will understand their role and natural skin acidity inprotecting you against disease through an audiotape or internet audiofiles from the www.lmpc.edu.au web site. You will test the pH of arange of skin and hair products.

You will be asked to test the manufacturer’s claims of a skin or hairproduct. You might choose to test different shampoos for claims ofimproved body or shine. This experiment will take the form of anopen-ended investigation.

Lastly, you will appreciate different forms of medication such ascapsules, enteric coated and slow release tablets and implants placedunder the skin and relate these to the solubility of the drugs involved.

Enjoy Lifestyle chemistry. Be aware you may find yourself explaining topeople why substances and medications work.

Introduction iii

Resources

You will need the following equipment to carry out activities andexperiments during the module. In most cases, you should have most ofthe items listed around your home. If not, some items can be madeeasily, with little expense.

Part 1

• scissors

• glue

• sugar

• coffee

• salt

• milk

• ingredients and equipment to make:

– meringues

– salad dressing

– mayonnaise

• flour

• soil

• teaspoon

• two glasses or transparent cups

• funnel

• pen-sized laser pointer OR a torch with scissors, cardboard andrubber band

• filter paper / paper towel / coffee filters from a supermarket

• cook books

• common substances found in the home

iv Lifestyle Chemistry

Part 2

• pin or paper clip

• three waxy leaves

• toothpicks

• a packet of jelly snakes

• a packet of jelly beans or another type of jelly lolly

• detergent

• oil

• small jar

Part 3

• Skin audiotape and tape player or access to www.lmpc.edu.au Skinaudio files

• shampoo label

• soap label

• cleanser label

• light microscope (optional)

• prepared slide of a skin cross section (optional)

Part 4

• 20 cm length of universal pH paper (supplied by teacher)

• coloured pencils

• eight skin and/or hair products

• eight cotton buds or ice cream sticks

Part 5

• six cosmetics and/or medications for external use from home

Part 6

• vitamin pills label

• a variety of drug forms – capsules, tablets, enteric coated tablets,slow-release tablets

• transparent containers

Introduction v

Icons

The following icons are used within this module. The meaning of each iswritten beside it:

The hand icon means there is an activity for you to do.It may be an experiment or you may make something.

The talk icon guides you to discuss a topic with others.

There are exercises at the end of each part for you tocomplete and send to your teacher.

The headphone icon asks you to complete an activitywhile listening to an audio file.

The safety glass icon points out that care needs to be takenwhen carrying out a task.

There are suggested answers for the following questions atthe end of each part.

vi Lifestyle Chemistry

Glossary

The following glossary provides the scientific meaning for many of theterm used in this module, Lifestyle chemistry.

The HSC examiner will expect you to understand the meaning of everyscientific term used. If you find a term that you do not understand, thenlook it up in a scientific dictionary or ask your teacher for assistance.

acid substance capable of forming hydrogen ions whendissolved in water; substance with a pH below 7

acid mantle the slightly acid pH of skin, protecting the bodyagainst colonisation by disease-causing organisms

adhesive forces forces acting between molecules of a substance andmolecules of another substance

alkali substance which produces an alkaline solution(containing hydroxide ions) with a pH greater than 7

amino acid basic unit of protein; a protein is made up ofhundreds or even thousands of amino acid units

apocrine gland releases sweat which helps with cooling byevaporation; found alongside coarse hair

bacilli rod shaped bacteria

bacteria single celled procaryotic organisms belonging to theprotist kingdom

beading becoming sphere-shaped

biodegradable a substance capable of being broken down by theaction of living organisms

capsule cylinder shape with rounded ends, usually made ofgelatin and in two parts that can be opened

cocci sphere-shaped bacteria; coccus is one bacterium

cohesive forces forces acting between molecules of the samesubstance eg. hydrogen bonds between watermolecules

colloid mixtures where large molecules or small clusters ofmolecules are dispersed through the liquid and do notsettle out

Introduction vii

dermal patch thin medicated strip applied to the skin; deliversmedication to the body through the dermis eg.nicotine patch

dermis innermost layer of skin containing sweat glands, heatsensors, thermoregulators and blood vessels

disperse to spread out

dissolution dissolving

dissolving a solute mixing with a solvent, forming a solution

emulsifier emulsifying agent eg. soaps, gums, sulfonates,quaternary ammonia compounds

emulsifying agent material which makes it possible to stabilise a colloidor emulsion

emulsion dispersion of a liquid in another liquid in which it isimmiscible

enteric coated coated with a stomach acid resistant layer thatdissolves in the alkaline small intestine

enzyme protein which is a catalyst for a biochemical reactionsuch as protein synthesis or hydrolysis of fat

epidermis outermost layer of skin; protects the underlyingtissue, forms a barrier from heat loss, water loss andmicro-organisms

ethanol CH3CH2OH colourless liquid alcohol, miscible withwater; produced by yeast fermentation of a sugar

fibroblast cell which maintains skin elasticity

gall bladder stores bile to aid the digestion of fats

hair traps heat on the surface of the skin; insulation layer

hair bulb site of hair growth

hair follicle the under skin section of hair

helical spiral shaped

hydrophobic water repelling

hydrophilic attracted to water

hydroxide group hydrogen atom and oxygen atom joined togetheroften as a negatively charged ion OH-

immiscible incapable of mixing to form a solution

keratin tough protein present in the epidermis of vertebrateorganisms; in hair, feathers, fingernails

viii Lifestyle Chemistry

large intestine part of the alimentary canal (digestive system);absorbs water from wastes to produce faeces

liver produces and sends bile to the gall bladder to aid thedigestion of fat

lymph liquid, mostly water from blood, drained from thespaces between cells back to the circulatory systemnear the heart

melanin pigment present in skin and hair; its presence orabsence determines colouring of skin and hair

melanocyte produces and injects melanin into surrounding cellsfor skin pigmentation

meniscus the surface shape of a liquid; dependant on cohesiveforces between molecules and the adhesive forcesbetween molecules and the container.

methanol CH3OH colourless liquid alcohol; miscible withwater;

microbes microscopic single celled organisms

micro-organisms microscopic single celled organisms

mite very small arthropod; some are free living; some areparasitic

mixture two or more substances not chemically combined

mould fungal growth

muscle tissue involved in movement; causes hair to becomeerect, trapping warm air close to the surface of theskin, helping temperature regulation

narcosis general anesthesia

narcotic drug producing narcosis

non-polar molecule with no electric charge; non-ionic

oesophagus tube connecting the mouth to the stomach

pancreas produces enzymes which aid digestion of proteins,lipids and carbohydrates

pathogen disease-causing organisms

pH hydrogen ion concentration; pH = - log [H+];pH scale commonly ranges from 0 to 14; measure ofacidity and alkalinity

polar a molecule containing an electric charge; ionic

Introduction ix

polymer a large molecule made of a chain of monomers withthe same chemical structure

rectum stores and passes intestinal waste to the exteriorthrough the anus

sebaceous gland produces oils to lubricate the hair and skin

sebum oil produced by sebaceous glands in the dermis

secondary hair darker, wiry hairs emerging after puberty from vellushair follicles

slow-release designed to provide slow release over time

small intestine site of digestion and absorption of the products ofdigestion

soluble capable of dissolving

solution contains dissolved substances that are uniformthroughout, is transparent and may be coloured; thesolute is dissolved entirely in the solvent

solvent the substance in which a solute dissolves

staphylococci cocci bacteria appearing in grape-like formations

stomach site of protein digestion; contains strong acid ingastric juices

subcutaneous layer consists of larger connecting veins and arteries andfatty tissue to help insulate the body

subdermal implant inserted under the skin to release medication over aperiod of time

surfactant surface active agent with one end of each moleculecapable of dissolving in water and the other capableof dissolving in oil; substance that lowers the surfacetension of a liquid

suspension insoluble solids suspended in liquids; the solidseventually settle upon standing

sweat gland excretes saline water; releases body heat throughevaporation of sweat (cooling)

synthetic artificial as opposed to natural; made in a laboratoryor chemical factory

vellus hair fine, short, fair hair covering the body

yeast single celled fungus; used in brewing and baking

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Senior ScienceHSC courseStage 6

Lifestyle chemistry

Part 1: The substances you use


AMENDMENTS

Senior Science Stage 6 HSC Course

Lifestyle Chemistry

• The substances you use

• Mixing it up

• Your skin

• What’s growing on your skin?

• Dissolve it!

• Good medicine

Medical Technology – Bionics

Information Systems

Option

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Part 1: The substances you use 1

Contents

Introduction ............................................................................... 2

Common substances................................................................. 4

Substance use in retail.........................................................................5

Properties of substances .....................................................................6

Mixtures..................................................................................... 8

Solutions, suspensions and colloids....................................................9

Colloid types............................................................................ 16

Colloid classification...........................................................................19

Making colloids and suspensions......................................................21

Summary................................................................................. 23

Appendix 1 .............................................................................. 25

Appendix 2 .............................................................................. 27

Suggested answers................................................................. 29

Exercises – Part 1 ................................................................... 33

2 Lifestyle chemistry

Introduction

At the end of Part 1 you should be able to: classify some commonsubstances as solutions, suspensions or colloids; make some suspensions,solutions and colloids and appreciate the wide range of chemicals weregularly use from food to paint. Be aware that Part 1 should take aroundsix hours to complete.

In Part 1, you will be given opportunities to learn to:

• identify that a wide range of substances are used daily as part of ourfood, our hygiene, our entertainment and maintenance of our health

• identify that solutions, colloids and suspensions occur in a widerange of consumer products

• explain that mixtures can be

– solutions that contain dissolved substances and are uniformthroughout

– suspensions containing particles that settle out, or form layers,quickly

– colloids with particles that remain suspended for long periods oftime and include

– liquid-in-liquid (emulsions)

– oil-in-water

– water-in-oil

– gas-in-liquid (foams)

In Part 1, you will be given opportunities to:

• process and analyse information to identify the range of chemicalsused in every day living including:

– detergent

– lubricant

– pesticide

– solvent

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– metal cleaner

– body hygiene chemicals

– cosmetic

and outline any precautions that may be needed in the use andhandling of these chemicals

• use first-hand or secondary sources to gather, process, analyse andpresent information to identify examples of suspensions and colloidsand outline one advantage of a mixture being in each form

• plan, select appropriate equipment or resources for, and perform afirst-hand investigation to produce a range of suspensions andcolloids that are used by consumers including

– beaten or whisked eggs

– salad dressing (oil/ vinegar)

– mayonnaise

Extract from Senior Science Stage 6 Syllabus © Board of Studies NSW,October 2002. The most up-to-date version is to be found athttp://www.boardofstudies.nsw.edu.au/syllabus_hsc/index.html


Common substances

A substance is the material of which something consists.

What substances do you use every day? Have you ever wondered whatthese substances are made of? Why would you use some things for somesubstances and not others? Would you use soap as hair conditioner?Would you use dishwashing liquid to moisturise your skin? Would youuse window cleaner to wash the family car? Why not? Why aresubstances used for specific purposes?

1 List all the substances you use, every day from the time you wake up inthe morning until you go to bed at night. This includes the types of foodyou eat, hygiene, entertainment, cleaning and health needs. Don’t besurprised if you don’t have enough room for your answer!

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

Were you surprised with the amount of substances you use each day?

Think about other people and the substances they use each day. Theymay use: cosmetics; dental floss; hairspray; shaving cream; perfume orafter shave; vitamins; skin creams; laundry detergents; and cleaningproducts.

2 Can you think of any other substances other people use daily?

______________________________________________________

______________________________________________________

Businesses can use quite different substances on a daily basis than youuse. These substances are discussed in the following section.

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Substance use in retailThe following businesses use many different substances. Some of theseare listed below.

1 For each of the following businesses, add two more substances youassume the business uses regularly. If you are unsure, ask someone forhelp.

a) Hair salon

• hair dyes

• hair mousse

• perming solution

• ________________________

• ________________________

b) Cafe

• cooking oil

• disinfectant (for mopping floors)

• detergents (for washing dishes)

• ________________________

• ________________________

c) Service station

• engine oil

• water

• unleaded petrol

• ________________________

• ________________________

Check your answers.

2 Can you think of another retail industry and the substances it uses?Record your answer below.

• ________________________

• ________________________

• ________________________

• ________________________

• ________________________

Turn to Exercise 1.1 at the back of this part to identify a range of commonchemicals used in everyday living.


Properties of substances

A property is a characteristic or feature of something. Can you suggest aproperty of a chemical? Some properties of a chemical are: state ofmatter (solid, liquid, gas); colour; density; melting point; reaction withoxygen; reaction with acid and so on.

The properties of a chemical depend on:

• the particles that make up the chemical

• how the particles are arranged

• the forces (interactions) between the particles.

There are two main types of properties of chemicals – physical propertiesand chemical properties. A knowledge of these properties is important inidentifying the characteristics of a particular chemical.

Physical properties

A physical property is a property of the substance by itself. For example:

• state of matter

• colour

• density

• how it feels to touch

• odour

• taste.

Sometimes you rely on the physical properties of a substance for its use.You wouldn’t wear perfume or after shave unless it had the physicalproperty of odour. You eat certain foods for their taste. You chooseparticular paint for its physical colour properties.

Write down the physical properties of two other substances you use.

_________________________________________________________

_________________________________________________________

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Chemical properties

A chemical property is a property of the substance reacting with anotherchemical. Chemical properties are what we observe when a substancereacts with another chemical.

You have probably heard of elements, compounds and mixtures. Briefly,elements are made up of only one type of atom. Pure gold is an exampleof an element, containing only gold atoms. Compounds contain morethen one type of atom joined together. Water (H2O) is an example of acompound as it contains two hydrogen atoms and one oxygen atomjoined together. Mixtures contain different substances not chemicallycombined. Mixtures can often be separated by a process based on thephysical properties of the compounds.

This module focuses on mixtures. You use mixtures each time you washyour face, brush your teeth, drink soft drink, bake a cake, moisturise yourskin and the list goes on.

Sometimes you rely on the chemical properties of a substance to achievea desired outcome. Examples are:

• cake mixture changes from a liquid to a solid when baked

• some paint strippers react chemically with paint to remove it

• hair dye reacts chemically with hair and oxygen to colour the hair.

Chemical reactions are often very difficult to reverse. For example acake cannot be unbaked and the milk and flour separated.

Sometimes we rely on both the physical and chemical properties of asubstance. The hair dye example has important chemical properties,however the resultant physical property of colour is also important.

Can you think another example of a substance you use due to its chemicalproperties?

_________________________________________________________


Mixtures

Mixtures consist of more than one substance. Air is a mixture of gasessuch as oxygen, nitrogen, carbon dioxide and hydrogen. The substancesyou use will fall into three categories.

1 Use the code table below to determine the three types of mixtures.

a) solutions _______________

b) suspensions ________________

c) colloids _______________

a b c d e f g h i j k l m n o p q r s t u v w


2 Do you know what the above terms mean? Refer to the Glossary atthe beginning of this module to define each of the three types ofmixtures, from question 1.

a) __________________________________________________

__________________________________________________

b) __________________________________________________

__________________________________________________

c) __________________________________________________

__________________________________________________

Check your answers.

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Solutions, suspensions and colloids

You might be wondering what solutions, suspensions and colloids are.Their definitions are listed below.

Solution

Solutions contain dissolved substances that are uniformly spreadthroughout the solvent. A true solution is transparent and may becoloured. The solute is dissolved entirely in the solvent.

Suspension

Insoluble solids suspended in liquids are called suspensions.The solids eventually settle upon standing.

Colloid

Mixtures where large molecules or small clusters of molecules aredispersed through the liquid and do not settle out are colloids.

The particles in a colloid have the same electric charge on their surface.This common electric charge repels the particles from one another andkeeps them dispersed and moving throughout the liquid. The particlescannot join together to form a particle large enough to settle out. Finenegatively charged clay particles and charged protein on the surface ofbutter fat droplets in milk make fine clay in water and milk colloids. Theprotein and nucleic acid molecules floating in the fluid of living cells arecolloids.

The table on the following page outlines the characteristics of each typeof mixture at a glance. You will notice that the particle size; settling ofparticles to the bottom of the mixture; residue left after filtering; a lightbeam visible in the mixture when shone though the mixture; and theeffect of an electric current or an electric field are all measurablecharacteristics that define a mixture as a solution, suspension or colloid.


Characteristics Solution Suspension Colloid

particles smaller than 10-6 mm ✓ ✗ ✗

particles larger than 10-3 mm ✗ ✓ ✗

particles between 10-3 and 10-6 mm ✗ ✗ ✓

settling of particles ✗ ✓ ✗

residue left after filtering ✗ ✓ ✗

a light beam can be seen in the mixture ✗ ✓ ✓

affected by an electric current or field ✗ ✗ ✓

You should now be aware of the characteristics that define solutions,suspensions and colloids

From the table above, record all the characteristics of each mixture type.Some have been done for you as a guide.

a) Characteristics that define a solution are:

• particles smaller than 10-6 mm (0.000001 mm)

• no settling of particles

• __________________________________________________

• __________________________________________________

• __________________________________________________

__________________________________________________

b) Characteristics that define a suspension are:

• particles larger than 10-3 mm (0.001 mm) and can be seen undera light microscope

• __________________________________________________

• __________________________________________________

• __________________________________________________

• __________________________________________________

__________________________________________________

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c) Characteristics that define a colloid are:

• particles are between 10-3 mm and 10-6 mm (0.001 mm and0.00001 mm)

• _________________________________________________

• _________________________________________________

• _________________________________________________

• _________________________________________________

_________________________________________________

Check your answers.

You can use the characteristics that define solutions, suspensions andcolloids to determine which of the three categories some commonhousehold substances belong to.

Predict the categories each of the following mixtures, based on your currentknowledge. (The object of this exercise is to start you thinking about theproperties of different substance. This does not mean you have to be right.)

Mixture Solution/suspension/colloid

a) sugar in water mixture _______________________

b) salt in water mixture _______________________

c) milk in water mixture _______________________

d) coffee in hot water mixture _______________________

e) flour in water mixture _______________________

f) soil in water mixture _______________________

Are you ready to investigate which category those substances actuallybelong to? The activity on the following page investigates thecharacteristics of each substances above, helping you to identify eachmixture as a solution, suspension or colloid.


Substance classification

Aim

To investigate the properties of mixtures and use these properties to classify themixtures as solutions, suspensions or colloids.

Apparatus

You will need to collect:

• teaspoon

• sugar

• filter paper or paper towel orcoffee filters from supermarket

• salt • two glasses or transparent cups

• milk • funnel

• coffee

• flour

• soil

• pen-sized laser pointer (theseare class 1 or 2 lasers with apower output of < 1 milliwatt)OR a torch with scissors,cardboard and rubber band

Method (best at night in a room which can be darkened)

You can use the pen sized laser pointer as your light source butDON’T LOOK DIRECTLY AT THE LASER LIGHT BEAM.If a laser pointer is not available prepare a torch as shown in steps 1 to 5.

torch face

1 Place your torch face down on apiece of cardboard and tracearound the torch face.

2 Draw a second circle outside thefirst circle from step 1.

hole

cardboard 3 Cut around the larger circle.Place a hole in the centre using apen.

4 Cut inwards towards the centrecircle to create tabs.

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torch

rubber band

hole

beam of light

cardboard

5 Fold the tabs and place thecardboard over the torch face,securing it with a rubber band asshown. When the torch is on, abeam of light should comethrough the hole in thecardboard.

Record your observations in the table on page 12 as you work throughthe method:

6 Place a teaspoon of sugar in half a glass of water and stir twentytimes. This prepares a mixture of about 1% concentration.

7 Shine the beam of light through the sugar solution. Looking fromthe side can you see the light beam in the solution?

8 If you have round filter paper,fold it in half as shown in thediagram. If you are usingpaper towel, cut it into a circleshape with minimum diameterof 15 cm, then fold it in half.A coffee filter can be placedover the top of a glass or cup.

9 Fold the filter paper (or papertowel) in half again, then openout the paper to form a coneshape as shown. A coffeefilter is already made in acone shape.

10 Place the filter paper inside the funnel with a glass or cup underneathto catch the filtered solution. You may need to moisten the funnelwith water to keep the filter paper inside the funnel. You will need anew piece of filter paper or paper towel to filter each of the mixtures.

11 Filter the first substance by gently pouring the sugar mixture into thefilter paper, not allowing it to fill above the filter paper.

12 Leave the mixture to filter. Do any particles settle out? Is anyresidue left on the filter paper?

13 Make and test mixtures: salt with water; milk and water; coffee andwater; flour and water; and soil and water using the mixingdirections from Step 6.


14 Repeat steps 7-12 with salt mixture, milk mixture, coffee mixture,flour mixture and soil mixture.

15 Identify each type of mixture as a solution, suspension or colloid.

Results

Record your observations below.

Solute Light beam Filtering Settlingparticles

Solution orsuspensionor colloid?

sugar

salt

milk

coffee

flour

soil

1 Look at the characteristics that define a solution, suspension and colloid(on the previous pages). State which category each mixture belongs in.Explain your answer based on your results.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

2 Can you give other examples of common solutions, suspensions andcolloids? (Remember they must have all the characteristics of asolution, suspension or colloid)

a) solutions

__________________________________________________

b) suspensions

__________________________________________________

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c) colloids

_________________________________________________

Check your answers.

How do you think you could tell the difference between a solution,suspension and a colloid?

• Solutions appear clear, leave no residue when filtered and a lightbeam cannot be seen in the solution.

• Suspensions contain insoluble solids that will eventually settle,forming layers upon standing. Residue is left when filtered and abeam of light can be seen in the suspension.

• Colloids are mixtures of large molecules or small clusters ofmolecules dispersed in a liquid. Colloids are not clear, a beam oflight can be seen in the colloid, and no residue is left after filtering.

If the particles in these mixtures were magnified about one million timesthey could look like this:

edge of a roundsuspension particle

solution particles suspension particles colloid particles

The particles in a solution are much smaller than the wavelength of light.The particles in a suspension and colloid are larger than or similar in sizeto the wavelength of light and can scatter the light showing the beam.You are about to classify some common substances as solutions,suspensions and colloids. Use this information to help you classify.

Turn to Exercise 1.2 at the back of this part to classify some commonsubstances as solutions, suspensions or colloids.


Colloid types

You already know that colloids are mixtures where the particles between10–6 and 10–3 mm are dispersed in a liquid and don’t settle out. There areseveral types of colloids. The main colloid types you need to study are:

• solid-in-liquid such as water-based paint, ink, jelly, toothpaste

• gas-in-liquid foams such as mousse, whipped cream

• liquid-in-liquid emulsions such as oil-in-water or water-in-oil.

You may be surprised to find that some substances you commonly use fitinto one of these colloidal categories.

Often two different substances don’t mix well and require anemulsifying agent or emulsifier. The added emulsifying agent producesa stable dispersion of one liquid in another eg. soap added to oil andwater.

An emulsifier is a surfactant. It coats droplets of liquids eg. oil, causingthem not to stick to other oil molecules, therefore allowing them to bedispersed through a liquid it is not soluble in directly.

emulsifier

water

oiloil

Emulsifier stabilising droplets of oil in water

An emulsion is therefore a uniform mixture of two substances that arenormally immiscible. The term immiscible means unable to dissolve inanother substance eg. oil is immiscible in water.

Protein is often used as an emulsifying agent with food oils. Inmayonnaise the protein in egg coats food oil droplets, allowing the oil tobe dispersed through water.

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Detergents are emulsifying agents. They are attracted to the surfacesbetween oil and water. As soon as oil is broken up into droplets theemulsifying agent coats the droplets stopping them from joining together.This disperses the oil in water rather than leaving oil attached to platesand cups. The oil droplets do not join because of the emulsifier coating.

Think about oil and water. Oil usually floats on the surface of water.An oil-in-water colloid has small oil droplets dispersed through water.An emulsifying agent ensures the droplets are dispersed throughout thewater, at least for a short period of time depending on the properties ofthe emulsifying agent.

Gas-in-liquid

Can you think of any substances that are foamy? Many of them are usedin the bathroom. These are all gas-in-liquid colloids.

Examples of gas-in-liquid colloids are:

• soap suds

• hair mousse

• shaving foam

• beer foam

• soft drink foam

• whipped cream.

The foam that forms on the top of beer and soft drink consists of bubblesof carbon dioxide gas in liquid. As the bubbles burst the gas part is lostto the air and the liquid part joins the rest of the liquid.

Liquid-in-liquid

A mixture of two liquids where one is dispersed in the other is a liquid-in-liquid colloid or emulsion.

Examples of emulsions are:

• milk

• mayonnaise

• coffee and tea with milk

• cream.


Two very common types of liquid-in liquid colloids are:

1 Oil-in water colloids such as:

• water based salad dressings

• some water-based moisturisers

• sunscreen

• milk and cream

2 Water-in-oil colloids such as:

• oil-based moisturisers

• oil-based salad dressings

• butter

A way of distinguishing between oil-in-water and water-in-oil colloids

In an oil-in-water emulsion such as milk the oil droplets are dispersed inwater. If a drop of water soluble dye is added to an oil-in-water emulsionthe dye colour spreads and the emulsion appears the dye colour.

water soluble dye

water

oil

In a water-in-oil emulsion such as butter the water droplets are dispersedin oil (butter fat in the case of butter). Here the water soluble dye will notbe able to spread its colour throughout the emulsion.

water soluble dye

water

oil

.

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Other ways of distinguishing between the two main types of liquid-in-liquid use the temperature feel of skin and electrical conductivity.

Oil-in-water colloids like cold cream feel cold to the skin. Water has ahigh capacity for absorbing heat. Heat moves quickly from the skin intothe water and so the oil-in-water cream feels cold. By contrast water-in-oil colloids like ointments do not feel cold. The oil does not absorbmuch heat from the skin.

Oil-in-water colloids are better electrical conductors than water-in-oilcolloids

Colloid classification

Remember that all water-in-oil emulsions and all oil-in-water emulsionsare also liquid-in-liquid emulsions. For example, milk is a liquid-in-liquid emulsion and an oil-in-water emulsion. Butter is a water-in-oilemulsion and a liquid-in-liquid emulsion

1 Classify the following liquid-in-liquid emulsions as oil-in-wateremulsions or water-in-oil emulsions. To do this, you will have todetermine if the substance consists primarily of oil or water. If theemulsion is primarily oil it would be a water-in-oil emulsion.

a) milk

__________________________________________________

b) mayonnaise

__________________________________________________

c) coffee or tea with milk

__________________________________________________

2 Use the information on the previous pages to match the products in theAppendix 1 with the types of colloids below. Cut out the products in theAppendix 1 and stick them in the appropriate colloid column below.


Liquid-in-liquid colloid

Oil-in-water Water-in-oil

Gas-in-liquid colloid

Check your answers.

You will now create your own colloids and suspensions. This is not asdifficult as it sounds. You don’t need complicated scientific equipmentor chemicals. Almost every time you cook something in your kitchenwhere at least one ingredient is a liquid eg. milk, oil, melted butter,water, cream, juice, honey or vinegar, you make a colloid or suspension.

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Making colloids and suspensions

Are you ready to turn your kitchen into a laboratory? Are you a goodcook? You should enjoy eating your results!

Your aim is to produce a range of colloids and suspensions.Look up recipes for:

• meringues

• salad dressing with oil and vinegar

• mayonnaise

• smoothies.

Recipes for the foods listed are available in Appendix 2. If you are notsatisfied with these recipes, you may choose to use other recipes fromcook books at home or ask your family and friends for recipes.

Each of these recipes will demonstrate one form of colloid or suspension.You must:

• find and record recipes

• record the equipment and ingredients you will need

• make the mixtures from the recipes

• identify the type of colloid or suspension for each mixture.

One of the above recipes will settle out suspended solids if left standingfor a period of time, indicating it is a suspension. State which mixture isa suspension in your conclusion.

Turn to Exercise 1.3 to plan, carry out and report on your experiment.

Advantages

Why do you put sugar in your tea instead of consuming it separate to thetea? Why do you mix ingredients together, making a cake rather thaneating them separately? You answers are probably because they tastebetter. There are advantages to sugar dissolving in tea, forming asolution; and making a suspension such as a cake mixture.

What advantages do solutions, suspensions and colloids have?


List three advantages for each of the following solutions, suspensions andcolloids. It may help you to think about the different products that can bemade in each case eg. suspending sand and gravel in liquid cement helps thecement become firm when dry.

1 Dissolving sugar in water to form a solution.

______________________________________________________

______________________________________________________

______________________________________________________

2 Suspending solid particles in a liquid to form a suspension.

______________________________________________________

______________________________________________________

______________________________________________________

3 Mixtures of substances being even throughout by forming a colloid.

______________________________________________________

______________________________________________________

______________________________________________________

Check your answers.

Medicines in suspension form

Some medicines contain fine, undissolved particles suspended in a liquidbase e.g. calamine lotion. The particles settle to the bottom of thecontainers after prolonged standing. It is important to shake a suspensionwell before use to evenly distribute the drug particles.

Any medicine labeled suspension, lotion or emulsion should be checkedfor an instruction to shake well before use.

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Summary

1 Match the following substances with the category it belongs to bydrawing a line from the right column to the left column. You may useExercise 1.1 as a guide.

detergent moisturiser

lubricant Brasso®

pesticide dishwashing liquid

solvent engine oil

metal cleaner turps

body hygiene chemicals fungicide

cosmetics shampoo

2 You are now aware that substances you use regularly are solutions,colloids or suspensions. Refresh your memory by writing: solutions;colloids; or suspensions above each of the following definitions.

a) ________________________

Mixtures where particles between 10–6 and 10–3mm aredispersed through the liquid and do not settle out.

b) ________________________

Insoluble solids suspended in liquids. The solids settle uponstanding. Such substances require shaking before use.

c) ________________________

Mixtures containing dissolved substances that are uniformlyspaced throughout and appear clear. The solute is dissolvedentirely in the solvent.


3 a) What are three different types of mixtures?

__________________________________________________

b) What are the main types of colloids?

__________________________________________________

__________________________________________________

c) Name two common liquid-in-liquid colloids.

__________________________________________________

__________________________________________________

Check your answers.

Appendix 1

butter

mayonnaise

milk

skin moisturiser

hair styling mousse

French dressing

beer

sun protection cream



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Appendix 2

Meringue

Ingredients

11/2 cups of castor sugar 1 teaspoon cornflour

2 egg whites 1/2 a teaspoon of vanilla

1 teaspoon vinegar 4 tablespoons of water

Method

1 Preheat the oven at the lowest possible temperature (80–100°C).

2 Place all ingredients in a bowl and beat with an electric mixer untilshiny. This is as far as you need to go to do Exercise 1.3. To makethe cooked meringue continue with steps 3 and 4.

3 Desertspoonfuls of mixture may be placed onto a greased or linedtray or the mixture may be placed in a piping bag and piped onto agreased or lined baking tray.

4 Bake in a slow oven for one and a half hours or until dry and crisp.

Salad dressing

Ingredients

1/2 a cup of vinegar 1/2 a teaspoon of vanilla3/4 of a cup of vegetable oil 1/2 a teaspoon of mustard1/2 a teaspoon of salt pinch of black pepper1/2 a teaspoon of sugar 1 clove of garlic or half a

teaspoon of crushed garlic


Method

Blend all ingredients with a blender, food processor or hand mixer orplace all ingredients in a jar and shake.

Mayonnaise

Ingredients

11/2 teaspoons of mustard 1 cup of vinegar or lemon juice

400 g can of sweetenedcondensed milk

1 teaspoon of salt

1 egg

Method

Beat all together with a whisk, electric beaters or hand blender until wellmixed. It will thicken in the refrigerator.

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Suggested answers

Substance use in retail1 a) Hair salon: hair spray; hair gel, shampoo and conditioner are

some other substances.

b) Cafe: milk for coffee and tea; and breads, fruit and vegetablesare some other substances.

c) Service station: diesel fuel; and natural gas are some others.

Mixtures1 a) solutions

b) suspensions

c) colloids

2 a) Solutions contain dissolved substances that are uniformly spreadthroughout, are transparent and may be coloured.

b) Mixtures where insoluble solids are suspended in liquids aresuspensions. The solids eventually settle to the bottom uponstanding.

c) Colloids are mixtures of solute and solvent where largemolecules or small clusters of molecules are dispersed throughthe liquid and do not settle out.

Solutions, suspensions and colloids

a) Characteristics that define a solution are:

• particles smaller than 10-6 mm (0.000001 mm)

• no settling of particles

• an electric field has no effect on the solution

• no residue is left after passing through filter paper

• a light beam shone through a solution cannot be seen in thesolution.


b) Characteristics that define a suspension are:

• particles larger than 10-3 mm (0.001 mm)

• particles settle out on standing

• an electric field has no effect on the mixture

• residue is left after passing through filter paper

• a light beam can be seen when shone through the mixture.

c) Characteristics that define a colloid are:

• particles are between 10-3 mm and 10-6 mm (0.001 mm and0.00001 mm)

• particles do not settle out on standing

• an electric field will cause some particles to move to oneelectrode

• no residue is left after passing through filter paper

• the path of a light beam can be seen when shone through themixture.

Substance classification1 Sugar and salt in water are solutions because they are both clear,

transparent and leave no residue when filtered. Soil and flour inwater are both suspensions as a layer of solids settles out over aperiod of time. Milk in water and coffee in water are typicallycolloids as neither will settle out solids over time and no residue isleft after filtering (although this depends on the type of coffee youused; ground coffee will usually settle out a solid layer indicating itis a suspension).

2 a) Some common solutions are wine; spirits; and nail polishremover.

b) Some common suspensions are tea leaves in water; groundcoffee in water; liquid cake mix.

c) Some common colloids are milk; mayonnaise; egg white inwater; and cream.

Classifying colloids1 a) Milk is an oil-in-water colloid.

b) Mayonnaise is a water-in-oil colloid (the oil-based variety).

c) Coffee or tea with milk are both oil-in-water colloids.


2 Liquid-in-liquid colloid

Oil-in-water Water-in-oil

Gas-in-liquid colloid

French dressing

butter

hair styling mousse

sun protection cream

skin moisturizer

beer

milk

mayonnaise

Advantages 1 Dissolving sugar in water can make a drink sweeter, or into a toffee

or a syrup.

2 Advantages of suspending solid particles in a liquid are: small solids can be used in cosmetics as exfoliants; solid particles in liquids can provide the basis for coatings such as nail polish; and toothpaste contains fine solid particles as abrasives to remove plaque from teeth.

3 Advantages of mixtures that are even throughout are: oils used for cooking, vitamins and proteins are available to skin in moisturisers; oil droplets in milk help it taste better; and hair gel contains substances which help hair styling.


Summary

detergent dishwashing liquid

lubricant engine oil

pesticide fungicide

solvent turps

metal cleaner Brasso®

body hygiene chemicals shampoo

cosmetics moisturiser

2

a) Mixtures where particles between 10–6 and 10–3mm aredispersed through the liquid and do not settle out.

b) Suspensions are insoluble solids suspended in liquids. Thesolids settle upon standing. Such substances require shakingbefore use.

c) Solutions are mixtures containing dissolved substances that areuniformly spread throughout and appear clear. The solute isdissolved entirely in the solvent.

3 a) Three types of mixtures are solutions, suspensions and colloids

b) The main types of colloids are gas-in-liquid; liquid-in-liquid;solid-in-liquid.

c) Two colloid types that are liquid-in-liquid colloids are: oil-in-water and water-in-oil emulsions.

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Exercises - Part 1

Exercises 1.1 to 1.3 Name: _________________________________

Exercise 1.1

Are you ready to investigate the chemicals behind the substances youcommonly use?

Look for examples of the following substances in your home. If youcannot find all of these substances at home, are you able to visit a cousin,friend or neighbour? Perhaps a visit to your local supermarket might bequicker.

In this task you must observe the labels for ingredients and safetyprecautions for each of the eight substances listed in the table on thefollowing page.

You need to record:

• the trade name eg. Sunlight“ dishwashing liquid

• the number of different chemicals listed in the substance. (Count theingredients from the label)

• record the main ingredient (the first one on the ingredients list) or theactive ingredient(s)

• precautions required for handling the substance.

Some items may have only an active ingredient on the label, others mayhave no ingredients listed. Do your best to fill the entire table on thefollowing page, then answer the questions that follow.


Su

bst

ance

Examples Trade name Number ofchemicalslisted

Mainingredient

Activeingredient

Precautionsfor use

dete

rgen

t

dishwashingor laundrydetergent(withoutenzymes)

lubr

ican

t

Vaseline orengine oil

pest

icid

e

fungicides

solv

ent

nail polishremover orturps

met

alcl

eane

r

Brasso® orsilver cleaner

body

hyg

iene

chem

ical

s

shampoo,soap ordeodorants

cosm

etic

s

moisturiser,foundation, orlipstick

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1 What substances appear to contain the greatest number ofingredients?

_____________________________________________________

_____________________________________________________

2 Which substances have detailed precautions for use?

_____________________________________________________

_____________________________________________________

3 Choose two substances with safety precautions listed on the label.What effect could these substances have if the precautions were notfollowed?

_____________________________________________________

_____________________________________________________

_____________________________________________________

Exercise 1.2

Are you ready to classify some common substances as solutions,suspensions or colloids? You may refer to the information on pages 9 to15 to help you determine which classification each substance belongs in.

You are to:

• find, observe and classify six of the following substances: soft drink;shaving foam; nail polish remover; nail polish; turps, deodorant orantiperspirant; after shave or perfume; paint; moisturiser; and hairconditioner

• observe and classify two other items at home as solutions,suspensions and colloids.

If you cannot find these substances at home, can you visit a supermarket,cousin, friend or neighbour?

An example is provided on the following page as a guide.


Substance andtrade name

Observations Solution,suspension orcolloid

orange juice

Today’s Fresh®

• not clear

• can see a beam of light in substance

• particles have settled to the bottom,forming a layer

suspension

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Exercise 1.3

Normally you do not taste chemicals or mixtures of chemicals. Howeverwhen you use Appendix 2 you make colloids and suspensions that youcan taste. Plan and carry out your tasty experiments on making colloidsand suspensions.

Aim

State what are you trying to do.

_________________________________________________________

_________________________________________________________

Apparatus

Record the equipment and ingredients you will require while making thethree recipes below. Appendix 2 contains recipes for each. If you use analternative recipe indicate the different ingredients and equipment.

Rec

ipe Ingredients Equipment required

mer

ingu

em

ayon

nais

esa

lad

dres

sing


Method

Record, or stick in copies of each recipe. If your recipes are larger thanthe spaces provided, you may copy them onto sheets of paper, fold themand stick them in the spaces below.

Meringue

Mayonnaise

Salad dressing

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Results

Classify each mixture prepared as a:

• suspension or

• colloid:

– gas-in-liquid

– liquid-in-liquid

– solid-in-liquid

Recipe Suspension or colloid classification

meringue mix beforecooking

meringue mix aftercooking

mayonnaise

salad dressing

You may wish to take photos of your creations and attach them with thisexercise.

Conclusion

Use the criteria of colloids and suspensions to explain why each recipemixture is classified as you indicated above.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

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Lifestyle chemistry

Part 2: Mixing it up


AMENDMENTS


Lifestyle Chemistry


• Mixing it up

• Your skin


• Dissolve it!

• Good medicine


Information Systems

Option

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Part 2: Mixing it up 1

Contents

Introduction ............................................................................... 2

Surface tension ......................................................................... 4

Walking on water..................................................................................5

Water drops on leaves .........................................................................6

Why are water drops spheres?............................................................6

Optional activity ....................................................................................9

Water under gravity............................................................................11

Menisci................................................................................................11

Surfactants .............................................................................. 13

Use or surfactants ..............................................................................14

Emulsions................................................................................ 17

Emulsifiers ..........................................................................................19

Emulsion types ...................................................................................21

Biodegradability....................................................................... 22

Soaps and detergents........................................................................23

Summary................................................................................. 24

Appendix 1 .............................................................................. 25

Appendix 2 .............................................................................. 27


Exercises – Part 2 ................................................................... 33

2 Part 2 Lifestyle chemistry

Introduction

If you have ever wondered why water beads on polished cars; how someinsects walk on water; why detergents clean grease off plates; and what isreally meant by ‘biodegradable’, you will find out in Part 2. Don’t besurprised to find the reasons why substances you use, do what they do.

In Part 2, you will be given opportunities to learn to:

• explain surface tension in terms of the forces experienced byparticles at the surface of a liquid

• describe surfactants as substances that affect the surface tension of aliquid

• state the relationship between the properties of an emulsion and thetypes of molecules present

• outline the purpose of the emulsifying agent in a range of consumercleaning products

• identify that soaps and detergents are emulsifying agents andsurfactants

• explain why cleaning agents must be surfactants and emulsifiers

• define the term biodegradable

• discuss the biodegradability of soaps and soapless detergents


• perform first-hand investigations to demonstrate the effect of surfacetension and:

– the shape of liquid drops

– the formation of menisci

– the ability of some insects to walk on water

• process and present diagrammatic information to describe the effectsof soaps, skin cleansers and shampoos on the solubility of oil

• perform a first-hand investigation to prepare an emulsion andcompare its properties to those of a solution and suspension

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• plan, choose equipment or resources for, and perform a first-handinvestigation to gather information about the properties of differentemulsions and use available evidence to compare those properties



Surface tension

Water molecules are strongly attracted to each other. Water moleculeson the surface of water are strongly attracted to the surrounding surfacemolecules and the molecules beneath the surface. This strong attractioncauses the surface of the water to resist attempts to increase its surfacearea, thus allowing objects denser than water to sit on the surface. This isa physical property of water. Refer to the diagram below.

the water moleculesare strongly attractedto each other

force due to gravity

pin

Surface tension resists the gravitational force of the pin.

1 Gently place a metal pin or a paper clip on the surface of a glass ofwater. Try not to break the water surface with your fingers. Keeptrying until you float the pin or paper clip on the water surface.

If your pin or paper clip sinks, try again with another dry pin. Don’tuse pins with a pearl end as these tend to break the water surface andsink.

Use the above information to explain why a pin, which is clearly denser thanwater, is able to float on the surface of water.

_________________________________________________________

_________________________________________________________

_________________________________________________________

Check your answer.

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Walking on water

Water spiders rely on surface tension for mobility. They literally walkon water.

Do you live near a waterway, lake, dam or other still water body? If so, youare able to observe the ability of some insects to walk on water.

Aim

To observe the variety of organisms that can walk on water.

Method

Go to your nearest water body. Walk along the edge of the water body,observing the insects that walk on water. Walk slowly so as not todisturb the insects. Record the number of different species you observewalking on water over a fifteen minute period.

Results

Make a tally of the different species of insects walking on water.

_________________________________________________________

_________________________________________________________

Record the total number of species observed walking on water.

_________________________________________________________

_________________________________________________________

Conclusion

Fill in the blanks below. For example, ‘Six different species wereobserved walking on water in the Darling River water course.’

___________ different species were observed walking on water in the

_________________________ water body/course.


Water drops on leaves

Go outside and try to collect three waxy leaves.

Use whatever method you can to place a single drop of water on the waxysurface of each leaf – but be careful – the water may roll off. Draw whateach drop looks like on the leaf surface on the following page.

leaf 1 leaf 2 leaf 3

Cross sections of leaves

1 What was the general shape of the water on the leaves?

_____________________________________________________

2 Can you explain why the water formed that shape?

_____________________________________________________

_____________________________________________________

_____________________________________________________

Check your answers.

Why are water drops spheres?

Each molecule of water is attracted to the surrounding molecules fromabove, below and either side. On the surface of water, water moleculesare attracted only to the molecules on each side and underneath. Watermolecules on the surface are constantly being pulled towards the centre.For this reason water drops tend to form a sphere, reducing its surfacearea as much as possible.

A two dimensional analogy may help you understand the behaviour ofwater drops. Imagine a president with twenty security guards.

The security guards surround the president to protect him. Each securityguard tries to stay close to other security guards. This represents theforces of attraction between water molecules. The security guards don’twant to expose the president to an assassin. For this reason they will try

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to reduce the surface area exposed to assassins as much as possible,making a circle around the president. Water drops reduce their surfacearea as much as possible, simply because the forces between the watermolecules in the drop of water are so strong – just like the forces betweenthe security guards and the president.

Modelling a water drop

You are about to make a model showing the internal forces of a water drop.For this activity you will need:

• toothpicks

• jelly snakes

• jelly lollies such as jellybeans or jelly babies

1 Break seven toothpicks into three even pieces. Each piece should beabout 2 cm long.

2 Cut four snakes into three pieces each. Each piece should be about4-5 cm long.

3 Collect six jelly lollies. (For the rest of this experiment, jelly lollieswill be referred to as jellybeans because jellybeans were used for theillustrations. If you chose jelly babies, wild raspberries or anothertype of jelly lolly, these replace jellybeans throughout theexperiment.)

4 Stick three toothpick pieces into a jelly bean. Each toothpick pieceshould be half sunk into the jelly bean and half sticking out. Refer tothe diagram below which represents steps 4, 5 and 6.

5 Stick a piece of snake end-on onto the toothpicks attached to eachjelly lolly. Refer to the diagram below, which also includes step 6.

6 Stick three more toothpickpieces on each end of thesnake pieces as shown. Half ofeach toothpick piece should beshowing.

A jellybean represents a water molecule (H2O). The snakesrepresent the cohesive forces between water molecules. These arethe forces attracting water molecules to other water molecules. Thetoothpicks only serve to join the jellybeans and snakes and are tobe ignored in the model.


7 Continue steps 4,5 and 6 untilyour model resembles thediagram opposite.

The jellybeans in a row on the previous page represent the watermolecules at the surface of water. The snakes represent the forcesbetween water molecules on the water surface. The snakespointing down represent the cohesive forces between watermolecules on the surface and those beneath the surface.

8 Join the two ends of the chain,forming a circle. Attach thefive inside snakes to a jellybean in the centre as shown inthe diagram opposite.

Forces act between surface molecules and water molecules belowthe surface. When there are fewer water molecules beneath thesurface, the surface molecules stick to those fewer molecules,causing the water surface to become circular. Your modeldemonstrates this with only one water molecule in the centre.In reality, there are thousands of water molecules inside a waterdrop, each with the cohesive forces described. In three dimensions,these cohesive forces cause a small amount of water to becomespherical in shape.

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Explain how your model demonstrates why a water drop is spherical.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

Check your answer.

Water drops are three dimensional. Do you want make your model threedimensional? If so, take the challenge by doing the following optionalactivity – but don’t dismantle your model – you will need it for thefollowing activity. If not, enjoy your model, but save some snakes,toothpicks and jellybeans for an experiment later in this part.

Optional activity1 Stick five toothpick pieces into

the centre jelly bean and twotoothpick pieces into theoutside jellybeans each, asshown in the diagram opposite.

2 Attach a piece of snake to eachof the toothpick pieces fromabove.

3 Attach another toothpick pieceto the end of each snake asshown.

4 Join all the snakes withjellybeans as shown in thediagram opposite. (This maybe fiddly – but you can do it!)


5 Stick a single toothpick pieceinto the five jellybeans from theprevious step. See thediagram opposite.

6 Attach a piece of snake to eachof the toothpick pieces fromstep five. Then attach all fivepieces of snake to a single jellybean on top. Your modelshould look like the oneopposite.

7 Lastly, attach the top jelly beanwith the one in the center at thebottom. This is shown in thediagram opposite.

Congratulations! You just made a three dimensional model showing thecohesive forces between water molecules. Your model should resemblehalf a sphere. If you carried out the same steps on the other side of themodel, it would become a complete sphere. This would resemble a waterdrop.

List any problems you had while constructing the three dimensionalmodel.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

Don’t forget to save some snakes, jellybeans and toothpicks for later inthis part.

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Water under gravity

You may be wondering why a water drop from a tap is shaped like a teardrop instead of a sphere. The answer is gravity.

The force of gravity causes the majority of water molecules toaccumulate towards the bottom of the drop, leaving fewer molecules atthe top. This causes the tear shape.

1 The diagram below shows a spherical water drop. Sketch over the topof the drop to show the effect of gravity on the drop of water.

Spherical water drop.

2 Explain in your own words why falling water drops appear tearshaped.

_____________________________________________________

_____________________________________________________

_____________________________________________________

Check your answers.

Other liquids such as oils, liquid mercury, alcohol and many more havedifferent forces acting between molecules. These forces determine theirsurface shape.

Menisci

Have you ever noticed that the surface of water in a glass? The watersurface curves up at the edges. This curved surface is the meniscus(plural: menisci). The water molecules are attracted to the glass throughadhesive forces. Cohesive forces between water molecules cause themto ‘stick’ together.


The water prefers to ‘stick’ to the glass surface, however these watermolecules still attract other water molecules. The water molecules try toadhere to more of the glass surface, thus moving up the side of the glass.Other water molecules are attracted to these molecules and move withthem. Gravitational forces will only allow the water to move a shortdistance. The result is the meniscus you see in a glass of water.

The diagram below shows a meniscus of water.

water

meniscus

beaker

Meniscus of water.

Turn to Exercise 2.1 at the back of this part to observe menisci.

You may be wondering what all this has to do with Lifestyle chemistry.The forces acting on the surface of a liquid determine how it can be actedupon by surfactants.

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Surfactants

Surfactants are molecules that act at the surface of a liquid,lowering the liquid's surface tension.

Surfactants are shaped like tadpoles. The head is water soluble and thetail is oil soluble. There are four different types of surfactants:

• anionic (negatively charged head)

• cationic (positively charged head)

• non-ionic (no charge)

• amphoteric (positive and negative charges depending on the pH ofthe liquid).

Use the above information to identify each type of surfactant below.

Surfactant types.


Use of surfactants

Agricultural sprays

When you observed a drop of water on a waxy leaf, you should havenoticed the water beading or becoming a ball. If water is used as asolvent for agricultural sprays, the water is likely to bead and roll off theleaves with little effect on the plant.

Surfactants are added to the water to minimise its surface tension. Thesurfactant molecules get between the water molecules at the surface.This reduces the attraction between the water molecules so that instead ofhaving a strong outside layer able to form balls, the water spreads out.The water spreading over the surface of a waxy leaf coats it with the farmchemical. Refer to the diagram below.

leaf

Surfactants allowing chemical spray to spread over the surface of a waxy leaf.

Fire fighting

Silv-ex® foam is used to fight fires. The foam reduces the surfacetension of the water it’s mixed with. The foam sticks to the surface oftrees, grasses and other fire fuels, penetrating their surfaces and keepingthem wet, thus reducing the risk of ignition. It also prevents oxygenfrom reaching the fuel.

Cleaning

Detergents, soaps, cleansers shampoo and many other cleaning productsare surfactants. Their action is described in the following section.

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Froth floatation

Froth floatation is used in mining. The crushed rock is mixed with waterand aerated from below. The air bubbles rise through the mixture.The mineral particles are positively charged and readily stick to watermolecules.

When surfactants are added, the mineral particles stick to the negativesurfactants. The surfactant’s tails are more attracted to the air bubbles(rising through the solution) than to water, thus attaching to air bubblesand carrying the mineral particles to the surface. This separates themineral from its ore. See the diagram below.

air bublerising throughthe liquid negative

polar head

metal ionsenlargedview

froth

air pumped through pipes under pressure

Froth floatation of metal ions using air bubbles.


Imagine you are a teacher. Your students must learn about the use ofsurfactants. Your students have the information on pages 13 and 14.

Write three questions about the use of surfactants. The questions must bedesigned in a way that helps the students understand what surfactants do andwhy they are used.

1 ______________________________________________________

______________________________________________________

2 ______________________________________________________

______________________________________________________

______________________________________________________

3 ______________________________________________________

______________________________________________________

______________________________________________________

Many surfactants are also used in the home as emulsifiers. The nextsection introduces you to the emulsifiers you use every day.

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Emulsions

You have already learnt about liquid-in-liquid colloids. All liquid-in-liquid colloids are also emulsions. You may be wondering what theexact definition of an emulsion is.

An emulsion is a mixture of tiny droplets of one liquid dispersed inanother in which it is immiscible.

Oil and water normally don’t mix, but oil may be emulsified to allow itto mix with the water.

Emulsification is the process of dispersing a liquid in another liquidin which it is immiscible as a stable colloidal dispersion.

Certain substances are used as emulsifiers to hold one substance inanother such as oil in water. Most, but not all, surfactants areemulsifiers.

An emulsifying agent is a substance added to a mixture to stabilisean emulsion.

The detergents you just learned about as surfactants are also emulsifiers.However, not all surfactants are good emulsifiers. You have dealt withsurfactants with very polar heads. This means the heads have a chargeon them. Non-ionic surfactants do not have very polar heads. Theseslightly polar surfactants do not emulsify well.


Oils do not dissolve in water well (they are immiscible). Emulsifiersstabilise oil broken up into smaller globules when the oil is shaken withwater. The emulsifiers then hold the oil globules in water, preventingthem from forming larger globules or floating to the surface.

After reading the boxed text on the previous page, you should understandthat emulsifiers disperse an immiscible substance and hold it in colloidalform – that is, dispersed in a liquid. If this seems too technical for you,the following paragraph using water and oil as an example may help.

Understanding emulsification

If you are finding it difficult to understand the action of emulsification,the following analogy may help.

Imagine a gang of criminals in a group as a large oil globule. Police arethe emulsifiers. They have the energy to hold one criminal each. A largenumber of police surround the gang, separating them into smaller groups.The police (surfactants) surround the smaller gangs, holding one criminaleach. The smaller gangs (oil globules) are unable to join back togetherdue to the force of the police (emulsifiers).

1 Can you think of another way to describe the action of emulsifiers?

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You should already know that cleaning agents contain surfactants.Liquids containing surfactants are more able to wet and cover the surfaceof immiscible liquids. Cleaning agents also need to be emulsifiers inorder to allow immiscible substances to be dispersed in colloid form.

2 Why must cleaning agents contain surfactants and emulsifiers?

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3 In a single paragraph, explain what emulsifiers do and their role informing emulsions.

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Check your answers.

Emulsifiers

Soaps, cleansers, shampoo and detergents are all emulsifiers. This meansthat they all act on the surface of grease and grime to remove it.

You may have observed oil floating on the surface of water. Oilmolecules are not attracted to water and are less dense than water,causing oil to float as oil slicks. So how do we get greasy dishes clean?What do you add to water when washing dishes, your hair, skin or face?You add emulsifiers. Detergents, soaps, cleansers and shampoos havemolecules with polar heads. This means that one end of each emulsifieris hydrophilic and attracted to water molecules; the other end ishydrophobic, repelling water, attracting it to oil molecules.

Emulsifiers work on dirty dishes in the ways described below.

1 Detergent is added to warm water. The hydrophilic ends of eachemulsifier are attracted to and dissolve in water.

2 The surface tension of the water is reduced, allowing water to spreadover the surface of the grease on a plate. The hydrophilic ends areattracted to the water molecules and the non-polar ends are attractedto oil.

3 The hydrophobic ends of emulsifiers dissolve in the oil, helpingdislodge it from the plate.

4 With some agitation, small globules of oil are lifted away from theoil on the plate.

5 Emulsifiers surround oil globules, keeping them dispersed,preventing them from joining up with other oil globules; as likeelectric charges repel each other. Some surfactants remain as a thinlayer on the plate surface to help repel oils.


Cut out the diagrams and stages in emulsifier use in Appendix 1.Stick them below in the correct order and with the correct diagram.

Role of emulsifier in detergent Diagram

Check your answers.

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Turn to Exercise 2.2 to model emulsification.

Turn to Exercise 2.3 to prepare an emulsion and compare its properties withsolutions and suspensions.

Cleaning agents

Cleaning agents must be both surfactants and emulsifiers.

Being surfactants they concentrate at surfaces orientating their polar endin the most polar liquid and their non-polar chain in non-polar liquid.

Being emulsifers, cleaning agents surround the liquid globules, keepingthem dispersed and stopping them from joining up with other globules.This enables the dispersed globules to be washed away.

Emulsion types

Emulsion types are the colloid types that involve only liquids, that is,they are liquid-in-liquid colloids. The two most common types of liquid-in-liquid colloid are oil-in-water and water-in-oil. If you just completedExercise 2.3, you made an oil-in-water emulsion.

In oil-in-water emulsions, emulsifiers act on the oil, dispersing oilthrough the water. In water-in-oil emulsions, the emulsifiers act on thewater, dispersing water through the oil.

How do you think you can tell the difference between a water-in-oil andoil-in-water emulsion? This can be done by looking at the properties ofemulsions.

One way is to try to conduct electricity through each emulsion.Oil molecules have a greater electrical resistance than aqueous solutions.Water-in-oil emulsions conduct electricity poorly. Oil-in-wateremulsions conduct electricity much better than water-in-oil emulsions.

The subject of conductivity brings us to the second method of emulsionidentification. Just as water-in-oil emulsions resist conductingelectricity, so too do they resist heat conduction. For this reason water-in-oil emulsions feel relatively warm to touch. Oil-in-water emulsionsconduct heat quite well and feel cold to touch. Cold cream works on thisprincipal as it conducts heat away from your body where applied.


Biodegradability

Have you heard the term, biodegradable? The media andadvertisements often refer to biodegradability. What do you think ofwhen you hear the term biodegradable? Write your ideas below.

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So what does biodegradable really mean? Is the term as green asmarketing makes it appear to be?

Biodegradable means an organic substance capable of beingdecomposed by the action of naturally occurring organisms.

Almost all organic substances are biodegradable. However, somesubstances can take years to break down, while others take days.Biodegradable substances often break down in steps formingintermediates. Some of these intermediates can be harmful ordetrimental to living organisms eg. nonylphenol is suspected to mimichormones, disrupting normal hormonal processes in living things.

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Soaps and detergents

Read the information in Appendix 2 on soaps and detergents then answerthe questions following questions.

1 Draw a typical soap molecule below.

2 What substances can soap break down to form?

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3 Is soap biodegradable?

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4 Why was detergent produced?

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5 What were first detergents made from?

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6 Explain the problem associated with the first detergents.

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7 What problem was associated with second generation detergents andwhat was the solution?

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8 Do the detergents we use today contain phosphates? Explain why orwhy not.

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9 What detergents do we use today? Are they biodegradable?

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Turn to Exercise 2.4 at the back of this part to discuss the biodegradabilityof soaps and detergents.


Summary

Use the clues below to fill in the missing words. The highlighted columntells you what you will learn in Part 3.

1

2

3

4

5

6

7

8

9

10

11

12

13

1 surfactants are used in these toencourage leaf coverage (twowords; 12,6)

2 water repelling

3 water drops are this shape

4 an organic substance capable ofbeing decomposed by the action ofnaturally occurring organisms

5 made by the reaction of ahydroxide and fat

6 attracted to water

7 the resistance of a liquid’s surfaceto being broken (two words; 7,7)

8 surfactant with a negativelycharged head

9 molecule acting on the surface of aliquid, lowering its surface tension

10 incapable of being mixed to form ahomogenous solution

11 a common liquid-in-liquid emulsion

12 mixture of tiny droplets of liquiddispersed in another in which it isimmiscible

13 a synthetic surfactant andemulsifier used for cleaning

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Appendix 1

Emulsifiers surround oil globules,keeping them dispersed,preventing them from joining upwith other oil globules; as likeelectric charges repel each other.Some surfactants remain on theplate to help repel oils. plate

The surface tension of the wateris reduced, allowing water tospread over the surface of thegrease on a plate. Thehydrophilic ends are attracted tothe water molecules and the non-polar ends are attracted to oil. plate

With some agitation, smallglobules of oil are lifted awayfrom the oil on the plate.

plate

grease

Detergent is added to warmwater. The hydrophilic ends ofeach emulsifier are attracted toand dissolve in water.

plate

The hydrophobic ends ofemulsifiers dissolve in the oil,helping dislodge it from the plate.

plate

grease


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Appendix 2

Soaps and detergents

The following information has been sourced from:Laidler, G. 1991. Environmental Chemistry – an Australian Perspective –Second Edition. Pearson Education Australia.

Soap has been used as a cleaning agent for over 4500 years. A typicalsoap would be sodium stearate C17H35COONa (carbon, hydrogen,oxygen and sodium), shown in the diagram below.

C

H

H

CO–Na+

OC

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HH

C

H

H

Sodium stearate © Laidler, G. 1991 Environmental Chemistry An AustralianPerspective – Second Edition Pearson Education Australia.

The part of the soap with the long carbon chain is water repelling orhydrophobic. The charged end of the soap is hydrophilic and attractswater. The soap works because the carbon chain end of the moleculedissolves in the grease or dirt, and the ionic end dissolves in the water.Soap does not function as a cleaning agent in acidic environments.

Soap is made from renewable natural resource and is biodegradable, thismeans it can be broken down into simple molecules (CO2, H2O) bybacteria in the environment.

Detergents were introduced in the 1950s with better cleaning action thansoap. Their synthetic make up differed from soap, which is made fromthe action of a hydroxide on a natural fat.

These branched alkyl benzene sulfonate detergents were too slowlybiodegradable, accumulating in lakes, rivers and sewage treatmentworks. Such detergents were responsible for frothing and bubbling inwater ways in the 1960s and early 1970s. An example of these detergentmolecules is shown on the following page.


CH3

CH3 CH CH2 CH CH2 CH CH2 CH S O–Na+

O

O

CH3CH3CH3

represents a benzene ring CC

C

C

CCH H

H

H

H

H

Branched alkyl benzene sulfonate (ABS) © Laidler, G. 1991 EnvironmentalChemistry An Australian Perspective – Second Edition Pearson EducationAustralia.

New (second generation) detergents were formulated. The straight chaincarbon molecules were more readily biodegradable. An example isshown below.

CH3 CH2

CH3

CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH S O–Na+

O

O

Straight chain alkyl benzene sulfonate (ABS) detergent © Laidler, G. 1991Environmental Chemistry An Australian Perspective – Second Edition PearsonEducation Australia

These detergents were expensive and phosphates were added to reducethe expense. The phosphates could hold calcium, magnesium and ironions in suspension, preventing a scum from forming.

Disposal of phosphate detergents added a great deal of phosphate towater courses, causing algal blooms and eutrophication. Thirdgeneration detergents now contain straight chain ABS detergents as theactive ingredient. The bulk is added in the form of sodium carbonate,sodium perborate, sodium sulfate or sodium metasilicate. They arebiodegradable, taking slightly longer than soap to degrade.

In domestic detergents, the surfactant molecules carry a negative chargeand are called ionic surfactants eg. alkyl benzene sulfonate. Surfactantmolecules can also be made with a positive charge. These surfactants aremore expensive, but are antibacterial, soften fabric and are therefore usedin nappy rinses and shampoos. Shampoos can also contain non-ionic andamphoteric surfactants.

Soaps and detergents are emulsifying agents because they stabilisemixtures of two immiscible substances, such as oil and water, after thetwo liquids have been shaken together. Soaps and detergents are alsosurfactants (surface active agents) because they have a hydrophilic partand a hydrophobic part; this causes them to concentrate at surfaces suchas between water and air or between water and oil.

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Suggested answers

Surface tension

The forces of attraction between the water molecules on the watersurface cause surface area to be minimised. The surface resists anyattempts to increase its surface area, thereby allowing the pin to floatrather than break the water surface.

Water drops on leaves1 Water drops are a spherical shape on a leaf’s surface.

2 The water molecules cling together, resisting the waxy leaf.The outermost water molecules are pulled towards the centre,therefore reducing the surface area of the water drop, causing aspherical shape.

Modeling a water drop

The model shows the forces between the surface water molecules and thewater molecules beneath the surface. When less water molecules arebelow the surface, the forces between the surface molecules and thoseunder the surface cause the surface to become spherical. (Other answersare acceptable.)

Water under gravity

1

2 Falling water drops appear tear shaped because gravity causes mostof the water molecules to condense towards the bottom of the drop,leaving fewer molecules at the top. (Other answers are acceptable.)


Surfactants1

anionic

cationic

nonionic

amphoteric

Emulsifiers

Role of surfactant in detergent Diagram

Detergent is added to warm water.The hydrophilic ends of each emulsifierare attracted to and dissolve in water.

plate

grease

The surface tension of the water isreduced, allowing water to spread overthe surface of the grease on a plate.The hydrophilic ends are attracted tothe water molecules and the non-polarends are attracted to oil. plate

grease

The hydrophobic ends of emulsifiersdissolve in the oil, helping dislodge itfrom the plate.

plate

With some agitation, small globules ofoil are lifted away from the oil on theplate.

plate

Emulsifiers surround oil globules,keeping them dispersed, preventingthem from joining up with other oilglobules; as like electric charges repeleach other. Some surfactants remainon the plate to help repel oils. plate

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Understanding emulsification1 An example analogy is: a group of star wars fighter craft represent

oil. They are attacked and broken up by enemy fighters. The enemyfighters represent emulsifiers. The enemy surround small groups ofstar wars fighters, preventing them from forming a group. The starwars fighter crafts are effectively emulsified.

2 Cleaning agents must be surfactants to wet surfaces for dirt andgrease removal. They must also be emulsifiers to keep dirt andgrease from re-accumulating and re-coating surfaces.

3 Emulsifiers for example break up immiscible substances into smallerglobules and hold the globules in suspension in another liquid.

Soaps and detergents1

C

H

H

CO–Na+

OC

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HC

H

H

C

H

HH

C

H

H

Soap molecule.

2 Soap can break down to form CO2 and H2O.

3 Soap is biodegradable, breaking down within several days.

4 Detergent was produced to clean more thoroughly and function inacidic environments.

5 The first detergents were made from alkyl benzene sulfonates.

6 The first detergents were too slowly biodegradable in theenvironment.

7 Second generation detergents were costly. Adding phosphatesreduced the amount required for cleaning.

8 Today’s detergents do not contain phosphates because phosphatesadded nutrient to water courses, causing algal blooms.

9 Today’s detergents are straight chain alkyl benzene sulfonates (ABS)which are biodegradable, taking slightly longer than soap to breakdown.

Summary

Answers provided on the following page.

Summary


1 A G R I C U L T U R A L S P R A Y S

2 H Y D R O P H O B I C

3 S P H E R I C A L

4 B I O D E G R A D A B L E

5 S O A P

6 H Y D R O P H I L I C

7 S U R F A C E T E N S I O N

8 A N I O N I C

9 S U R F A C T A N T

10 I M M I S C I B L E

11 M I L K

12 E M U L S I O N

13 D E T E R G E N T

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Exercises - Part 2


Exercise 2.11 Observe a small amount of water in a small drinking glass. Draw

and label the glass and the meniscus below.

2 Pour a small amount of oil in a small, dry glass. Draw and label theglass and the meniscus below.

Refer to the Science Resource Book if you are unsure how to drawequipment scientifically.

This exercise continues on the next page.


3 Compare the strength of the adhesive force between water and glasswith the strength of the adhesive force between oil and glass.

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4 Justify the conclusion that the adhesive forces between water andglass are stronger than the cohesive forces between water molecules.

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Exercise 2.2

You should have jellybeans, snakes and toothpicks left over from a previousexperiment.

You will need:

• 2 snakes cut up into approximately 1 cm pieces (16 pieces in total)

• 4 jelly beans

• 16 toothpicks.

Follow the following steps to carry out the activity.

1 Draw a negative symbol “-” at one end of each of the 16 toothpicks.The toothpicks represent anionic surfactants or emulsifiers with anegative polar head.

Negative polar heads are attracted to water. The 16 pieces of snakerepresent water molecules.

2 Stick a piece of snake on the polar (negative) end of each toothpick.The result should be 16 surfactants (toothpicks) with their negativepolar heads buried in water (pieces of snake).

Draw one toothpick and snake pieces at this stage. Label thetoothpick as an emulsifier and the snake pieces as water molecules.

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3 Line up the four jellybeans end to end in a row. Their ends shouldbe touching. This represents oil smeared on a plate.

Draw your jelly beans below. Label them as an oil slick.

4 The non-polar end of each emulsifier is attracted to oil. Stick thenon-polar end of a toothpick into a jellybean. Repeat this with theother three jellybeans.

The result should be four toothpicks (emulsifiers) with their polarheads buried in pieces of snake (water) and their non-polar tailsburied in jelly beans (oil). The jelly beans should be arranged thesame as in step 3.

Draw your model at this stage (you should have used only four ofyour sixteen toothpicks).

Imagine you agitate the oil, just as you do as you wash up dishes.The agitation allows emulsifiers to surround the oil, breaking it intooil globules.


5 Each jellybean represents an oil globule. Separate the four jellybeans, sticking four toothpicks into each jellybean. Each oil globuleshould be surrounded with toothpicks (emulsifiers).

If you have ever played with magnets, you will know that two negativeends repel each other. This is exactly what happens to the negativelycharged heads of emulsifiers. The repelling action prevents thesurfactants from sticking together. For this reason, the oil globules theyare holding are unable to join together.

It is the repelling quality of charged emulsifiers that make them capableof holding immiscible substances in suspension eg. oil in water.

6 On the diagram below:

• label the toothpicks as emulsifiers, the jelly beans as oil globulesand the snake pieces as water

• draw the negative charges where they belong on one end of eachtoothpicks (emulsifiers)

• draw the repelling forces between the negative ends oftoothpicks (emulsifiers). Zig-zag lines might represent this well.

Model representing emulsified oil.

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Exercise 2.3

You will now make your own emulsion.

Half fill a glass jar with warm water. Place a small amount of any oil inthe water and a small amount of detergent. Place the lid on the jar andshake. You have just made an emulsion.

Tiny oil globules are held inside the liquid by the action of theemulsifiers in the detergent.

Test the oil-in-water emulsion for the characteristics listed in the tablebelow. If the characteristic is present ÷÷÷÷ the box. If the characteristic is

not present ¥¥¥¥ the box. You may need to make similar observations to

those made in Exercise 1.2.

Characteristic Solution Suspension Oil-in-wateremulsion

settling of particles ¥¥¥¥ ÷÷÷÷

residue is left after filtering ¥¥¥¥ ÷÷÷÷

light beam shone through themixture seen in the mixture

¥¥¥¥ ÷÷÷÷

1 How did you determine if particles did or did not settle in theoil-in-water emulsion?

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2 How did you determine if residue was left after filtering?

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3 How did you determine if a light beam could be seen in theemulsion?

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4 Explain the different properties of a solution, a suspension and anemulsion by using the information in the table above.

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5 Refer to Part 1 and compare the properties of a colloid with those ofthe emulsion in your table. Were they the same? Finish thefollowing sentence:

An oil in water emulsion is a ____________

Exercise 2.4

Read through Appendix 2 before attempting this exercise.

Compare the biodegradability of soaps to first, second and thirdgeneration detergents. Present your answer as a scientific discussion.(Use present or past tense language.)

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Lifestyle chemistryPart 3: Your skin


AMENDMENTS


Lifestyle Chemistry


• Mixing it up

• Your skin


• Dissolve it!

• Good medicine


Information Systems

Option

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Part 3: Your skin 1

Contents

Introduction ............................................................................... 2

The role of skin.......................................................................... 3

Investigating skin..................................................................................6

Hygiene products ...................................................................... 8

Open–ended investigation....................................................... 11

Summary................................................................................. 14

Appendix 1 .............................................................................. 17

Appendix 2 .............................................................................. 19

Appendix 3 .............................................................................. 21

Appendix 4 .............................................................................. 23


Exercises – Part 3 ................................................................... 29


Introduction

In Part 3 you will be given the opportunity to identify the three mainroles of skin, identify the parts of the skin and the common componentsof products used on the skin.

In Part 3 you will be given opportunities to learn to:

• identify the role of the skin as

– an organ to separate the body from the external environment

– an organ assisting in body temperature control

– an organ to protect against entry by disease-causing organisms

• identify and explain the use of common components of body soaps,cleansers and shampoos and the reason for their use

In Part 3 you will be given opportunities to:

• perform a first-hand investigation to examine prepared slides ofhuman skin

• identify data sources, plan, choose equipment or resources for, andperform a first-hand investigation to test a manufacturers’ claim(s)on a commercial product such as soap, shampoo or shower gel anduse the available evidence to analyse the results and discuss thevalidity of the claim(s)


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Part 3: Your skin 3

The role of skin

The skin is the largest organ in your body. It covers you from head totoe. Have you ever been frustrated with your skin’s appearance: pimples,freckles, tan, lack of tan, dryness, stretch marks, sun burn, birth marksand moles? When you discover the many functions of skin inmaintaining your health, you may feel differently about your skin.

Record as many functions of your skin as you can think of eg. protectingyour body tissues.

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The majority of information on skin is delivered on the audio tape Skin.You are required to listen to each section before carrying out activities onthe following pages.

Listen to the Role of skin section of the Skin audio tape or internet audio files(at www.lmpc.edu.au, go to Senior Science, go to Lifestyle Chemistry) andsummarise the role of the skin under each of the headings below. (Answersare not provided to questions 1-3 to encourage you to complete yoursummaries.)

1 Barrier

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2 Protection from disease

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4 Temperature control

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5 Listen to the Skin structures section of the Skin audio tape/internet audiofiles to correctly label the diagram below.

Cross section of human skin

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Part 3: Your skin 5

6 Listen again to the same audio section that you used to label thediagram on the previous page. Use the information to fill in theblank spaces in the structure and function table for parts of humanskin below.

Structure Function

top layers of the skin, protects the underlying tissue; forms abarrier from heat loss, water loss and micro-organisms

sweat gland

traps heat on the surface of the skin

hair bulb

the under skin section of hair

muscles

dermis

produces and injects melanin into surrounding cells for skinpigmentation

fibroblasts

subcutaneouslayer

produces oils to lubricate the hair and skin

sweat is released alongside coarse hair to help withevaporation

Check your answers.

Turn to Exercise 3.1 to explain the three primary functions of the skin.


Investigating skin

Focusing a microscope

Do you remember how to correctly focus a microscope? Appendix 1outlines the steps involved in focusing a microscope and a labelleddiagram of a light microscope for your review.

You are required to examine a prepared slide of human skin. To do thisyou will need to correctly focus a microscope – or at least know how ifyou do not have access to a microscope.

Turn to Appendix 2. Cut out the steps involved in focusing a microscopewhich appear in an incorrect order. Arrange the steps for focusing amicroscope in the correct order according to Appendix 1 and stick them inthe table below. (If you remember how to focus a microscope, you may notneed to refer to Appendix 1.)

Ord

er Focusing a microscope

1

2

3

4

5

6

7

8

Check your answers.

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Part 3: Your skin 7

Viewing a prepared slide

You are required to examine a prepared slide of human skin.

• If you have a microscope at home, your teacher may send you aprepared slide of human skin for you to complete Exercise 3.2a.

• If you do not have access to a microscope, it is suggested that youcomplete Exercise 3.2b. However, it is suggested you view aprepared slide when on site with your teacher.

Turn to Exercise 3.2a or 3.2b at the back of this part to draw and label aprepared slide of human skin tissue.

Complete Exercise 3.3, stating the functions of parts identified inExercise 3.2.


Hygiene products

How often do you use body soap or shampoo? Do you use a facialcleanser or do you know someone who does? Are they all emulsifiers?Do you know what they are made of?

Soaps, shampoos and cleansers all contain emulsifying agents. Theirprimary functions are to lift away oils and other contaminants, just asdescribed in Part 2. However, the components of shampoos, soaps andcleansers can differ greatly.

General ingredients in shampoos, soaps and cleansers are displayed inthe Appendix 4. You are to compare your shampoo, cleanser and soapingredients to those listed in Appendix 4. You will need a list ofingredients for the shampoo; soap; and cleanser you use at home. If youdo not have these products at home or the package listing the ingredients,choose a brand of each at the supermarket to complete the followingquestions or ask friends or neighbors for help. You will not need to buythese products. Simply answer the questions based on the labels.

Ingredients are listed from most to least in volume used. If you buybiscuits with the first ingredient as vegetable oil, you can be assured thebiscuits are fatty. The last ingredient on the ingredients list has the leastvolume in the product eg. spices in biscuits. The exception to this iswater.

1 Compare the ingredients of your shampoo with those in the Appendix 4.Record the ingredients in your shampoo that are the same as those listedin Appendix 4: Main constituents of shampoo.

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2 Use the information in Appendix 4 to state the functions of each of theingredients listed above.

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Part 3: Your skin 9

3 Did your shampoo contain many other ingredients not listed in theAppendix 4? Why do you think this is?

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_____________________________________________________

Many different substances can do similar things. Companiesproducing hygiene products rely on this to create new shampooswith different qualities. In each instance however, the function of ashampoo is to emulsify oils and other contaminants, removing themfrom the hair and scalp safely with no harmful effects.

4 List the ingredients in a cake of body soap at home.

_____________________________________________________

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_____________________________________________________

5 Refer to the Appendix 4: Main constituents of soap to record thefunction of the ingredients above.

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6 Does your soap contain substances that are not in the Appendix 4?

_____________________________________________________

7 What functions do you think each of these other substances have?

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8 List the ingredients in your cleanser that are also listed in theAppendix 2 under Main constituents of cleansers.

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Cleansers often contain many other substances to support claimssuch as: antibacterial qualities, make-up removal, deep cleansing,non-drying, moisturising, exfoliating and many more.


1 List the ingredient(s) that are common to cleansers and shampoos.

_____________________________________________________

2 What are the functions of these ingredients?

______________________________________________________

Soaps act in a similar way to the detergents you outlined above.They are both emulsifiers.

3 What are the main functions of shampoos, soaps and cleansers?

______________________________________________________

______________________________________________________

Check your answers.

Manufacturers advertise desirable qualities in their hygiene products suchas: extra body shampoos, everyday use shampoos, colour protectiveshampoos and pro-v shampoos for improving hair quality. You canprobably think of many more. Cleansers and soap manufacturers makeother claims to help sell their products.

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Part 3: Your skin 11

Open-ended investigation

You are required to carry out at least one open-ended investigationduring the HSC Senior Science course. In doing so, you must integrateand demonstrate skills, knowledge and understanding. This might sounddifficult, but each time you design and carry out an experiment, you aredemonstrating skills and each time you draw conclusions based on yourresults and knowledge, you are demonstrating understanding. Thisparticular open-ended investigation will be fun.

You are about to test the claims of a skin product or a product that comesin contact with the skin or hair. This investigation is the largest and mostdetailed investigation you will plan, carry out and report on in SeniorScience this year. Your teacher may use this open-ended investigation asan assessment task.

Think about the products in your home. Is there a shampoo that makes aclaim that you have always wanted to test like ‘improved styling’. Haveyou always wanted to test those soaps that claim to moisturise your skin?Does your dishwashing liquid really lift grease well? Do skin firmingmoisturisers really make your skin firm?

Can you think of a commercial product such as soap, shampoo or showergel, that comes in contact with the skin or hair that you could test? If youcannot think of any, ask friends and family. You may need to test theproduct against another (or several others) to gain results eg. a no-namesoap against Dove® soap; a pro-v shampoo against Pears® shampoo.

Alternative methodology could be for several people or subjects to usethe product. Their observations with regards to the manufacturer’sclaims can form your results.

Your investigation

How you approach, plan and present your investigation is for you todecide. However, the use of headings such as: aim; apparatus; method;results; discussion; and conclusion, is strongly recommended as aframework for your scientific report.


In this section you will only plan your investigation. It is suggested youplan your investigation in draft first before recording your plan forExercise 3.4.

Your plan should be sent to your teacher for review. When yourteacher is satisfied with your plan, you may begin yourinvestigation.

Your completed open-ended investigation should be handed in withPart 6, unless another date is specified by your teacher.

Be aware that your teacher may use this open-ended investigationas an assessment task.

It is essential that you contact your teacher as you complete Part 4 to gainpermission to go ahead with your plan and carry out your investigation.Remember, you must submit your completed open-ended investigationwith Part 6 unless your teacher specifies a different date.

The time taken to complete the investigation is not included as part ofthis module. Your open-ended investigation is homework.

Parts 4, 5 and 6 will contain the following reminder:

?What progress have you made towards your open-endedinvestigation from Part 3? Your report must be submittedwith Part 6 or by a date specified by your teacher.

This reminder should prompt you to call your teacher to gain approval tostart your investigation, allowing enough time to complete theinvestigation at the conclusion of Part 6.

Ideas to think about

When planning the investigation keep these questions in mind.

• Will you test the product on several people?

• How long will you need for results to be measurable?

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• How often will you test the product eg. five times a day or onceonly?

• Will you test several different products and compare their effects?

• How will you assess if the product does or doesn’t stand up to itsclaims; will you record people’s comments on the product use, ormeasure results such as relative hair volumes?

• How will you present your results?

• Will you graph your results or include photographs?

• How will you ensure the variables remain constant such as the samevolume of shampoo, the same hair types (ie. straight hair) and thesame amount of rinsing time?

When you complete your discussion and draw your conclusions, willyou:

• outline your results, relating them to what you have learned aboutsolutions, colloids, suspensions and emulsions and skin structure

• relate your results to the ingredients in the substance tested

• add additional information you have found on similar products

• suggest improvements to your experimental procedure

• suggest reasons for the experiment not working

• suggest further investigations that could be carried out?

When presenting your report, take these suggestions into account.

• Remember to use scientific language in your investigation.

• Don’t be afraid to include pictures, diagrams, graphs and tables.

• Contact your teacher as soon as you need help.

• Refer to the Science Resource Book or contact your teacher if you’renot sure how to approach the discussion and conclusion.

• Enjoy the activity.

Turn to Exercise 3.4 at the back of this part to record your plan for youropen-ended investigation.


Summary

Briefly write what you have learned under each syllabus point below.

Extracts from Senior Science Stage 6 Syllabus © Board of Studies NSW,originally issued 1999. The most up-to-date version is to be found athttp://www.boardofstudies.nsw.edu.au/syllabus_hsc/index.html

• identify the role of the skin as:

– an organ to separate the body from the external environment

______________________________________________________

______________________________________________________

______________________________________________________

– an organ assisting in body temperature control

______________________________________________________

______________________________________________________

______________________________________________________

– an organ to protect against entry by disease-causing organisms

______________________________________________________

______________________________________________________

______________________________________________________

• identify and explain the use of common components of body soaps,cleansers and shampoos and the reason for their use

______________________________________________________

______________________________________________________

______________________________________________________

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• perform a first-hand investigation to examine prepared slides ofhuman skin. (This section is left blank for you to draw a diagram.)

• identify data sources, plan, choose equipment or resources for, andperform a first-hand investigation to test a manufacturers’ claim(s)on a commercial product such as soap, shampoo or shower gel anduse the available evidence to analyse the results and discuss thevalidity of the claim(s).

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________


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Appendix 1


eyepiece

tube

nosepiece

coarse focus knob

fine focus knob

condenser adjustment knob

objective lens

stage

condenser

mirror

stage clip

Light microscope.

1 Plug in and turn on a lamp.

2 Face the lamp to the mirror.

3 Turn the nosepiece to set the objective lens on requiredmagnification eg. x10.

4 Look down the tube through the eyepiece and adjust the mirror toallow sufficient light through the tube.

5 Place a prepared slide on the stage, clipping it into place with stageclips.

6 While looking from the side, wind down the tube using the coarsefocus knob till the objective lens is almost touching the slide.


7 Look through the eyepiece, down the tube and slowly wind back thecoarse focus knob until the image comes into focus. If an image isnot seen, steps 6 and 7 should be repeated.

8 Adjust the fine focus knob to clearly focus the image.

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Appendix 2

Cut out the following steps involved in focusing a microscope and stickthem in the correct order on page 6.

Adjust the fine focus knob to clearly focus the image.

Turn the nosepiece to set the objective lens on required magnificationeg. x10.

Plug in and turn on a lamp.

Place a prepared slide on the stage, clipping it into place with stage clips.

Look through the eyepiece, down the tube and slowly wind back the coarsefocus knob until the image comes into focus.

While looking from the side, wind down the tube using the coarse focusknob till the objective lens is almost touching the slide.

Look down the tube through the eyepiece and adjust the mirror to allowenough light through the tube.

Face the lamp to the mirror.


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Appendix 3

Cross section of human skin as seen under a light microscope.Magniification x 100 (Scanned from a prepared slide © Selby. Australia.)


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Appendix 4

Main constituents of shampoo

Ingredient Function

methylparaben preservative

lauramide DEA foam stabiliser

hydrolysed animal protein conditioner/stabiliser

propylparaben preservative

cocamide DEA foam booster

ammonium lauryl sulfate detergent

sodium lauryl sulfate detergent

triethanolamine lauryl sulfate detergent

propylene glycol coupling agent

sodium laureth sulfate detergent

glycol stearate thickener/pearling agent

hydroypropyl methyl cellulose thickener

quanternium - 15 conditioner

imidazolidinyl urea antimicrobial

amphoteric – 2 detergent/conditioner

DMDM hydantoin antimicrobial

panthenol vitamin source

© ICI Australia, Chemical Fact Sheets, ICI Australia, Melbourne.


Main constituents of soap

Ingredient Function

oil (palm oil) reacts with sodium hydroxide to form soap andglycerol

sodium hydroxide reacts with oil to form soap and glycerol

glycerine (glycerol) formed in the reaction of sodium hydroxide andoil; thickener

water used to rinse the soap

sodium chloride separates glycerol from the soap

fragrance fragrance

Other substances are present or absent in different soaps to alter texture;give foaming action; moisturise; have antibacterial qualities; impartodour; act as abrasives; act as preservatives and many more. Showergels and liquid soaps contain similar ingredients to cleansers.

Main constituents of cleansers

Ingredient Function

water solvent

sodium lauryl sulfate detergent

cocamide DEA (and many othervarieties)

foam booster

glycerine thickener

citric or lactic acid pH balance

fragrance fragrance

Other substances are present or absent in different cleansers to altertexture; give foaming action; moisturise; have antibacterial qualities;impart odour; act as abrasives and many more.

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Suggested answers

The role of skin5

hair

basal layer

sebaceous gland openingmelanocyte

apocrinesweat gland

sebaceousgland

muscle thatpulls on the hair

hair follicle

vein arterynerve fibre eccrine sweatgland

epidermis

opening ofsweat gland

dermis

subcutaneouslayer

hair bulb

Labeled cross section of human skin.


6 Structure Function/s

epidermis top layers of the skin, protects the underlyingtissue; forms a barrier from heat loss, waterloss and microorganisms

sweat gland to excrete saline water, releasing body heatthrough evaporation of sweat

hair traps heat on the surface of the skin

hair bulb site of hair growth

hair follicle the under skin section of hair

muscles cause hair to become erect, trapping warm airclose to the surface of the skin, helpingtemperature regulation

dermis middle layer containing skin fibres

melanocyte produces and injects melanin into surroundingcells for skin pigmentation

fibroblasts maintains skin elasticity

subcutaneous layer consists of larger connecting veins and arteriesand fatty tissue to help insulate the body

sebaceous gland produces oils to lubricate the hair and skin

apocrine gland sweat is released alongside coarse hair to helpwith evaporation.

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1 Plug in and turn on a lamp.

2 Face the lamp to the mirror

3 Turn the nosepiece to set the objective lens on requiredmagnification eg. x10.

4 Look down the tube through the eyepiece and adjust themirror to allow sufficient light through the tube.

5 Place a prepared slide on the stage, clipping it into place withstage clips.

6 While looking from the side, wind down the tube using thecoarse focus knob till the objective lens is almost touchingthe slide.

7 Look through the eyepiece, down the tube and slowly windback the coarse focus knob until the image comes into focus.If an image is not seen, steps 6 and 7 should be repeated.

8 Adjust the fine focus knob to clearly focus the image.

Hygiene products1 Ingredients common to cleansers and shampoos are: sodium lauryl

sulfate and cocamide DEA.

2 Sodium lauryl sulfate is a detergent and cocamide DEA is a foambooster.

3 The main functions of shampoo, soap and detergents are to emulsifydirt and oils and remove them from the surface of skin or hair.


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Exercises - Part 3


Exercise 3.1

There are three main functions of skin. Provide a brief and concisedescription of these three functions.

1 _____________________________________________________

_____________________________________________________

_____________________________________________________

2 _____________________________________________________

_____________________________________________________

_____________________________________________________

3 _____________________________________________________

_____________________________________________________

_____________________________________________________

Exercise 3.2

You must complete Exercise 3.2a if you have a microscope or 3.2b if youdo not have access to a microscope. Each activity is outlined on thefollowing page.

Exercise 3.2a1 Focus a prepared slide of a cross–section of human skin tissue on

x100 magnification (this is x10 objective lens combined with the x10magnification of the eyepiece).


2 Clearly draw what you see in the circle below. If you are unsurehow to present your drawing and in what detail, refer to the ScienceResource Book or contact your teacher.

3 Use the labeled diagram of the skin on page 25 to identify and labelyour diagram of human skin tissue.

4 Write a title for the diagram and record its magnification next to thecross on the bottom right corner.

Exercise 3.2b1 Observe the diagram of a prepared cross–section of human skin

tissue under x100 magnification in Appendix 3.

2 Clearly draw what you see in the circle below. If you are not surehow to present your drawing, and in what detail, refer to the ScienceResource Book or contact your teacher.

3 Use the labeled diagram of the skin on page 25 to identify and labelyour diagram of skin tissue.

4 Write a heading for the diagram and record its magnification next tothe cross on the bottom right corner.

✗

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Exercise 3.3

Each part of human skin has a function. For three labels indicated inExercise 3.2, state their functions below.

Part Function

Exercise 3.4

Plan your open-ended investigation below. You should make a roughcopy on separate paper first. Include attachments with this exercise ifthis section is not large enough for your plan.

Keep a copy of your plan for you to follow as you carry out yourexperiment over the coming weeks. Perhaps you could keep ajournal.

Aim

What are you trying to find out? What product(s) are you testing?

_________________________________________________________

_________________________________________________________

_________________________________________________________


Apparatus

What and or who will you need to carry out your investigation?

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

Method

How will you carry out your investigation? Organise each stepsequentially and either number or dot point the steps. How will youcollect results? Will your data be quantitative (measured) or qualitative(compared against each other)?

Indicate your dependent and independent variables. Outline how youwill ensure controlled variables are kept constant and what your controlwill be. It is essential these points are covered. If you are unsure of theseterms refer to the Science Resource Book or contact your teacher.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

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Results

How will you present your results? Will you use a table? Will youinclude photographs or draw a graph? Include a plan showing how youwill record your results. You may include a rough sketch of a graph youare expecting to draw.

You must indicate if your results are to be quantitative (measured) orqualitative (compared against each other). If you do not understand themeaning of these terms, refer to the Science Resource Book or contactyour teacher.

Don’t forget to keep a copy of your plan. You will need to followit while conducting your open-ended investigation.

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Lifestyle chemistry

Part 4: What’s growing on your skin?


AMENDMENTS


Lifestyle Chemistry


• Mixing it up

• Your skin


• Dissolve it!

• Good medicine


Information Systems

Option

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Part 4: What’s growing on your skin? 1

Contents

Introduction ............................................................................... 2

The microflora of skin ................................................................ 3

Microbe colonisation ............................................................................9

Breaking the barrier............................................................................10

Acidity and alkalinity ................................................................ 11

The pH scale ......................................................................................12

The pH of skin ......................................................................... 14

Skin and hair products .......................................................................16

Testing skin and hair products...........................................................17

Summary................................................................................. 20

Appendix 1 .............................................................................. 21

Appendix 2 .............................................................................. 22


Exercises – Part 4 ................................................................... 27


Introduction

Your skin is host to a great number of micro-organisms. They live onskin oils, proteins and sweat. Your first instinct might be ‘Yuck! Get ridof them!’ However, these microbes play an important role in bodydefence. The skin and hair products you use must be compatible with theskin’s natural defense or damage and infections can result.

In Part 4, you will be given the opportunities to learn to:

• define the term microflora and discuss the role of the microflora onskin in different parts of the body

• discuss the term pH in terms of its ability to describe the acidity of asubstance

• explain the relationship between the natural pH of the skin and theaction of

– microflora

– natural oil produced by glands in the skin

– perspiration.


• perform first-hand investigations to measure the pH values of arange of skin and hair products.


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The microflora of skin

The term microflora is an odd term. You should understand the term‘micro’. It means very small or microscopic in size. You are not able tosee micro-organisms with the naked eye. The second part of the termmicroflora is ‘flora’. What would you normally associate the term florawith? Think about florists, floral patterns, flora and fauna. Have youdecided what flora should mean? Your answer should have been‘plants’. Automatically your brain should think that microflora meansmicroscopic plants, right? Wrong!

In this instance, flora appears to take on the meaning of an ecosystem ora group of organisms surviving together. For this reason, the termmicroflora is defined as microorganisms surviving as microscopiccommunities.

1 Write the correct definition for microflora in the box below.

Your mouth, nose and ears all contain different varieties of microflora.Most microflora on and in the body are bacteria. You will be researchingthe natural microflora existing on the surface of your skin and what theireffects are.


2 Use the glossary to define the following terms as they will help youunderstand the Microflora section of the Skin audio tape/internetaudio files.

bacteria _______________________________________________

______________________________________________________

staphylococci __________________________________________

______________________________________________________

cocci _________________________________________________

______________________________________________________

microbes ______________________________________________

______________________________________________________

micro-organisms ________________________________________

______________________________________________________

sebum ________________________________________________

______________________________________________________

epidermis _____________________________________________

______________________________________________________

keratin ________________________________________________

______________________________________________________

Think about the skin on different parts of your body. Colour the parts of thebody below where you think bacteria might exist. Remember, you arefocusing on where bacteria might exist on the surface of your skin.

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You will see how accurate your predictions were as you listen to thefollowing audio.

Listen to the Microflora section of the Skin audio tape/internet audio files,then carry out the activities which follow. You may need to listen to thetape several times in order to answer all the questions.

3 Why is skin not considered to be uniform?

_____________________________________________________

_____________________________________________________

4 What conditions favour the growth of micro-organisms?

_____________________________________________________

_____________________________________________________

5 All organisms require nutrients to live. What nutrients are availableon the skin surface for micro-organisms to utilise?

_____________________________________________________

6 Why is the skin an unstable site for microbes to colonise?

_____________________________________________________

_____________________________________________________

_____________________________________________________

7 What effects can the action of microflora have on the skin surface?

_____________________________________________________

_____________________________________________________

_____________________________________________________

Appendix 1 contains a species list of microflora found on the surface ofhuman skin. Use this list to help you spell the species names stated in theaudiotape for the following question.

Word processed genus and species names are italicizedeg. Staphylococcus aureus. The first name is the genus name and muststart with a capital letter. The second name is the species name andbegins with a lower case letter. You might remember from preliminarywork that when hand writing genus and species names, you mustunderline each separately eg. Staphylococcus aureus. Do this for thespecies column for question 8 on the following page.


8 List the species of microflora in the table below and indicate wherethey are commonly found on the body. Disregard the centre columnas you will complete this with question 9. The first one has beendone for you.

Species of microflora Group Part of body found

Staphylococcus epidermidis upper body

9 Classify each of the micro-organisms identified above into groups.The classifications are: bacteria, fungi and mites. Write these namesin the middle column in the above table. All cocci and bacilli areforms of bacteria. Mould and yeast are forms of fungus. Refer toAppendix 1 to help you classify each species.

10 Look at the diagrams of cocci, bacilli and moulds on the followingpage, then answer the following questions.

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coccus

staphlococcus

diplococcus

Examples of cocci bacteria viewed under a highpowered microscope.

Examples of bacilli bacterium under a high poweredmicroscope.

Example of a mould under a light microscope (not ashigh powered).

10 a) What do the diagrams of cocci bacterium look like to you?

_________________________________________________

_________________________________________________

b) Describe what bacilli look like in one sentence.

_________________________________________________

_________________________________________________


c) Explain the difference between moulds and bacteria whenviewed under a microscope.

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

11 For each of the body parts inhabited by microflora in question 8,indicate the microflora present on the diagram of a person on thefollowing page.

The places where particular species of microbes are found on human skin.

Check your answers.

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Microbe colonisation

More recent studies have found that microflora of the skin can be dividedinto two groups: resident microflora and transient microflora.

Resident microflora are found on the skin surface and are thought toreside in the sebaceous glands under the skin. Bacterial counts are higherwhere more oil is being produced by sebaceous gland activity. Residentbacteria such as Staphylococcus epidermidis are thought to play animportant role in protecting the individual from more pathogenic ordisease-causing bacteria. It has been found that an area of skin colonizedby relatively harmless bacteria inhibits the growth of other microbes. Inthis way, the body is protected from skin diseases and disorders by themicrobes living on the skin surface.

Transient microflora have two sources. The first source is the externalenvironment eg. soil, water and air. Contact with soil, water and airtransfers any microbes present to the skin surface. The second source isthe natural microflora that comes out of body orifices such as the nasalpassages, ear canals and anus. Micro-organisms are transferred tovarious parts of the body by the hands. Once these organisms aretransferred to a suitable site, they can flourish. Transient microbes cancause diseases such as diarrhoea and meningitis.

Washing with soaps and detergents removes many surface microbes,along with a great deal of the oily protective layer. However theremaining resident microbes quickly grow and reproduce to colonise the‘clean’ skin, restoring the natural microflora of the skin.


Breaking the barrier

Have you ever had a rash or skin irritation? Your skin defence couldhave been breached. Have you ever had tinea on your feet? If so, yourskin defence has been breached. There are many ways your skin defensecan be broken. You may have recently broken your skin defense barrierwithout realising.

Have you burnt or cut yourself recently? You may have shaved an areaof skin; grazed yourself; or handled chemicals such as turps withoutgloves. All these common activities can alter the protective layer of skin.A change in diet can cause a change in skin acidity, lowering yourdefense to harmful micro-organisms. Even washing can remove naturalmicroflora, allowing more harmful microbes to colonise the area.

Has your skin become damaged over the last two weeks? Record thedamage, how it occurred, the part of the body and any resultant infections orskin irritations that occurred.

Damage to skin How the skinwas damaged

Part of the body Resultinginfections orirritations

As you have seen, the protective skin barrier is easily damaged. Harmfulmicrobes living on the skin surface can easily penetrate a wound, causingan infection.

The use of products that are incompatible with the skin surface can causeskin damage, alter the natural acidity of the skin or alter the naturalmicroflora of the skin.

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Acidity and alkalinity

Carry out the following activity to review pH in terms of acidity andalkalinity.

1 a) Write the numbers 0 to 14 on the scale below.

b) On the line next to ‘7’, after the arrow, write neutral pH.

c) On the line next to ‘1’, write strongly acidic.

d) On the line next to ‘14’, write strongly alkaline.

e) Next to the arrow pointing up, write increasing acidity.

f) Next to the arrow pointing down, write increasing alkalinity.

0 __________________________________________

≠ ____________________________________

Æ ____________________________________

Ø ____________________________________

14 __________________________________________

Well done. You just created a pH scale.


The pH scale measures acidity and alkalinity from 0 to 14. From theprevious activity you should understand that a pH number lower than 7indicates an acid and a number greater than 7 indicates an alkali. A pHof 7 is neutral. Most organisms prefer to live in pH neutral conditions (7)as acids and alkalis tend to damage cells and destroy tissue.

A pH of 4 is more acidic than a pH of 6. A pH of 10 is less alkaline thana pH of 12. The stronger the acid or alkali, the more dangerous it is as ithas the ability to corrode substances.

0-2 is a strongly acidic; 3-4 is an acid; 5-6 is weakly acidic; 7 isneutral; 8-9 is weakly alkaline; 10-11 is alkaline; and 12-14 isstrongly alkaline solution.

2 Indicate the acidity or alkalinity of the following pH values using theabove information.

a) 4 _________________________________________________

b) 6 _________________________________________________

c) 13 ________________________________________________

d) 10 ________________________________________________

e) 7 _________________________________________________

f) 9 _________________________________________________

g) 1 _________________________________________________

Check your answers.

The pH scale

You may have received some pH paper from your teacher with this part.pH paper turns a different colour depending on the acidity or alkalinity ofthe substance it is testing.

You will be investigating the pH range 1 - 11. You will need to matchyour pH paper with a colour to determine the pH of the substance you aretesting.

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You are about to create a colour scale by which you can gauge colourchanges in the pH paper. Use coloured pencils or textas to colour in theblank boxes below with the shade indicated below each box. You may needtwo different colours to create the correct shade in each box.

Sh

ade

Co

lou

r

mar

oon

red

deep

ora

nge

oran

ge

light

ora

nge

yello

w/m

usta

rd

light

gre

en

gras

s gr

een

dark

gre

en

deep

blu

e/gr

een

dark

blu

e

pH 1 2 3 4 5 6 7 8 9 10 11

You will be using the colour scale you just made for experiments later inthis part. You may need some practice to read the correct pH from thescale and determine if it indicates acidity or alkalinity or neutrality.

State the pH of the following shades of pH paper and the acidity oralkalinity they indicate. You may use the boxed information on page 12 tohelp you determine acidity and alkalinity. The first one has been done foryou as a guide.

Shade of pH paper pH Acidic/alkaline

dark green 9 weakly alkaline

orange

deep blue/green

deep orange

light green

maroon

yellow/mustard

Check your answers.


The pH of skin

Do you recall seeing lipsticks in shops that are green or blue, but changecolour when you apply them? The lipsticks change colour due to theacidity of the skin.

Often two people can apply the same lipstick, but it will turn a differentcolour on each person due to the different acidity levels of each person’sskin. This lipstick is not to be confused with normal lipstick which staysthe same colour when applied.

Many factors can affect the pH of your skin.

Listen to the Skin pH section of the Skin audiotape/internet audio files. Youmay need to listen to the tape several times to answer the followingquestions.

1 What is the normal pH range of human skin?

_____________________________________________________

2 Explain the normal pH range in terms of acidity and alkalinityeg. strongly acidic to alkaline.

______________________________________________________

3 What main factor causes skin to become acidic?

______________________________________________________

______________________________________________________

4 What parts of the body have different pH values?

______________________________________________________

______________________________________________________

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5 Are the pH values that are commonly associated with the parts of thebody outlined in question 4 higher or lower than the rest of thebody? Does this mean they are more acidic, more neutral or morealkaline?

_____________________________________________________

_____________________________________________________

6 Are more or fewer microbes associated with the underarms,forehead, toe webs and the soles of the feet?

_____________________________________________________

_____________________________________________________

7 There are two theories why the underarms, forehead, toe webs andthe soles of the feet have higher pH values. Explain those twotheories below.

a) _________________________________________________

_________________________________________________

_________________________________________________

b) _________________________________________________

_________________________________________________

_________________________________________________

8 What is the acid mantle?

_____________________________________________________

_____________________________________________________

9 What is thought to be the function of the acid mantle?

_____________________________________________________

_____________________________________________________

10 Some scientists believe that the acid mantle has little to do with themicroflora of skin. What do they suggest has a greater impact onmicrobe populations on the skin surface?

_____________________________________________________

_____________________________________________________

Check your answers.


Turn to Exercise 4.1 at the back of this part to discuss the role of microflorain different parts of the body.


Skin and hair products1 Fill in the missing words in the passage below.

Imagine you are a microbe living on a person’s face. You arecomfortable living with a pH of 6. Suddenly, the person_______________ their face with a substance that has a pH of 8.The skin has changed from weakly _________________ to weakly____________________. You and your friends cannot survive above apH of 7.5. You die, along with your friends. The skin surface is nolonger acidic. The ______________ mantle has been altered. Different___________________ are more able to colonise the area you were livingon. They may cause _____________________ on the skin surface.

Write the questions for the following answers.

2 ______________________________________________________

______________________________________________________

Your clean skin could become colonised by different, microbes if thepH was changed. These microbes could cause disease.

3 ______________________________________________________

______________________________________________________

Products used on the skin should have a similar pH to that of skin tominimise disruption of the acid mantle. The acid mantle protects theskin from colonisation by harmful organisms.

4 ______________________________________________________

______________________________________________________

Substances that are acidic or alkaline have the ability to destroyliving tissue. Products used on the skin with a pH below 5 or above9 have the ability to damage the skin. The protective layer of skincan allow the entry of harmful organisms once damaged. Rashes,skin irritations, infections and disease can result.

Check your answers.

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Testing skin and hair products1 Next to the bullet points below, write down all the skin and hair

products you have at home. Include as many as you can such as: soaps;cleansers; shampoos; deodorant, hair spray; ointments; heat rub;shaving cream; moisturisers; perfume; sunscreen after shave; andlipsticks. You may need to ask your family what products they use ontheir skin.

Do not include dry substances such as eye shadow and blusher as theyare not moist enough to change the colour of the pH paper.

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

Were you surprised at the range of hair and skin products in your house?Did you have enough room to record them all?

Skin and hair products are used by people on a daily basis. Have youever thought about how compatible these substances are with your skin?Do you think they could have the ability to damage your skin or loweryour defence to infection?

You are about to test the pH of skin and hair products in your home andevaluate their compatibility with skin pH.

Aim

To measure the pH values of a range of skin and hair products.

Apparatus

• Approximately 20 cm of universal pH paper from your teacher.

• The pH colour scale from page 13 or the one supplied with pH paper

• Ten skin and/or hair products.

• Ten cotton buds or pop sticks (ice cream sticks).


Method

1 Collect ten or more skin and hair products from around the house.You listed these earlier. Record the product type and brand for eachof the substances.

2 Being careful not to wet or contaminate the pH paper, roll it out ontop of a sheet of paper or absorbent paper. The paper will protect thetable surface.

You may need to weighdown each end of the pHpaper to keep it flat. If youhave pieces of pH paperinstead of a length of paper,place these on a clean A4sheet of paper.

You will need to keep trackof what substance is beingtested on what part of pHpaper. Write the substanceon the paper next to the pHpaper. Refer to the diagramopposite.

3 Dip a cotton bud or a pop stick into the first substance to be tested.Remove any excess and dab the substance onto the place allocatedon the pH paper. Be careful to apply only a small amount of thesubstance as the substance may spread, contaminating other sections.

Use a different cotton bud or pop stick for each substance beingtested.

Some substances may need to be wetted first or lathered beforesampling eg. soap. If so, be careful not to contaminate the pH paperwith water drops or wet hands.

4 Repeat step three with the remaining substances.

5 When all substances have been applied, use your pH colour scalefrom page 13 to determine the pH of each substance. Record thesein the results table.

Some substances such as foundation may mask the pH colour.Try turning the pH paper over to observe the colour absorbedunderneath.

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Results

Complete your results in the table below. An example is provided.

Skin or hair product Brand pH colour pH

soap sunlight yellow/mustard 6

Discussion

Fill in the missing pH values and product names based on your results.

a) The substances tested ranged from ________ to ________ in pH.

b) ______________________________ was the most acidic substance

with a pH of ________ and ______________________________

was the most alkaline substance with a pH of ________.

c) Generally the hair products tested range in pH from ________ to_______.

d) pH values of the skin products tested range from _______ to_______.

Turn to Exercise 4.2 at the back of this part to draw your conclusions on thepH values of a range of skin and hair products.



Summary

1 Write three things you are unsure of about skin microflora

______________________________________________________

______________________________________________________

______________________________________________________

2 What do you need to do to gain an understanding about those pointsoutlined in question 1?

______________________________________________________

______________________________________________________

3 Write three questions you would ask your teacher about the pH ofskin if you were in class and did not fully understand the concept.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

4 What do you need to do to gain an understanding about those pointsoutlined in question 3?

______________________________________________________

______________________________________________________

5 a) What pH ranges do the skin and hair products have that youtested?

__________________________________________________

b) How compatible are these pH ranges with skin pH?

__________________________________________________

__________________________________________________

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Appendix 1

Microbes commonly detected on human skin

Gram-positive bacilli

Corynebacterium jeikeium

Corynebacterium urealyticum

Corynebacterium minutissimum

Propionibacterium acnes

Propionibacterium avidum

Propionibacterium granulosum

Brevibacterium epidermidis

Gram-negative bacilli

Acinetobacter calcoacaticus

Yeasts (Fungi)

Malassexia furfur

Moulds

Trichopyton mentagrophytes

Mite

Demodex folliculorum

Gram-positive cocci

Staphylococcus aureus

Staphylococcus auricularis

Staphylococcus capitis

Staphylococcus cohnii

Staphylococcus epidermidis

Staphylococcus haemolyticus

Staphylococcus hominis

Staphylococcus saccharolyticus

Staphylococcus saprophyticus

Staphylococcus simulans

Staphylococcus warneri

Staphylococcus xylosus

Micrococcus luteus

Micrococcus lylae

Micrococcus nishinomiyaensis

Micrococcus kristinae

Micrococcus sedentarius

Micrococcus roseus

Micrococcus varians


Appendix 2

Example answer to Exercise 4.21

Include your used pH paper as shown above.

3 The skin and hair products tested ranged in pH from 5 to 7. Productswithin a pH range of 4 to 8 are compatible with skin as skin has a pHrange of 4 to 8, however most skin has a pH of 5.5 to 6. Themoisturisers, deodorants, soaps and hand creams tested arecompatible with skin. Any substances used on skin with pH valuesbelow 4 and above 8 have the potential to change skin pH, thusaltering the acid mantle. This could allow colonisation of the skinsurface by harmful micro-organisms and result in skin irritation orinfection.

This answer is fictitious and does not indicate actual pH ranges of skin and hairproducts.

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Suggested answers

The microflora of skin1 Microflora means micro-organisms surviving as microscopic

communities.

2 Bacteria: single-celled procaryotic organisms belonging to the protistkingdom.

Staphylococci: cocci bacteria appearing in grape-like formations.

Cocci: sphere-shaped bacteria.

Microbes: micro-organisms.

Micro-organisms: microscopic, often single-celled, organisms.

Sebum: oil produced by sebaceous glands in the dermis.

Epidermis: outermost layer of the skin which protects the underlyingtissue, forms a barrier from heat loss, water loss andmicro-organisms.

Keratin: tough protein present in the epidermis of vertebrateorganisms.

3 Skin varies from dry areas to moist areas and wet areas, thereforeconditions on the skin surface are not uniform.

4 Micro-organisms prefer moist environments.

5 Sweat from sweat glands contains sodium chloride and lactate.Sebum, an oily substance from sebaceous glands next to hairfollicles, also provides nutrients that encourage micro-organisms.

6 The skin surface is constantly losing clumps of dead skin. Anymicrobes on the skin surface are lost. The pH of skin is slightlyacidic – at 5.5 pH. Most microbes prefer a pH neutral environmentof 7. For these reasons, only specific microbes are able to survive onthe skin surface.

7 The action of microflora on the skin causes the oil on the skin tobecome acidic. Microbial action on sebum releases smelly gases,commonly referred to as body odour.


Species of microflora Group Part of body found

Staphylococcus epidermidis bacteria upper body and face

8,9

Staphylococcus hominis bacteria legs and arms

Micrococcus luteus bacteria head, legs and arms

Corynebacterium jeikeium bacteria arm pit

Propionibacterium acnes bacteria face and shoulders

Propionibacterium avidum bacteria arm pit

Propionibacterium granulosum bacteria side of nose

Brevibacterium epidermidis bacteria in between toes

Acinetobacter calcoaceticus bacteria groin and front of elbow

Malassezia furfur fungus scalp, ear and back

Trichophyton mentagrophytes fungus feet

Demodex folliculorum mite face

10 a) Cocci look like small round spheres like ball bearings.Staphylococci resemble a bunch of grapes. (Other answers areacceptable.)

b) Bacilli look like small rods. One bacillus resembles a chainwith rods linked together. (Other answers are acceptable.)

c) Moulds have threads joining each mould head containingspores. Bacteria are much smaller, needing a higher powermicroscope for viewing and are individuals or groups of spheresor rods.

11 Refer to the table above to locate areas particular species ofmicrobes are found.

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Acidity and alkalinity1

0 strongly acidic

1

2

3

4

5

≠

6

increasing acidity

7 neutral pH

8

Æ9

10

11

12

13

Ø increasing alkalinity

14 strongly alkaline

2 a) 4 is acid

b) 6 is weakly acidic

c) 13 is strong alkaline

d) 10 is alkaline

e) 7 is neutral

f) 9 is weakly alkaline

g) 1 is strongly acidic

The pH scale

Shade of pH paper pH Acidic/alkaline

orange 4 acidic

deep blue/green 10 alkaline

deep orange 3 acidic

light green 7 neutral

maroon 1 strongly acidic

yellow/mustard 6 weakly acidic


The pH of skin1 The normal pH range of human skin is 4 – 8.

2 The normal pH range of human skin is acidic to weakly alkaline.

3 Sweat released from sweat glands is released at a pH of 5, causingthe skin to have an acidic surface.

4 The underarms, forehead, between the toes and the soles of the feethave different pH values than the skin on the rest of the body.

5 The underarms, forehead, between the toes and the soles of the feethave slightly higher pH values, meaning they are more neutral thanthe rest of the body.

6 More microbes are associated with the underarms, forehead, toewebs and the soles of the feet than the rest of the body.

7 a) The high microbe populations metabolise sweat, sebum andkeratin. Their wastes cause the higher pH levels.

b) Sites such as the underarm are moist and separate to the rest ofthe body. For this reason, the pH is higher and more microbesare able to survive there as a result.

8 The acid mantle is the protective layer on the surface of the skin.

9 The acid mantle is thought to prevent more microbes fromcolonising the skin surface, as most microbes prefer a neutral pH.

10 Some scientists suggest that electrostatic forces between the skinsurface and microbes determines skin microflora populations morethan the acidity of skin.

Skin and hair products1 Imagine you are a microbe living on a person’s face. You are

comfortable living with a pH of 6. Suddenly, the person washestheir face with a substance that has a pH of 8. The skin has changedfrom weakly acidic to weakly alkaline. You and your friends cannotsurvive above a pH of 7.5. You die, along with your friends. Theskin surface is no longer acidic. The acid mantle has been altered.Different microbes are more able to colonise the area you wereliving on. They may cause disease on the skin surface.

2 What could happen to your skin if the pH was changed due tocleaning products?

3 Why is it important that products used on the skin be a similar pH tothe skin surface?

4 What result could products used on the skin have if they have a pHlower than 5 or greater than 9?

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Exercises - Part 4


Exercise 4.1

Choose two of these body parts:

• face • arm • underarm

• scalp • back • feet (and toes).

For each of the two body parts you chose:

• state all the species of microflora present on the skin in that part ofthe body (if you chose the arm, you must include the species existingon the inside of the elbow)

• clearly draw an example of one of those species, indicating thespecies name (the species name must be scientifically written)

• explain the source of nutrients for the micro-organisms on that partof the skin

• explain the effects of microorganism activity eg. smell, acidenvironment.

a) • body part

_________________________________________________

• species of microflora present

_________________________________________________

_________________________________________________

• diagram and label of one microorganism present at this site.


• source of nutrients

__________________________________________________

__________________________________________________

• effects of micro-organism activity

__________________________________________________

__________________________________________________

__________________________________________________

b) • body part

______________________________________________________

• species of microflora present

______________________________________________________

______________________________________________________

• diagram and label of one microorganism present at this site

• source of nutrients

______________________________________________________

______________________________________________________

• effects of micro-organism activity

______________________________________________________

______________________________________________________

______________________________________________________


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Exercise 4.2a) Attach your pH paper with this section complete with product

names. Appendix 2 includes a graphic showing what your teacherexpects. Put the pH next to the name of each substance tested orinclude a results table with this information.

b) Comment on the accuracy of your pH readings of differentsubstances used on the skin given that you made your own pH scale.

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

c) Most skin has a slightly acidic pH of 5.5 or 6. You have tested thepH values for a range of skin and hair products. In the spaceprovided:

• outline the range of pH values you observed

• discuss the compatibility of skin and hair products with regardsto pH

• outline possible consequences of skin and hair products that aretoo acidic or too alkaline.

You may refer to Appendix 2, which provides an example answer tothis exercise.

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

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Lifestyle chemistry

Part 5: Dissolve it!


AMENDMENTS


Lifestyle Chemistry

• Common substances

• Mixing it up

• Your skin


• Dissolve it!

• Good medicine


Information Systems

Option

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Part 5: Dissolve it! 1

Contents

Introduction ............................................................................... 2

Solvents .................................................................................... 3

The universal solvent ...........................................................................4

Alcohol as a solvent .............................................................................8

Solvent properties ..............................................................................11

Cosmetics and external medications....................................... 12

Subdermal implants ...........................................................................14

The digestive system............................................................... 16

Summary................................................................................. 19

Appendix 1 .............................................................................. 21

Appendix 2 .............................................................................. 23

Appendix 3 .............................................................................. 25


Exercises – Part 5 ................................................................... 31

2 Lifestyle Chemistry

Introduction

Have you ever wondered why some substances dissolve in water whilstothers do not? In Part 5 you will be given opportunities to learn thechemistry behind the solubility of substances; the common substancesthat contain solvents; and how different types of tablets and medicalimplants regulate the released of medication over time. The nature of thedigestive system is also outlined.


• identify water and alcohol as commonly used solvents

• explain the relationship between the properties of solvents and theiruse in cosmetics and external medication

• identify cosmetics and external medications where water is thesolvent

• identify cosmetics and external medications where alcohol is thesolvent

• identify the parts of the digestive system

• outline the role of the stomach and the small intestine in breakingdown food

• discuss the difference in pH of the stomach and the small intestine.


• identify data sources, gather, process, analyse and presentinformation from secondary sources to identify how subdermalimplants release their medication into the body.


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Solvents


1 Do you remember the term solvent from Part 1? Write the definitionfor a solvent below.

_____________________________________________________

_____________________________________________________

You may not realise that you rely on solvents every day. You wouldn’tbe able to make a cup of tea or a milkshake or toffee without a solvent.You wouldn’t be able to wash your paintbrushes or take medicinewithout it. Soft drink wouldn’t even exist without a solvent.

2 There are two common solvents. Use the clues below to identify thetwo solvents.

a) This solvent can dissolve sugar and salt, is very common andquenches your thirst. Without this solvent, you wouldn’t be ableto make a cup of tea or swim in a pool.

_________________________________________________

b) This solvent is found in nail polish remover and methylatedspirits. It can cause people to act strangely and is regularlyconsumed at parties. It begins in a and ends in l.

_________________________________________________

Check your answers.


The universal solvent

Have you ever wondered why water is capable of dissolving samesubstances and not others? The chemical concept is not as hard tounderstand as it seems.

Water is the universal solvent. It has the ability to dissolve manysubstances.

You should be familiar with the chemical formula for water, H2O.This means that each water molecules contains two hydrogen atoms andone oxygen atom.

1 On the diagram of a watermolecule opposite, draw a ‘+’next to each hydrogen atom anda ‘–’ next to the oxygen atom. H

OH

Check your answer before moving on.

2 a) Draw an oval shapearound the water moleculeopposite.

b) Outside the circle on theside with the oxygenmolecule, write a ‘–‘symbol. This side of themolecule has a slightlynegative charge.

c) On the side with thehydrogen atoms, write a‘+’ symbol. This side ofthe water molecules has aslightly positive charge.

HO

H


You have just drawn a water molecule with polar ends. This means thatcertain ends of the molecule contains a positive or negative charge.

Water molecules are polar.

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3 Imagine a water molecule is like a magnet. One end is positive andthe other end is negative. If you have five magnets, the positive endof each magnet will be attracted to the negative end of another. Thewater molecules below are attracted to each other like magnets.Some charges are displayed on the molecules. Write in theremaining charges. (Remember positive and negative charges areattracted to each other.)


If water molecules did not have polar ends, water molecules would notstick together and life as we know it could not exist.

The strong forces between water molecules are called cohesive forces.When another substance is added to water with stronger attractive forcesthan the water molecules themselves, the water molecules will beattracted to the new substance, thus dissolving it. This can be likened toa group of girls at a disco.

Imagine a group of girls sticking together at a disco as water molecules.The forces holding them together are cohesive forces of positive andnegative attraction. When a group of guys are added to the disco, thegirls might be more attracted to them than each other. If you stillimagine the girls as polar water molecules, they disperse, each becomingattracted to a boy.

Sugar like water has OH groups. Parts of the molecule is polar.Therefore, sugar can dissolve in water.

Non polar substances dissolve in other non-polar substances. polarsubstances dissolve in polar substances.

Are you confused? If so, you are about to carry out an activity thatshould help.


4 Cut out the girl water molecules and boy sugar molecules fromAppendix 1. The girls have their arms out representing the polar ends ofa water molecule. One arm represents the positively charged end andthe other represents the negatively charged end of a water molecule.The boys also have their arms out, representing the polar parts of sugarmolecules.

The positive ends of water molecules (girls) are attracted to the negativepart of sugar molecules (boys) and vice versa.

Two girls (molecules of water) are attracted to each end of a boy (sugarmolecule). This causes each boy to be surrounded by a ‘jacket’ of fourgirls.

Remembering positive and negative charges attract, arrange the waterand sugar molecules from Appendix 1 so that four water molecules(girls) are holding onto each sugar molecule (boy).


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By now, you should understand that:

• each water molecule contains two hydrogen atoms and one oxygenatom

• water molecules are polar with one end positively charged and theother end negatively charged.

• water molecules are attracted to each other with cohesive forces

• polar substances will dissolve in water

• the polar ends of a substance are attracted to the polar ends of watermolecules, causing the substance to dissolve in the water.

• a substance that is not polar will not dissolve in water.

If you do not understand the points outlined above, contact your teacher forhelp before moving on.

Cordial, sugar in water, salt in water; tea and most disinfectants areexamples of substances with water as a solvent. It is also used todissolve acids and alkalis. Your swimming pool uses water as a solvent,salt and/or chlorine is dissolved in the water.

Even though water is referred to as the universal solvent, it is not as easyto think of examples where water is used as a solvent only. You couldprobably think of many examples where water is used as a base forcolloidal mixtures and suspensions. Water is used in soft drink as asolvent.

5 Identify four substances where water is used as a solvent.

_____________________________________________________

_____________________________________________________

Check your answers.



Alcohol as a solvent

There are many different forms of alcohol. You may have heard ofglycerol, ethanol, methanol and phenol. These are just a few forms ofalcohol. The alcohol you are probably the most familiar with is in beer,wine and spirits. These all contain ethanol. Methylated spirits is mainlyethanol but is rendered undrinkable by the addition of methanol which ispoisonous in small quantities.

You have learnt about the polar nature of water and why it dissolvespolar substances. The alcohols you will be investigating are mainlyethanol and methanol. These alcohols differ greatly from water as theyare only slightly polar at one end and non-polar at the other end. Thismeans that one end of the molecule possesses a charge and the other endof the molecule has no charge.

List as many substances containing alcohol that you know of. For example,your list may contain alcoholic drinks or substances used on the skin.

_________________________________________________________

_________________________________________________________

_________________________________________________________

Ethanol and methanol

Ethanol is a widely used solvent. Look at the structure of an ethanolmolecule below. ‘C’ represents carbon atom, ‘H’ represents a hydrogenatom and OH represents oxygen and hydrogen combined as a hydroxidegroup.

H C

H

H

C

H

H

OH

The chemical structure of ethanol.

The hydroxide (OH) end of an alcohol molecule is slightly polar, havinga slight charge. The other end is not polar, having no charge.

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1 Draw a molecule of ethanol below. On the hydroxide (OH) end of themolecule write slightly polar. On the other end of the molecule, writenon-polar.

2 With one polar end and one non-polar end the alcohols, methanoland ethanol have interesting capabilities. Break the code below todetermine these capabilities.



the polar end can dissolve in water and the non-polar endcan dissolve in oil

Write your complete answer in the box below.

Check your answers before moving on.

Larger alcohol molecules

Most of a larger alcohol molecule consists of a hydrocarbon chain madeup of carbon and hydrogen atoms only. This means that larger moleculesof alcohol such as cetyl alcohol are mostly non-polar. They can dissolvenon-polar molecules.

Because most of a larger alcohol molecule dissolves in oil and the restdissolves in water, alcohol can be used as an emulsifier between oil and


water. This has many applications especially in the cosmetics industry.These are discussed later in this part.

By now, you should understand that:

• ethanol and methanol have a slightly polar end and a non-polar end

• the polar ends of ethanol and methanol alcohols are able to dissolvein water

• the non-polar ends of ethanol and methanol alcohols are able todissolve in oil

• in larger alcohol molecules the polar OH group is only a small partof the larger alcohol molecule

• polar substances can dissolve in small alcohol molecules likemethanol and ethanol but not larger alcohol molecules like cetylalcohol

• substances that are weakly polar or non-polar will dissolve inalcohols because most of any alcohol molecule is non-polar

• substances dissolving in alcohol are dispersed through the alcohol.

If you do not understand the points outlined above, contact your teacher forhelp before moving on.

Alcohols are used as solvents in textas, methylated spirits, stainremovers, imitation vanilla essence, antifreeze, enamel paints, varnishes,mouth wash, cough mixtures, perfumes, after shave and nail polishremover.

Identify four substances where alcohol is used as a solvent.

_____________________________________________________

_____________________________________________________

_____________________________________________________

Check your answer.

Turn to Exercise 5.1 at the back of this part to identify different solvents.

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Solvent properties

An interesting quality of the alcohols commonly used as solvents,methanol, ethanol and propanol, is that they evaporate quickly. If analcohol is used on the skin surface, it feels cool and soothing. This isbecause it removes body heat as it evaporates, leaving the skin with a‘cool’ sensation. In high enough quantities, alcohol also has the ability todehydrate the cells of microbes, causing them to die. Antiseptics anddisinfectants rely on this property of alcohol to kill bacteria.

You have also already learnt that some alcohols can be used assurfactants and emulsifiers as some have a polar and a non-polar end.

1 Use the points below to record three properties of alcohol from thepassage above.

• __________________________________________________

__________________________________________________

• __________________________________________________

__________________________________________________

• __________________________________________________

__________________________________________________

Water has the ability to dissolve polar substances. You may only beaware of table salt, however, there are many other salts that dissolve inwater. Acids, alkalis and the alcohols, methanol and ethanol, dissolve inwater. Water evaporates, however not as fast as alcohol, therefore thecooling effect is not as noticeable. Water also is capable of hydratingcells.

2 Record three properties of water from the passage above.

• _________________________________________________

_________________________________________________

• _________________________________________________

_________________________________________________

• _________________________________________________

_________________________________________________

Check your answers.

The properties of solvents often determine their use. Some substancesyou commonly use contain these solvents.


Cosmetics and external medications

Almost all cosmetics and external medications such as creams, spraysand ointments contain one or more solvents.

1 Record any cosmetic products or medications you have used on yourskin over the last two weeks. This includes: deodorants, moisturisers,shaving cream, perfume, soap, after shave, ointment, rash or bitetreatments, burn treatments, heat rubs, disinfectants, nail polish, nailpolish remover and any others you can think of.

If you do not use many of these substances, you may question anotherperson.

_____________________________________________________

_____________________________________________________

_____________________________________________________

You may have found that you use more substances than you thought.In most cases, the substance would not exist without a solvent.

Water may also be referred to as aqua in an ingredients list. Alcohol canhave many names. The term ‘alcohol’ or ‘alcohol based’ in a list ofcosmetic ingredients usually refers to ethanol. The following list ofnames describe other forms of alcohol used:

• cetyl alcohol

• stearyl alcohol

• cetearyl alcohol (also called cetostearyl alcohol)

• denatured alcohol

• lanolin alcohol

• SD alcohol-A; SD alcohol 40

• methanol/methyl alcohol.

This list of alcohols does not totally cover the alcohols you are likely tofind in cosmetics and medications, however it is a guide.

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Some substances contain water and alcohol. You already know theproperties of water and alcohol. The water is often used as a skinhydrator as well as a solvent for acids, alkalis, salts and other polarsubstances.

In most cases, alcohol is present to dissolve non-polar substances such asoils. Once the alcohol has dissolved these substances, the alcohol may bedissolved in the water.

You may find it strange that oils should be present in cosmetics such asmoisturisers, however they play an important role. Oils not only replacenatural oils stripped by washing with soap and cleansers, they coat theskin surface, minimising the evaporation of water from the skin.

In other instances, alcohol may be present in such things as cleansers,and toners. Their function here uses the non-polar property to dissolveaway non-polar skin oils. However, skin cosmetics should not containgreater then the recommended 50% - 60% alcohol as it draws moistureout of the skin, having a drying effect. Water is also often present in thesubstances to help lathering and removal of oils and grime.

The non-polar nature of alcohol also dissolves non-polar molecules withodours used in perfumes and after shaves. Once applied to the skin, thealcohol evaporates, leaving a fragrant oil emitting an odour. This is lefton the skin, dissolved in non-ionic skin oils. These odours are quicklydestroyed through abrasion or excess heat.

Disinfectants and some cosmetics rely on relatively high concentrationsof alcohol to draw moisture out of skin micro-organisms, killing themand reducing the risk of infection.

Are you ready to investigate the cosmetics and skin medications in yourhome? If you don’t have many cosmetic products and externalmedications in your home, can you visit a supermarket, friend orneighbour?

Turn to Exercise 5.2 at the back of this part to investigate solvents used incosmetics and external medications



Subdermal implants

Some medications can be placed under the skin surface. The medicationis released over a period of time.

Turn to Appendix 2 on Controlled release drug delivery. Read the entireappendix then carry out the following activity.

1 The following diagrams demonstrate what is described in Appendix 2.Use the information in Appendix 2 to explain what is occurring in eachdiagram below.

Sta

ge Diagram of subdermal implant Explanation

1inner core with

hydrophobic film

outer core withhydrophilic film

2

3

4

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2 What substance dissolves the outer film, causing medication in theouter core to be released?

_____________________________________________________

3 Water alone will nor cause the inner film to degrade. What must bein contact with the inner membrane to cause it to weaken, enabling itto burst?

_____________________________________________________

4 Explain the function of subdermal implants currently used inhumans.

_____________________________________________________

_____________________________________________________

_____________________________________________________

Check your answers.

The solubility of medication taken orally determines the absorption ofdrugs. The nature of the digestive system determines the solubility andabsorption of drugs.

Turn to Exercise 5.3 at the back of this part to explain how body pHinfluences the solubility of medication in subdermal implants.



The digestive system

Are you able to identify parts of the digestive system? Can you recall theroles of the stomach and small intestine in the digestion of food? Thissection gives you opportunities to refresh your memory or learn about thedigestive system through fun activities.

Listen to the Digestive system section of the Skin audiotape/internet audiofiles to guide you through the following activities.

1 Label the parts of the human digestive system using the labels inAppendix 3.

The human digestive system.


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2 State the three food types.

_____________________________________________________

3 Use the Digestive system information in the Skin audiotape/internetaudio files to complete the table below.

Organ Role in digestion

stomach

duodenum

gall bladder

pancreas

small intestine


4 Explain why the stomach and the small intestine have different pHvalues.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

5 In general terms, explain the role of the stomach in breaking downfood.

______________________________________________________

______________________________________________________

______________________________________________________

6 In general terms, explain the role of the small intestine in breakingdown food.

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

______________________________________________________

Check your answers.

The substances you consume must become soluble through digestion tobe absorbed by the body and used for energy. How soluble a substanceis determines the rate at which it is absorbed by the body.

Turn to Exercise 5.4 at the back of this part to label and state the functionsof parts of the human digestive system.


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Summary

Below is a list of the contents for Part 5. Write three things you learntunderneath each heading title. Keep your answers brief as they are theyare to represent key concepts only.


_________________________________________________________

_________________________________________________________

_________________________________________________________

Alcohol as a solvent

_________________________________________________________

_________________________________________________________

_________________________________________________________

Solvent properties

_________________________________________________________

_________________________________________________________

_________________________________________________________

Cosmetics and external medications

_________________________________________________________

_________________________________________________________

_________________________________________________________


Subdermal implants

_________________________________________________________

_________________________________________________________

_________________________________________________________

The digestive system

_________________________________________________________

_________________________________________________________

_________________________________________________________


Record five things you need to do in the next week for your open-endedinvestigation.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

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Appendix 1

water water sugar

water water sugar

water water sugar

water water sugar


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Appendix 2

Controlled release drug delivery

Subdermal implants in animals

An implant placed under the skin surface contains a compressed core andtwo layers of film coating. The outer film is compatible with skin tissueand degrades at a set rate when in contact with water from the body. Thedissolution of the outer membrane releases medication between the firstand second layers of film.

The inner core, protected by the hydrophobic film begins to swell as theouter film degrades. The inner film is hydrophobic but dissolves at bodypH. Non-polar molecules inside the film become polar when in contactwith body pH. The polar molecules are then more able to dissolve inbody water. The swelling of the inner core, combined with thedissolving of the inner film causes the inner film to rupture twenty one tosixty days after implantation. In this way, the core medication is releasedin a pulse. The medication is then able to travel through the bloodstreamto target cells.

The overall effect is similar to two injections of a drug with only oneveterinarian bill.

The above information has been adapted from:

Theil, W J. Panagiotidis, J. Controlled Release Drug Delivery,<http://www.vcp.monash.edu.au/pharmaceutics/res-control.html>(accessed 17 June 2000)

Subdermal implants in humans

Subdermal implants are currently being used to deliver steady doses ofhormones in females, replacing the contraceptive pill. Such implants areeffective for up to five years.


The slow release of drugs work on similar principles to those outlinedabove, however the chemistry behind the slow release of drugs is morecomplicated.

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Appendix 3

Cut out the following labels for the human digestive system.

small intestine

stomach

liver

oesophagus

large intestine

duodenum

gall bladder

rectum

pancreas

mouth


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Suggested answers

Solvents1 Solvents are substances that will dissolve a solute.

2 a) water

b) alcohol


1

HO

H

2

HO

H

3

4

sugarsugar

sugarsugar


5 Water is a solvent in cordial, tea with sugar, disinfectants andswimming pools. (Other answers are acceptable.)

Alcohol as a solvent1

H C

H

H

C

H

H

OH slightly polarnon-polar

2 The polar end can dissolve in water and the non-polar end candissolve in oil.

Larger alcohol moleculesAlcohol is used as a solvent in methylated spirits, enamel paints,after shave and perfumes. (Other answers are acceptable.)

Solvent properties1 • Alcohol evaporates quickly, having a cooling effect.

• Alcohol is able to dehydrate living cells, killing them.

• Some alcohols may be used as surfactants or emulsifiers due tothe polar and non-polar ends of the molecules.

2 • Water is able to dissolve polar substances due to the polar natureof water molecules. This includes acids, alkalis and somealcohols.

• Water is able to hydrate cells

• Water evaporates causing a mild cooling effect.

Subdermal implants

1 Stage Explanation

1 The subdermal implant contains an inner core and outer core.The inner core is protected by a hydrophobic film and the outer coreis surrounded by a hydrophilic film

2 The outer film dissolves in body water, releasing medication to thebody. The inner core remains protected by the hydrophobic film.

3 As the outer core degrades, water moves into the inner core,causing it to swell.

4 The inner core eventually ruptures, releasing a pulse of medicationto the body 21 to 60 days after initial implantation.

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2 Water dissolves the outer film, causing medication in the outer coreto be released into the body.

3 The inner core must be in contact with body pH for it to degrade,allowing it to weaken and burst.

4 Subdermal implants are currently used in humans replacing thecontraceptive pill. The implants can protect females againstpregnancy for up to five years.

The digestive system1

liver

pancreas

gall bladder

duodenum

rectum

mouth

oesophagus

small intestine

large intestine

stomach

2 The three food types are carbohydrates, protein and fats.

3 Organ Role in digestion

stomach begins digestion of protein and churns food into apaste; protease enzymes digest protein; the protein isbroken down into peptides; hydrochloric acid helps theenzymes present to function and kills microbes.

duodenum receives contents of stomach, bile from the gallbladder and enzymes from the pancreas; thedigestion of fat which has been broken up into smallerglobules commences; acidic stomach contents areneutralized so that ph rises to between 6 and 8

gall bladder secretes bile into the duodenum; bile breaks oilglobules into smaller globules; bile also neutralisesstomach acids, causing the food to become morealkaline


pancreas enzymes further break down protein, carbohydrateand starch which are more able to function in thehigher pH conditions

small intestine the small intestine produces a fluid containingenzymes to complete digestion of carbohydrates,protein and fats; peptidase enzymes break downproteins; lipase enzymes further digest fat; lactasebreaks down milk sugar (lactose) and other enzymesbreak down other carbohydrates

carbohydrates have become glucose; proteins havebecome amino acids and fats have become fatty acidsand glycerol; these are absorbed across the smallintestine wall into the bloodstream

4 The stomach and the small intestine have different pH values asdifferent enzymes function best in differing levels of acidity andalkalinity eg. pepsin functions best in the stomach at a pH of 1 to 2while other enzymes such as protease and lipase function best in apH range of 6 to 8.

5 The stomach churns food into a paste and begins to break downproteins into peptides with protease enzymes.

6 The small intestine contains a mixture of enzymes from the gallbladder, pancreas and small intestine. Bile breaks down fats intosmall globules. Pancreatic juices and juices secreted from smallintestine walls digest proteins, carbohydrates and fats with enzymes.Once soluble, the digested food may be absorbed into thebloodstream.

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Exercises - Part 5


Exercise 5.1

The diagram below shows a shaded polar substance (solute) dissolved inanother polar substance (solvent).

1 Is the unshaded solvent in the above diagram water or alcohol?Explain your answer.

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________


2 The diagram below shows water, oil and alcohol molecules.

a) Identify the water, oil and alcohol molecules in the legendbelow.

b) Outline your reasons for molecule identification in the legend.

Legend

molecule water/alcohol/oil reason

c) Explain what is happening in the above diagram using thewords: polar, non-polar, solvent; emulsion; alcohol; water; andoil. You may use more than one sentence.

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

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Exercise 5.2

Collect six cosmetics and/or external medications from the following list:

• deodorants

• moisturisers

• shaving cream

• perfume

• after shave

• nail polish

• nail polish remover

• ointment

• rash or bite treatments

• burn treatments

• heat rubs

• disinfectants

• vapour rubs

• disinfectants.

Only choose products with ingredients listed on them. Some substancesmay list the active ingredient only and are not recommended for yourinvestigation unless the active ingredient is a form of alcohol. Choose atleast one product that contains no alcohol.

Look at the list of ingredients on the package. Place a tick in the relevantbox to indicate the solvents present. If alcohol is present, place a tick inthe alcohol column. Remember, there are many names for alcohol listedon page 12. Other alcohols may be present other then those indicatedearlier. If water (aqua) is present, place a tick in the water column.

The first one has been done for you as a guide.

Su

bst

ance

Ext

ern

alm

edic

atio

n

Co

smet

ic

Alc

oh

ol

pre

sen

t

Wat

erp

rese

nt

Lux® awaken moisturiser


1 a) List the cosmetics and medications containing water only.

__________________________________________________

b) Place a small amount of one of those substances on your skin.Describe how it feels eg. cold, warm, oily, slimy.

__________________________________________________

__________________________________________________

__________________________________________________

2 a) List the cosmetics and medications containing alcohol only.

__________________________________________________

b) Place a small amount of one of those substances on your skin.Describe how it feels.

__________________________________________________

__________________________________________________

__________________________________________________

c) Use the information on the properties of alcohol on page 11 toexplain why the substance containing alcohol feels like it does.

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

3 a) List the cosmetics and medications containing alcohol andwater.

__________________________________________________

b) Use the information on page 10 to explain why these substancescontain alcohol and water.

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

__________________________________________________

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Exercise 5.3

Explain how subdermal implants rely on body pH to deliver medicationto body tissue. You may use diagrams in the space provided below tohelp with your explanation.

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________



Exercise 5.41 Label the parts of the digestive system identified with a line on the

diagram below.

2 Fill out the functions in digestion of those parts indicated with a box.Include as much detail as possible. Show variations in pH.

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Lifestyle chemistry

Part 6: Good medicine


AMENDMENTS


Lifestyle Chemistry


• Mixing it up

• Your skin


• Dissolve it!

• Good medicine


Information Systems

Option

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Part 6: Good medicine 1

Contents

Introduction ............................................................................... 2

Drug solubility............................................................................ 3

Addictive narcotics ...............................................................................4

Vitamins ................................................................................................5

Tablets ..................................................................................................6

Investigating the rate at which different drug forms dissolve .............8

Drug administration ............................................................................11

Drug action on the body.....................................................................12

Summary................................................................................. 13

Appendix 1 .............................................................................. 15

Appendix 2 .............................................................................. 17

Appendix 3 .............................................................................. 19


Exercises – Part 6 ................................................................... 25

Bibliography ............................................................................ 39


Introduction

Medications can be administered to the body in many different ways.The choice of administration can depend on the solubility of the drug.How a drug acts on the body is also closely related to its solubility.You will learn the differences between common forms of oral medicationand appreciate why water-soluble vitamins need to be a more regular partof your diet than fat-soluble vitamins.


• account for the absorption of a drug and its action on/in the body interms of its solubility

• explain why a knowledge of the solubility of materials can be usedto design drugs for specific tasks

• identify that the manner of administration of a drug may be related toits solubility

• identify vitamins that are water-soluble and those that are fat-soluble.


• perform an investigation to gather data comparing the rate at whichcapsules, tablets, enteric coated tablets and slow-release tabletsdissolve

• gather, process and analyse information from first-hand or secondarysources to relate the significance of solubility of a medication to itsaction on/in the body.


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Drug solubility

Have you ever taken medication that made you feel drowsy? Have youheard of medication that won’t make you drowsy? Drug companiesdesign their drugs to cause specific reactions such as relief from coldsand flus. How the drug acts on the body and the effects it causes is oftendetermined by the solubility of the drug.

You know that non-polar substances will dissolve in fats and polarsubstances will dissolve in water.

Nerves in the brain are insulated with myelin which is made up of 80%fat. Body cells are also surrounded by membranes containing fats.

Nerves throughout the body send messages across gaps between theirconnecting nerve fibres. The signal between nerve fibres is transferredby the movement of small polar molecules with positively chargednitrogen atoms. The blood and lymph that circulates throughout thebody is mostly water and so readily carry water soluble polar substances.

Although the movement of messages across the gap from one nerve fibreto the next involves polar molecules, some non-polar drugs can affecttransmission of nerve messages. Certain non-polar drugs coat the ends ofnerve fibres and slow or stop messages from getting through.

1 Circle the correct word in the following sentences based on the aboveinformation.

a) A polar/non-polar drug will be absorbed more readily into braincells through fatty membranes.

b) A polar/non-polar drug could affect connections between nerves inthe body


2 Reconstruct the following sentences.

a) diffuse Non-polar drugs brain membranes cell will across easily.

b) drowsiness The cause may drugs.

_________________________________________________


It is clear that a knowledge of drug solubility is essential for designingdrugs for specific tasks in the body. This is demonstrated by comparingaddictive narcotic drugs.

Addictive narcotics

Narcotics are drugs that produce general anesthesia (narcosis) of thebody. Whether drowsiness or unconsciousness or death occur dependson the quantity, quality and extent of any previous intake of the drug.

Opium is a juice obtained from unripeseeds of the oriental poppy plant. About10% of the mass of opium is morphine.Morphine injections are used to relieveextreme pain in injuries and terminalcancer patients. The morphine is carriedthroughout the body in the blood and canpass across the blood-brain barrier andaffect the brain. Morphine can relievepain from nerves at the site of an injuryas well as dull the pain receptors in thebrain.

OHO OH

CH3

N

Morphine – the OH groups andN atom make it polar enough todissolve in blood

Heroin is diacetyl morphine. Heroin is aless polar molecule called an ester madeby reacting morphine, an alcohol, withacetic acid. Because heroin is less polarthan morphine it passes through the fatlayers of the brain more quickly. Heroinhas similar effects on the human body tomorphine but produces a strongeraddiction, more difficult to cure.

OOCH3C

O

O CCH3

O

CH3

N

Heroin (diacetyl morphine) –less polar than morphine sopasses through fat layers of thebrain more quickly

Whereas morphine is a natural productand heroin a slightly modified naturalproduct made by reacting morphine withacetic acid, methadone is synthesisedfrom simpler chemicals. The syntheticnarcotic methadone is used to cureheroin addiction. It is addictive likeheroin but does not produce a stupor likeheroin.

CH3

N

CH CH3

CH3

C CH2CH3

O

Methadone – a syntheticproduct made from chemicalsderived from petroleum

A person undergoing methadone treatment for heroin addiction is betterable to cope with work but it still an addict, possibly for life.

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The Centre for Green Chemistry at Monash University in Victoria isdoing research on producing non-addictive forms of morphine. Researchworkers are adding highly polar groups containing N atoms to morphine.These highly polar forms of morphine will stay in the blood and relievepain at the site of injury. The highly polar molecules are not able topenetrate the fatty barriers between the blood and brain. It is hoped thatthe patient will remain conscious as their brain is unaffected and theywill be relieved of pain coming from the site of injury.

Vitamins

How vitamins are absorbed and stored in the body is also dependant onsolubility.

Vitamins B and C are water-soluble and can easily ‘stick’ to watermolecules in the blood and be circulated to where they are needed in thebody. The polar nature of these vitamins however, also causes them tobe easily removed from the body in urine. These vitamins therefore needto be consumed regularly, preferably each day.

Vitamins A, D, E and K are fat-soluble and can easily be absorbed intocells through cell membranes. This can cause them to accumulate insidecells. If too many of these vitamins accumulate in the body as a result oftaking too many vitamin supplements they can have a toxic effect. Thesefat-soluble vitamins do not have to be consumed every day in a balanceddiet but should be part of the diet each week.

Many homes have at least one bottle of vitamins. Look for a bottle ofvitamins at home. If you don’t have any, again, ask a friend or neighbour.

Aim to find a multivitamin container, however any vitamins are fine such asvitamin B complex.

1 Place a tick in the column below if your vitamin container indicatesany of the following vitamins.

Vitamin Present in vitamin sample

A

B

C

D

E

K


2 Write the instructions for adult use eg. ‘Take three times daily withfood.’

______________________________________________________

______________________________________________________

With your knowledge of water-soluble and fat-soluble vitamins, explainwhy the dose must be taken as instructed. Outline the risks if not taken asinstructed.

_____________________________________________________

_____________________________________________________

_____________________________________________________

_____________________________________________________

Check your answers.


Tablets

Tablets can come in many shapes, sizes and colours, with and withoutcoatings. Capsules are another form of oral medication.

Use the space below to draw the shapes of four different tablets you haveseen eg. Disprin®, Asprin®, cold and flu tablets and vitamins.

1 Appendix 1 contains information about the solubility of tablets,capsules, enteric coated tablets and slow-release tablets. Use theinformation in Appendix 1 to fill in the following table.

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Tablet Activity in the stomach Activity in the small intestine

tablet

entericcoated tablet

capsule

slow-releasetablet

Check your answers.

2 Write two exam type questions and their answers on the solubility ofdifferent types of tablets from the information in Appendix 1.

a)

_________________________________________________

_________________________________________________

_________________________________________________

b)

_________________________________________________

_________________________________________________

_________________________________________________

Turn to Exercise 6.1 at the back of this part to demonstrate yourunderstanding of the solubility of different tablets.



Investigating the rate at whichdifferent drug forms dissolve

Aim

To compare the rate at which a variety of drug forms – capsules, tablets,enteric coated tablets, and slow-release tablets – dissolve.

Apparatus

You will need to obtain a variety of drug forms such as:

• capsules (these usually have a cylindrical shape with rounded ends,the capsule is made of a hard jelly like material; do not get capsuletswhich are tablets in the shape of a capsule)

• tablets (typically hard, disc shaped)

• enteric coated tablets (coated with a plastic looking material)

• slow-release tablets (sometimes marked 12 hour or some other timerelease)

Ideally they should be different forms of the same drug, containing aboutthe same amount of drug in each. However it is extremely unlikely youwill be able to find the same drug in the four drug forms listed. Aspirinand paracetamol are two pain relief drugs that come in a variety of formsbut you may find it difficult to find more than three forms at a localsupermarket or pharmacy. You may be better off looking to see whatold, unwanted medications you have at home in the form of capsule,tablet, enteric coated tablet and slow-release tablet.

Some changes should be observed in the first few minutes, other changeswithin an hour. The last observations could be made after 24 hours.

• You will also need a number of identical transparent containers tohold liquid and the drug forms.

• The liquid used to test solubility could be just water. Acidconditions (as in the stomach) could be investigated by using vinegar(about 5% acetic acid). Alkaline conditions (as in the smallintestine) could be investigated by using about 5% solutions of eithersodium bicarbonate (bicarb of soda) or sodium carbonate (washingsoda).

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Temperature of the solutions could be room temperature or could be keptcloser to human body temperature by placing containers in a warm place(away from the reach of animals and children).

Method

When you have at least three of the four drug forms, set up yourequipment with suitable labelling, away from the reach of animals andchildren.

• Aim for valid (effective) results and reliable (trustworthy) data.

• Modify procedures as needed and analyse the effect of thesemodifications.

• Repeat trials of experiments where appropriate.

• If you investigate variables such as the acidity/alkalinity of thesolution make sure that you use a control such as water.

• Where possible record quantitative, rather than qualitative, data.

If you cannot observe any change in the drug forms after a reasonabletime try stirring each container in the same way for the same amount oftime. This simulates what happens in the human stomach and smallintestine where muscular walls move to mix the contents.

If you are carrying out the activity in low room temperatures and notobserving much change transfer the apparatus to a warmer place. Mostchemical processes proceed faster at higher temperatures.

Results

Record these in a table.


Conclusions

If you wish to see a HSC question based upon having done thisactivity and to see the responses given by HSC candidates then usethe NSW HSC 2001 standards package CD-ROM 15340 for SeniorScience.

Refer to question 17 (6 marks) about assessing the validity ofconclusions drawn from this investigation. The three Band 5/6responses provided for this question will show you what is requiredfor full, or close to full, marks.

If you do not have access to this standards package contact yourteacher for help.

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Drug administration

Have you ever had a needle? Did it hurt? Would you rather have taken atablet? Some drugs cannot be administered orally because they will bedestroyed be acids and enzymes in the digestive system or the drugmolecules are too large to be absorbed through the lining in the smallintestine. Tablets and injections are only two forms of medication.

Can you think of any other forms of medication? (You studied two of themin the last part.)

_________________________________________________________

_________________________________________________________

Appendix 2 explains the use of different forms of medication. Read thisinformation, then carry out the following activity.

Use the information in Appendix 2 on Drug administration to answer thefollowing true/false questions. Write a ‘T’ or ‘F’ in the space next to eachstatement.

1 Drugs can be administered orally.

2 The manner of drug administration can depend on the speed ofrelief required.

3 Asthma medication in most commonly injected.

4 Medication cannot be administered through the skin.

5 Medication required to circulate around the body needs to bepolar.

6 Anaesthetic must be polar to remain inside localised cells.

7 The same drug may be administered in more than one way.

8 The nature of target cells is not important in the designing ofdrugs.

9 Drugs in nasal sprays often circulate around the body onceadministered.

10 Insulin is non-polar.

Check your answers.

Drugs that are injected often need to act on the body quickly and areneeded in a particular part of the body. Sometimes these medicationscannot be absorbed through the skin, stomach, nasal passages or lungs.


Oral medications can be self administered and absorbed through thedigestive system.

Medications that use inhalers often work on the tissue immediately,remaining in lung cells. Nasal sprays focus drugs in the cells in nasalpassages, also acting quickly.

Dermal patches are easy to use. They can concentrate their medication ina particular area or administer soluble drugs to flow around the body.

You should understand from the information you just gathered that ifmedication is to be absorbed into cells in the body through membranesmade of fats, the drugs must be fat-soluble. Do polar or non-polarsubstances dissolve in fats? If you are unable to answer that question,you should look up the answer in Part 4 now.

If medication is to be circulated around the body with the blood, it mustbe water-soluble. Do polar or non-polar substances dissolve in water?Again, if you cannot answer this question, find the answer in Part 4.

It is essential you understand the difference between fat-soluble andwater-soluble substances and their relationship between non-polar andpolar substances for you to understand the next section. If you are notsure, revise Part 4 or contact your teacher for help.

Drug action on the body

Appendix 3 contains information on four different drugs used externally.There are six essential points you need to know before gatheringinformation from Appendix 3 and carrying out Exercise 6.2.

• polar substances will dissolve in water

• non-polar substances will dissolve in fats

• cells are surrounded by membranes made up of fats

• blood flows through the body as a water based mixture

• alcohol has polar and non-polar ends

• water is polar

Miscible means ‘mixing’. Miscible substances such as ethanol C2H5OHand water HOH mix freely with one another. A drug which is difficult todissolve in water can be dissolved in ethanol first and then water added.This produces an alcohol based solution of the drug in aqueous alcohol.

Turn to Exercise 6.2 at the back of this part to relate the significance ofmedication solubility and its action on the body.

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Summary

Complete the sample test in Exercise 6.3 to gauge your progress in Lifestylechemistry.


Complete your open-ended investigation report in Exercise 6.4 at the back ofthis part unless your teacher has specified a different date for its submission.


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Appendix 1

Tablets, capsules, enteric coated tabletsand slow-release tablets

Tablets are typically broken down in the stomach. Some of the drug isabsorbed in the stomach, however, most is absorbed through the smallintestine. A spherical tablet has less surface area per volume than a discshaped tablet. Therefore, the shape of the tablet affects the rate of drugdissolution and absorption.

Many drugs are destroyed in the low pH of stomach acid. Some drugscan irritate or damage the tissue in the oesophagus or stomach.Capsules and enteric coated tablets are designed to overcome suchproblems. The coating surrounding each is not affected by strong acid.This protects the drugs until they pass into the small intestine. Here, thepH is at 6 – 8. Capsule and enteric coatings begin to dissolve here,releasing the drugs within. This prevents the drug from irritating thestomach and possibly causing bleeding. Capsule and enteric coatingsdissolve at different rates, therefore releasing their drugs at different rateswhile in the small intestine.

Slow-release tablets often contain two or more films. The outer filmprotects the outer core medication. The inner film protects the inner coremedication. As the outer film gradually dissolves, the outer coremedication is gradually released. Once almost all the outer coremedication is released, the inner film dissolves, gradually releasingmedication. Refer to the diagram below.

outer film inner film

outer core(containingmedication)

inner core(containingmedication)

outer core medicationis released as outerfilm dissolves

inner film dissolves,releasing medicationafter the outer corehas dissolved

The action of a slow-release tablet as it travels through the small intestine.


Different slow-release tablets release their medication in different wayshowever, slow-release tablets are generally taken once daily. One slow-release tablet can release medication for as long as it remains in theintestine.

Medication is absorbed into the body as a result of diffusion. Theconcentration of a drug in the small intestine must be greater than that inthe body for the drug to be absorbed. For this reason, a great deal ofdrugs taken orally are lost as waste.

Glossary of some solid dosage medication forms

If you look at a range of medications you will find that thepharmaceutical industry has been creative in making up new words todescribe its products:

cap abbreviation for capsule

caplet tablet of capsule shape

capseal gelatin coated tablet of capsule shape

capsule cylinder shape with rounded ends, usually madeof gelatin and in two parts that can be opened

dispersable tablet tablet containing soluble solid acid and acarbonate that react with water breaking thetablet apart as it efffervesces

effervescent tablet same as dispersable tablet defined above

enteric coating that is stomach acid resistant butsoluble in the alkaline small intestine

gelcap gelatin coated tablet

meltlet melt in mouth tablet

minicap gelatin coated tablet or small capsule

slow-release designed to provide slow release over time

tab abbreviation for tablet

tabsule capsule shaped tablet

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Appendix 2

Drug administration

Some medications are required to circulate around the body such asantibiotics and insulin. There would be little use in taking antibiotics foran infected cut in your foot if the antibiotics were not soluble enough toget from your digestive system to your foot. Other medications are moreuseful in specific cells.

Asthma medication often needs to remain in lung cells. Anaesthetic isrequired to numb pain sensors in a specific area of the body.Dermal patches for warts aim to deliver their medication to a localisedwart on the skin. Drugs present in nasal sprays generally remain in nasalcells to minimise the build up of mucus.

There are two main rules for the designing of drugs.

• If the drug is to enter cells and remain there, it must be non-polar(or fat soluble) in order to cross the cell membrane then becomepolar once inside the cell. A nitrogen atom in a drug can attract apositive hydrogen ion and change the drug from slightly polar topolar.

• If the drug is to circulate around the body, it must be polar to becarried by water in the blood.

Take a look at the medications discussed: antibiotics, insulin, asthmamedication, anaesthetic, wart patches and nasal sprays.The administration techniques used for these drugs differ greatly.

Drugs may be administered orally, through the digestive system; injectedinto the bloodstream or muscle; inhaled into the respiratory system;absorbed through the skin; or absorbed through the nasal passages.The manner of administration is dependant on four key elements.

• the speed of relief required

• the target cells and the ease of access

• the solubility of the drug


• ease of administration.

Insulin is destroyed in the digestive system. For this reason it is injectedinto the bloodstream where it can take immediate action. Ventolin® andother asthma medications are inhaled to access the lung cells directly andoffer fast relief. Nasal sprays work in a similar way, remaining in nasalcells. Antibiotics may be injected, however they are most commonlytaken orally for self administration purposes. Dermal patches can beused to act on local skin cells only and can be easily administered.

The manner of drug administration is therefore clearly dependant on:

• the action required on the body


• ease of administration

• the speed of delivery.

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Appendix 3

The information below has been sourced from:Orion Laboratories Pty Ltd., Western Australia. Material safety data sheets,<http://www.orion.net.au/> (accessed 4 July 2000).

Surgical spiritUSES For drying and astringent action on the skin or as a solvent.

PHYSICAL PROPERTIES

Description: Clear, colourless, spiritous liquid with an odour of MethylSalicylate.

Solubility in Water: Miscible

INGREDIENTS

Chemical Entity Proportion

Methyl salicylate

Diethyl phthalate

Castor Oil

Methylated Spirit

<10%

<10%

<10%

to 100%

PRECAUTIONS FOR USE

PERSONALPROTECTION

Avoid eye contact. If spillage or splashing are likely to occurduring handling, wear safety spectacles. Approved barriercreams may prove useful in preventing dermatitis whenprolonged skin contact is unavoidable.


Benzoin compound tincture B.P.C.USES Benzoin Compound Tincture is used mainly as an inhalation

(5 mL to 500 mL of hot water) in bronchitis and acutelaryngitis. It may be applied undiluted as an antiseptic andstyptic to small cuts and to intact skin as a protectivedressing under occlusive plasters and bandages.

PHYSICAL PROPERTIES

Description: A dark brown alcoholic liquid.


Pack Size: 50 mL

INGREDIENTS


Ethanol (alcohol)

Benzoin

Prepared Storax

Tolu Balsam

Aloes

Water

>70%

10%

7.5%

2.5%

2%

<10%

PRECAUTIONS FOR USE

PERSONALPROTECTION

Avoid eye contact. If spillage or splashing are likely to occurduring handling, wear safety spectacles. Approved barriercreams may prove useful in preventing dermatitis whenprolonged skin contact is unavoidable.

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Brilliant green and crystal violet paint B.P.USES Marking of skin prior to surgical procedures.

PHYSICAL PROPERTIES

Description A dark coloured solution with an alcoholic odour.

Solubility in Water Miscible

pH Not known

Pack Size 25 mL

INGREDIENTS


Ethanol

Brilliant Green

Crystal Violet

Water

42 - 48%

0.5%

0.5%

To 100%

PRECAUTIONS FOR USE

PERSONALPROTECTION

Avoid eye contact. If spillage or splashing are likely to occurduring handling, wear safety spectacles. Gloves and protectiveclothing may be worn as the product stains skin and clothing.


GluticolUSES As a test dose for Glucose Tolerance Testing in cases of

suspected glucose intolerance for Diabetes Mellitus, or as acalorific supplement.

PHYSICAL PROPERTIES

Description: An orange liquid with a characteristic orange odour.


pH: 1.5 - 3.5

INGREDIENTS


Glucose Anhydrous B.P.

Citric Acid Anhydrous B.P.

Methyl Hydroxybenzoate B.P.

Benzoic Acid B.P.

Colour

Flavour

Water Purified

30 -60%

< 10%

< 10%

< 10%

< 10%

< 10%

to 100%

PRECAUTIONS FOR USE

PERSONALPROTECTION

Personal protection is not necessary. Spillage will be sticky andmay stain clothing.

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Suggested answers

Drug solubility1 a) A non-polar drug will be absorbed more readily into brain cells

through fatty membranes.

b) Either answer could be correct:A polar drug could affect connections between nerves fibres if itinterfered with the movement of small polar molecules

A non-polar drug could affect connections between nerves inthe body by coating the ends of the nerve fibres.

2 a) Non-polar drugs will diffuse across brain cell membranes easily.

b) The drugs may cause drowsiness.

VitaminsVitamins should be often taken with food and liquid to increase theirsolubility for absorption. If too many vitamins are taken, it can have apoisonous effect on the body. Other answers are acceptable.

Tablets

Tablet Activity in thestomach

Activity in the small intestine

tablet the drug dissolvesand some isabsorbed

absorption

entericcoatedtablet

drug is protectedby enteric coating

enteric coating dissolves; the drug then dissolvesand is absorbed

capsule drug is protectedby capsule coating

capsule coating dissolves; the drug thendissolves and is absorbed

slow-releasetablet

drug is protectedby film coating

outer coating slowly dissolves, releasing outerlayer of medication; inner film then dissolves,releasing inner core medication for absorption


Drug administrationT 1 Drugs can be administered orally.

T 2 The manner of drug administration can depend on the speed ofrelief required.

F 3 Asthma medication in most commonly injected.

F 4 Medication cannot be administered through the skin.

T 5 Medication required to circulate around the body needs to bepolar.

F 6 Anaesthetic must be polar to remain inside localised cells.

T 7 The same drug may be administered in more than one way.

F 8 The nature of target cells is not important in the designing ofdrugs.

F 9 Drugs in nasal sprays often circulate around the body onceadministered.

F 10 Insulin is non-polar.

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Exercises - Part 6


Exercise 6.1

Imagine you are a senior chemist in a leading drug company.The research scientists in your firm have discovered a drug that willtarget and destroy cancer cells in patients. They need a simple way ofadministering the drug. They come to you for advice concerning oraladministration of the drug through tablets, capsules, enteric coated tabletsor slow release tablets.

You look at the structure of the drug. It could easily be destroyed instomach acid.

1 What three options for oral medication do you have knowing thedrug would be destroyed in the stomach? Explain your answer.

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2 You test the drug. It is non-polar. What does this tell you about thedrug and why is this important?

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3 The structure of the drug is similar to other medicines which cancause irritation in the small intestine. You know that the drug mustbe released slowly throughout the small intestine to minimiseirritation. What form of oral administration do you suggest for thisdrug and why?

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4 Because the drug is non-polar, you know the drug will not beadequately absorbed without some fats present. What would happenif the drug was taken on an empty stomach and why?

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5 What would you suggest be put on the label under in the ‘directionsfor use’ to overcome this problem? Explain your answer.

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Exercise 6.21 Draw up a table in pencil with six columns and five rows. You may

choose to draw a draft table first before recording your final versionon the following page.

2 Write these headings in each column from left to right: medication;contains alcohol; contains water; water-soluble; fat-soluble; and willcross cell membranes. You should now have all the headings filledin.

3 The titles for each of the four remaining rows are: benzoincompound tincture B.P.C.; brilliant green and crystal violet paintB.P.; gluticol; and surgical spirit. Write these names in the far leftcolumn. These names match the medications in Appendix 3.

Your table should now have labels across the top and down the left side.

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4 Use the data in Appendix 3 to place ticks or crosses in the relevantcolumns eg. Surgical spirit contains alcohol and no water – place atick in the contains alcohol column and a cross in the contains watercolumn. Note that the names of alcohols usually end in –ol.

You will need to draw your own conclusions whether the drug willcross cell membranes based on ingredient and solubility information.

5 After you have completed the table, create an appropriate title for thetable. Write this above the table then underline it.


Use the information in the table to answer the questions on the followingpage.

6 Which medication(s) will be absorbed by body cells? Explain why.

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7 Which medication(s) will not be easily absorbed by cells in thebody? Explain why.

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8 Some of the drugs outlined in Appendix 3 contain both water andalcohol. Identify these drugs.

9 If drugs are transported through the blood to target cells in the body,explain why is it important the drugs have non-polar and polarcharacteristics.

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Exercise 6.3

Complete the following practice test to gauge your progress in Lifestylechemistry.

Multiple choice questions (worth one mark each)

1 A colloid is a mixture that:

(A) leaves no residue when filtered

(B) a beam of light cannot be seen in

(C) contains particles smaller than 10-6 mm in diameter

(D) contains solids which settle out over time.

2 Some insect are able to walk on water because:

(A) water molecules have strong adhesive forces

(B) water molecules contain hydrogen and oxygen atoms

(C) water molecules have strong cohesive forces

(D) insects are not able to walk on water.

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3 Oil is immiscible in water unless an emulsifier is added.The emulsifier holds oil globules in the water by:

(A) separating oil globules

(B) repelling other emulsifiers with the same charge

(C) surrounding oil globules

(D) all of the above.

4 Salad dressing made with half a cup of oil, a quarter of a cup oflemon juice and a teaspoon of sugar is a colloid. Which of thefollowing colloid types best describes this colloid?

(A) oil-in-water colloid

(B) solid-in-liquid colloid

(C) water-in-oil colloid

(D) gas-in-liquid colloid

5 A solvent:

(A) is the liquid a solute dissolves in

(B) may be polar or non-polar

(C) may be water or alcohol


6 Which of the following statements is not true?

(A) tablets without coatings mainly dissolve in the small intestine

(B) medication in enteric coated tablets is absorbed in the small intestine

(C) medication in capsules is protected while in stomach acid

(D) slow release tablets release their medication throughout theintestines.

7

The diagram above could represent:

(A) a surfactant

(B) an emulsifier

(C) an alcohol molecule



8 Identify the parts of the digestive system labeled with the lettersW, X and Y respectively.

wx

y

(A) oesophagus, stomach, small intestine

(B) stomach, gall bladder, pancreas

(C) liver, stomach, large intestine

(D) stomach, pancreas, liver

9 Vitamins A, B and C are respectively:

(A) water-soluble; fat-soluble; water-soluble

(B) water-soluble; water-soluble; fat-soluble

(C) fat-soluble; water-soluble; fat-soluble

(D) fat-soluble; water-soluble; water-soluble.

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10 The method used for drug administration depends on:

• the speed of relief required

• the target cells and the ease of access


• ease of administration.

A doctor gives a patient who is suffering an acute asthma attack aninjection of cortisone. Which of the four factors above is most importantin deciding the method of drug administration in this case?

(A) the speed of relief required

(B) the target cells and the ease of access

(C) the solubility of the drug

(D) ease of administration

Short answer questions (worth three marks each)

11 Briefly explain why water drops are spherical in shape.

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12 a) Explain the role of the acid mantle on human skin.

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b) Explain why skin and hair products must be compatible withskin pH.

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13 Two common solvent are water and alcohol. List three properties ofeach that make them useful in cosmetics.

a) water

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b) alcohol

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14 a) Give three examples of gas-in-liquid colloids.

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b) You made some mixtures which were either suspensions orcolloids during this topic. Choose one of these and brieflyoutline how it was made.

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15 Explain why the solubility of a drug is important in designing a drugfor a specific task.

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16 a) Shower gels, soaps and shampoos contain some similaringredients. Explain the main functions of shower gels, soapsand shampoos.

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b) Define the term biodegradable and indicate the difference in thebiodegradability of soaps and detergents used today.

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17

a) What pH value does the stomach have?

b) What pH value does the small intestine have?

c) Explain why the difference in acidity between the stomach andthe small intestine is important in the digestion of food.

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18 Explain the role of the following organs in the digestion of food.

liver

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gall bladder

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pancreas

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19 The diagrams on the right show the stages of medication releasefrom a subdermal implant. Next to each diagram briefly explainwhat is occurring in each stage.

a) __________________________

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b) __________________________

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c) __________________________

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Extended answer questions (worth five marks each)

20 a) Underarm skin has different conditions to skin on the arm.Explain the different conditions on these parts of the body.

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b) Is the pH of skin in underarms more or less acidic than skin pHon the arm?

c) The relationship between the pH, nutrients present, moistureavailability and the microflora present on under arm skin is acontroversial one. Discuss the various ideas on the relationshipthat is thought to exist between the microflora found in underarm skin, the skin pH and the conditions that exist there.

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21 Species of microflora Part of body found

Staphylococcus epidermidis

Staphylococcus hominis

Micrococcus luteus

Corynebacterium jeikeium

Propionibacterium acnes

Propionibacterium avidum

Propionibacterium granulosum

Brevibacterium epidermidis

Acinetobacter calcoaceticus

Malassezia furfur

Trichophyton mentagrophytes

Demodex folliculorum

upper body and face

legs and arms

head, legs and arms

armpit

face and shoulders

armpit

side of nose

in between toes

groin and front of elbow

scalp, ear and back

feet

face

a) Use the information in the table above on skin microflora to label themicroflora present on the sites indicated on the diagram below.


b) Explain what could happen to skin microflora and the skin if aproduct was used with a pH of 9.

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22 Draw five diagrams showing oil being acted on by an emulsifier.Explain what is happening at each stage.

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Exercise 6.4

You should have made significant progress on your open-endedinvestigation. Your completed report should be sent to your teacher withthis section, unless another date has been specified by your teacher.

Use your own paper to complete your report based on your plan fromExercise 3.4.

The following information outlines what your teacher expects in yourreport.

Aim

What are you trying to find out? What product(s) are you testing?

Apparatus

What and/or who will you need to carry out your investigation?

Method

How will you carry out your investigation? Organise each stepsequentially. How will you collect results? Will your data bequantitative (measured) or qualitative (compared against each other)?

Indicate your dependent variable (what you are interested in measuring)and independent variables (quantities that could affect the value of yourdependent variable measurement). Outline how you will ensure variablesare kept constant and what your control will be.

Results

How will you present your results? Will you use a table? Will youinclude photographs or draw a graph? Indicate if your results are to bequantitative (measured) or qualitative (compared against each other).

Discussion

Did the product match the claims? Did anything bias your results or gowrong? How could the method have been improved? Would youidentify the product as a solute, solvent, solution, colloid or suspension?What evidence do you base this on?


Conclusion

Did the product match the product’s claims? Why or why not? Use yourresults with your explanation. Can you relate this information toanything you have learnt in Lifestyle chemistry eg. solubility, skin pH orskin microflora?

When presenting your report:

• Remember to use scientific language in your investigation.

• Don’t be afraid to include pictures, diagrams, graphs and tables andinformation from other sources – these will often attract extra marks.

• Refer to the Science Resource Book or contact your teacher if you’renot sure how to approach the discussion and conclusion.

Good luck with your report!

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Bibliography

• Lewis, R and Evans, W. 1997. Chemistry. Macmillan Foundations,Hong Kong.

• Sharwood, J. 2000. Nelson chemistry. Nelson Thompson Learning,Melbourne.

• Selinger, B. 1989, Chemistry in the Marketplace, Fourth Edition.Harcourt Brace Jovanovich Group Pty Ltd. Sydney.

• Barker, A and Knapp, K. 1983. Chemistry - a practical approach.Macmillan Education Limited, Hong Kong

• Garnett, P. 1992. Foundations of Chemistry. Pearson EducationAustralia.

• Noble, W. 1993. The Skin Microflora and Microbial Disease.Cambridge University Press. Victoria. Australia.

• Tannock, G. 1995. Normal Microflora. Chapman and Hall.London.

• Laidler, G. 1991. Environmental Chemistry – an AustralianPerspective. 2nd Edition. Pearson Education Australia.

• Chemical Fact Sheets. ICI. Australia. Melbourne.

• Orion Laboratories Pty Ltd. Western Australia. Material safety datasheets. http://www.orion.net.au/ (accessed 4 July 2000).

• Conte, U and Maggi, L. Geomatrix® system• for controlled release ofdrugs. Department of Pharmaceutical Chemistry. University of Pavia.Italy. <http://www.unipr.it/arpa/dipfarm/conf/abstracts/conte.html>(accessed 20 June 2000).

• Prell, G. Drug absorption, Distribution and Elimination. MountSanai School of Medicine. City University of New York.<http://www.mssm.edu/pharmacology/ParmCourse/Syllabus1998/>(accessed 18 June 2000).

• Gabard B, Elsneer P, Surber C and Treffel P. 1999.Dermatopharmacology of Topical Preparations. A product-development oriented approach. Springer-Verlag. Berlin.


• Uno, H. The Histopathology of Hair Loss. Wisconsin RegionalPrimate Research Centre. University of Wisconsin.<http://www.npntserver.mcg.edu/html/alopecia/documents/>(accessed 1 May 2000).

• Nursing Times. 4/10/1973 Noble, W. Commensal bacteria ofhuman skin.

• Theil, W J and Panagiotidis, J. Controlled Release Drug Delivery.Department of Pharmaceutics.<http://www.vcp.monash.edu.au/pharmaceutics/res-control.html>(accessed June 17 2000)

SSCHSC 43168 Lifestyle chemistry

Student evaluation

Name: ________________________ Location: ______________________

We need your input! Can you please complete this short evaluation toprovide us with information about this module. This information willhelp us to improve the design of these materials for future publications.

1 Did you find the information in the module clear and easy tounderstand?

2 What did you most like learning about? Why?

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3 Which sort of learning activity did you enjoy the most? Why?

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4 Did you complete the module within 30 hours? (Please indicate theapproximate length of time spent on the module.)

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