Nuffield co-ordinated sciences: chemistry worksheetsmypchem.com/root_pdf/Chemistry_Worksheets.pdf · NUFFIELD CO-ORDINATED SCIENCES CHEMISTRY WORKSHEETS Worksheet C2B [side 1] Cracking

NUFFIELD CO-ORDINATED SCIENCES CHEMISTRY WORKSHEETS

Contents

CO Planning sheet C9A Investigating colloids

CIA Reacting moleculesC9B Surface tension

CIB The Periodic TableC9C Making a cosmetic cream

C2A Making models of molecules: part 1CIOA Comparing detergents

C2B Cracking hydrocarbonsCIOB Which is the best way of softening water?

C2C Making models of molecules: part 2 CllA Dyeing with indigo

C3A Plant productsCllB Mordant dyeing

C3B Investigating carbohydrate moleculesCllC Dyeing with a reactive dye

C3C Models of carbohydrate molecules Cl2A How much gastric juice does 'bicarb' neutralize?C3D Enzymes Cl2B Analysis of a magnesia tablet

C4A Making alum from shaleC12C Analysis of aspirin tablets

C4B The story of the alum industry Cl3A FuelsC4C Investigating the electrolysis of a solution of Cl3B What makes a good fuel?

sodium chloride C13C Choosing a good fuelC4D Chemicals from salt Cl3D Measuring the energy released by burning fuelsC4E The limestone inquiry C13E Air pollution - where does it come from?C4F Making aluminium

Cl4A Investigating cellsC5A Molecules or giant structures?

Cl5A Particle size and the rate of reaction of a rockC5B Ions on the move

with an acidC5C Ions and electrolysis

Cl5B Concentration and the rate of reaction of a rockC5D Lawrence Bragg and the start of X-raywith an acidcrystallogra phy

Cl5C Temperature and the rate of reaction of a rockC6A Making glass with an acidC6B Glass working Cl5D Investigating the effect of pH on the solubilityC6C Float glass of soil minerals

C7A Properties of metals Cl6A The catalyst crisisC7B Analysing an alloy Cl6B Making a fertilizer

CSA Polymerization Cl7A A shortened form of the Periodic TableCSB The label at the back - a look at clothing fibres Cl7B The Periodic TableCSC Polymers all about us

CISA Ions into molecules at the anodeCSD A key to identify plastics

© Nuffield-Chelsea Curriculum Trust 1988. 1~llil[[il!li~llr~1~1mIN12603

Printed by H Charlesworth & Co Ltd. Huddersfield


Worksheet COPlanning sheet

Name(s) of the members of the group:

This is what we plan to do:

Safety precautions:

The problem(s) we intend to investigate:

Diagram:

The equipment we need from The chemicals and other Equipment and materials whichschool: consumables we need from school: we will bring from outside school:

Information we intend to get from reference books and other printed sources, and the references we plan toconsult:

© Nuffield-Chelsea Curriculum Trust 1988.


Worksheet Cl AReacting molecules

Cut out the 15 'pages' of the flick book. Arrange them in order with number 1 on top.Then staple the book together.

3

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0..Ctlen

4

Q)

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Q)

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ci5

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W0.. 0.. 0..Ctl Ctl Ctlen en ci5

10 11 12

~ ~ ~(J) Q) Q)

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13 14 15

Q) Q)

Cii iiiQ) ..r::: ..r:::Cii Q) Q)

..r::: 0.. 0.(J) co co0. en encoen



Worksheet Cl BThe Periodic Table

- -

H He

Li Be B C N a F Ne

Na Mg AI Si P S CI Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La Hf Ta W Re as Ir Pt Au Hg TI Pb Bi Po At Rn

- ~

r---- -


NUFFIELD CO-ORDINATE[) SCIENCES CHEMISTRY WORKSHEETS

Worksheet C2AMaking models of molecules: part 1

Yau will need:

•

4 carbon atomsC black

four holes •

4 oxygen atomso redtwo holes

(:\ 10 hydrogen atoms~ white

one hole

1111111111111111111111111111111111 4/ong bonds and 10short bonds to hold

1111111111111111111111 the atoms together

Part A: Models of simple moleculesMake a model of each of the following molecules. Use the short bonds with thehydrogen atoms.

hydrogen, H2; water, H20; oxygen, O2; carbon dioxide, CO2•

Ouestions

1 Which of these substances are elements and which are compounds? How can youtell just by looking at the formulae or the models?2 Which of the models include double bonds?

Part B: Models of alkanesMake models of the molecules of the first four members of the alkane series: methane,ethane, propane, and butane. (Look up the formulae in a book, or table of data.)

Ouestions

3 Why are the alkanes called hydrocarbons?4 Predict the formulae of the next two members of the series: pentane and hexane.

Part C: Different molecules with the same formulaUse your models to show that there are two ways of joining atoms to makemolecules with the formula C4H10.

Ouestions

5 Of the two models you have made, which would you call the straight chaincompound and which would you call the branched chain compound?6 The straight chain compound boils at - 0.5 °C. The branched compound boils at-12°C. Look at the models and try to suggest a reason for the difference.

Part D: A model equationUse your models to show how the atoms are rearranged during this reaction. Firstmake the reactant molecules, then rearrange them to produce the products.

CH4 + 202 - CO2 + 2H20

Ouestions

7 Write a word equation for the reaction; then rewrite the symbol equation above,using graphical formulae.8 Which comes first in a reaction: bond breaking or bond forming?



Worksheet C2B [side 1]Cracking hydrocarbons acidified potassium manganate(vlI)

bromine water

when the tube is full,stopper it and thenfill two more tubeswith the gas

0

0 water

0bunsen valve

0 which helps

0to stop suck back

-- clamp as near toend of tubeas possible

catalyst

heat the solid strongly

3-4 cm depth ofmineral wool soakedwith a hydrocarbon oil

ProcedureIISet up the apparatus as

shown in the diagram. Thereis a choice of catalysts. Startby using aluminium oxide.

IIHeat the catalyst strongly fora few minutes. While keepingthe catalyst hot, flick theflame from time to time tothe end of the tube with theoil and mineral wool. Try tocontrol the heating toproduce a steady flow ofgas.

IIDiscard the first two tubesof gas you collect. This makessure that all the air hasbeen removed from theapparatus.

IICollect three tubes full of gas and stopper them. Keep the gas for testing as shown under the heading'Results'.

Warning:Remove the delivery tube from the trough when you stop heating so that water does not suck back into thehot test-tube. Hold the stand to lift the apparatus because the clamp will be hot.

Results1 Test your samples of gas as shown in the table. Repeat the tests with a few dropsof the hydrocarbon oil.

Test Results with the gas formed Results with the hydrocarbonduring the experiment oil

Describe what the samples look like.

Do the samples of gas and oil smell?

Try to light the gas. Will a few drops ofoil on a crucible lid catch fire?

Add one or two drops of dilute, acidifiedpotassium manganate(vn), then shake.

Add one or two drops of aqueousbromine and then shake.

_______________________________ CONTINUED© Nuffield-Chelsea Curriculum Trust 1988.

NUFFIEL[) CO-OR[)INATE[) SCIENCES CHEMISTRY WORKSHEETS

Ouestions2 Which two elements are present in the oil at the start of the experiment?

3 Compare the properties of the product of the reaction and the oil. What is thereto show that the reaction has turned larger molecules into smaller ones?

4 Why can you assume that the product is a hydrocarbon?

5 Why is the process taking place in this experiment called cracking?

6 Which is the more reactive: the oil or the product of the reaction?

7 What are the two products of the reaction when the gas burns?

8 What is happening when the product reacts with bromine? Why is there a colourchange?

9 What is the evidence that the oil is a saturated compound while the product isunsaturated?

Further investigations10 There is a choice of catalysts for this reaction. If you have time you can try todiscover by experiment which is the best catalyst. In addition to aluminium oxide, trya coil of copper gauze, pottery chips, or a plug of iron wool.• How will you judge which catalyst is most effective?• What measurements, if any, will you need to make?



Worksheet C2CMaking models of molecules: part 2

Yau will need:

•4 carbon atomsblackfour holes

•1 oxygen atomredtwo holes

•2 bromine atomsgreenone hole

o8 hydrogen atomswhiteone hole

11111111111111111111111111111111111

111111111111111111111

4 long bonds and8 short bondsto hold the atoms together

Part A: Saturated and unsaturated hydrocarbonsMake a model of each of these two hydrocarbons: ethane, Cz H6 and ethene, Cz H4•

Questions

1 Write down the graphical formulae for the two hydrocarbons.2 Which of the compounds is an alkane?3 Which of them is a saturated compound and which is unsaturated?

Part B: CrackingUse your models to show what happens when ethane is cracked to make ethene andhydrogen.

Questions

4 Use graphical formulae to show what happens when ethane is cracked.5 Write a balanced symbol equation for the cracking reaction.

Part C: Molecules adding togetherUse your models to show how the atoms are rearranged in each of these reactions.First make the reactant molecules, then rearrange them to produce the products.

CZH4 + HzO - CzHsOH

CZH4 + Br z - CZH4Br z

Questions

6 Write a word equation for each reaction, then write the equation again usinggraphical formulae.7 What colour changes would you expect, if any, during these reactions?

Part 0: PolymerizationNow make two ethene molecules and combine with the other groups in the class topolymerize them and produce poly(ethene).

Questions8 Draw a diagram to show several ethene molecules polymerizing.9 Which part of an ethene molecule makes it more reactive than ethane?



Worksheet C3APlant products

Plant product What the product Which plant the Artificial alternativesis used for product comes from to the natural

product (if any)



Worksheet C3B [side 1]Investigating carbohydrate molecules

Start by carrying out the tests described on this side of the worksheet. Practise thetests until you know what to expect with each of the carbohydrates. Then turn toside 2 for an investigation which will make use of the tests you have learned to use.

Tests for sugars and starch

iodine solutionBenedict's solution

Iodine solution

add a few drops

of ~dine solution =t\ Benedict's test

2-3mlofthecarbohydrate solutionmixed with an equalvolume of Benedict'ssolution

carbohydratesolution to betested

IIUl

hot water

lIJU

Try the two tests with these carbohydrates: glucose, sucrose, fructose and starch.Carefully note the main changes, especially the colour changes, and record them in atable.

Carbohydrate Result of the iodine test Result of Benedict's test

GlucoseSucroseFructoseStarch

Ouestions1 What does it mean if you test something with iodine solution and the result is adeep blue or black colour?

2 Which of the carbohydrates you have tested react with Benedict's solution? Whathappens when Benedict's test gives a positive result?

© Nuffield-Chelsea Curriculum Trust 1988.CONTINUED


iodine solutionBenedict's solution

Does stomach acid affect the carbohydrates we eat?The idea of this investigation is to find out whether stomach acid has any effect onthe carbohydrates we eat. Does the acid help with digestion?

The acid involved is hydrochloric acid, and you will be supplied with a solution ofthis acid of about the same concentration as stomach acid.

You should plan an investigation to find out whether stomach acid has any effecton the carbohydrates studied on side 1 of this worksheet. You can use the two testswhich you have just practised to see whether there are any changes.

Here are some of the questions which you may want to think about as you makeyour plans:

• What will you use as a model stomach?• How will you keep the stomach at body temperature?• How much acid will you put in your model stomach?• Will you add the carbohydrates one at a time, or in a mixture?• Will you add the carbohydrates as solids or in solution?• How much carbohydrate will you add?• How will you remove samples from the 'stomach' for testing?• How often will you take samples and test them?• Which tests will you use? (You will have to neutralize the stomach acid in thesamples with sodium carbonate before doing the tests.)• How long will you continue taking samples?• How will you record your results?

Write down your plans and include a list of the apparatus and chemicals you willneed. Then show your plans to your teacher.



Worksheet C3CModels of carbohydrate molecules

You will need:

•

6 carbon atomsC black

four holes •

6 oxygen atomso red

two holes o 12 hydrogen atomswhiteone hole

1111111111111111111111111111111111

1111111111111111111

12 long bondsand12 short bonds

Part A: Models of simple sugars (monosaccharides)Make a model of either glucose or fructose. (It will help if your group makes one ofthem and your neighbours make the other.) Use the short bonds for the hydrogenatoms.

CH20HIC--O

~/~ ~~C C

Ho~9H ~/bHC--CI I glucoseH OH

Part B: A model of a double sugar (disaccharide)Work with your neighbours. Join together a glucose molecule and a fructosemolecule to make a sucrose molecule and a water molecule.

Now carry out the reverse reaction and split sucrose back into the two simple sugars.

Part C: Models of long chain carbohydrates (polysaccharides)Make your set of atoms into a glucose molecule.

Now work with several other groups and join your glucose molecules to make asmall fragment of a starch molecule.

Rearrange your model so that the glucose molecules are joined together to make amodel of a cellulose molecule.



Worksheet C3D [side 1]Enzymes

This worksheet is designed to help you study section C3.4 in your Chemistry book.You have here a copy of part of the text so that you can write on it. Most of thepictures are not included but you can look at them in the book.

Study guideIIRead the passage carefully and look at the diagram.

IIUse different coloured pens for each stage of marking and underlining the text.First, underline two sentences which you think give the clearest idea of what an

enzyme is. (The sentences need not come together in the text.)Second, underline the words which tell you about the things which enzymes do

naturally in plants and animals.Third, underline the words which tell you about the way enzymes are used in

the home and in industry.

IINow write notes under these headings:• What is an enzyme?• What do enzymes do in living things?• How do we use enzymes in the home and in industry?

How does all this clever chemistry happen in living things?In chemistry we use catalysts to speed up reactions. In the petrochemical industry, forexample, catalysts are involved in the cracking of hydrocarbons and thepolymerization of ethene. Catalysts make reactions go at a lower temperature thanmight otherwise be necessary.

There are many catalysts in living things too and these catalysts are called enzymes.Enzymes control all the chemical reactions in the cells of plants and animals. Thereare enzymes for the reactions which take small molecules and join them to makebigger ones. There are also enzymes which start with big molecules and break themup into smaller ones. All the reactions in cells which enable living things to digestfood, move, grow, and reproduce are controlled by enzymes.

Each reaction has its own enzyme. The enzymes which join glucose moleculestogether to make starch are different from the enzymes which join glucose to makecellulose.


NUFFIELD CO-ORDINATED SCIENCES CHEMISTRY WORKS·HEETS

]

The way in which enzymes make chemical reactions go faster at a lowertemperature is illustrated by the difference between bees making honey and ourmaking jam. Both processes involve a reaction called inversion. Food labels oftenmention inverted sugars and you may have wondered what this means.

Bees get their sugar from the nectar of flowers. We get our sugar from cane orbeet. In both cases the sugar is sucrose. Sucrose consists of two simpler sugars,glucose and fructose, linked together as in the diagram. The diagram also showssucrose being split into glucose and fructose by reaction with water. This is theprocess of inversion.

sucrose

CHzOHIc--o

H/I "'" HI H ""'IC CI'" OH H/ IHO "'I I OHc--c

I IH OHglucose

Iinve~i.n

+

fructose

Sucrose reacting with water to give glucose and fructose.

Jam is about 60 per cent sugar; the rest is water and fruit. The high concentrationof sugar is a preservative which stops it going mouldy. The mixture of fruit, waterand sugar is boiled during jam making; boiling continues until the temperaturereaches about 105 °e. At this high temperature some of the sucrose reacts with waterand turns into glucose and fructose. Acid from the fruit acts as a catalyst for thereaction. So the sugar in jam is a mixture of sucrose and inverted sugar. This isimportant, because the mixture is much more soluble in water than sucrose is on itsown. This means that the sugar doesn't crystallize when the jam is put into jars andcooled to room temperature.

Bees invert sugar when they make honey. They can do this at their bodytemperature with the help of the enzymes they produce.

Plants and animals can do lots of clever chemistry in their cells because ofenzymes. We depend on the enzymes in bacteria and fungi to maintain the naturalcycles in the environment. We have used yeasts and their enzymes for thousands ofyears in baking and brewing. Recently it has been realized that there are many moreways by which we can take advantage of enzymes. For this reason, biotechnology hasbecome very important. Among other things, research into biotechnology is aimed atproducing better and cheaper drugs, alternative sources of energy, and new types offood.


NUFFIElD CO-ORDINATED SCIENCES CHEMISTRY WORKSHEETS

Worksheet C4A [side 1]Making alum from shale .~ lXJ

dilute potassium hydroxide dilute sulphuric acid

In this experiment you are going to practise a variety of practical skills as you makea pure chemical from crushed rock.

Make notes to remind you of what you see happen during each of the steps a to f.

IIHeat 10 g of high alumina shale fiercely on atin lid. Stir the shale with tongs from time totime. Continue heating for 10 to 15 minutesuntil the whole sample is light brown. Then letthe shale cool for 5 minutes.

II Transfer the shale to a beaker. Add 20 ml ofdilute sulphuric acid. Cover with a watchglassand boil gently for 5 to 10 minutes.

watchglass

20 ml dilutesulphuric acidroasted shale

tin lid'"

high alumina _shale (10 gl

add potassium ~hydroxide solutionbit by bit

funnel __ ~

aluminium sulphatesolution

stir with aglass rod

IIFilter to remove the spent shale. (This will bequicker if you use a fluted filter paper.)

Ievaporating basin

IIPour the solution into an evaporating basin.Heat to boiling. Evaporate about half of thewater. (Control the heating carefully so thatthe boiling solution does not spit.)

IIStir the solution and add potassium hydroxidesolution. Go on adding the alkali until the pHis 4. You will need between 5 and 10 ml.Measure the pH by using the glass rod to putdrops of the solution onto indicator paper.

Filter again before going on to step e if asolid appears.

alum crystals

IILabel the basin and set it aside. Leave thesolution to cool and crystallize.

_______________________________ CONTINUED

© in this format Nuffield-Chelsea Curriculum Trust 1988. Based on an experiment devised by the Mineral Industry Manpower and Careers Unit.


Results1 Draw a diagram of the alum crystals you have made. Use a hand lens or a lowpower microscope to examine the crystals.

Ouestions2 What type of chemical reaction takes place during step a?

3 What type of chemical reaction takes place during step d?

4 Why do the instructions tell you to evaporate only about half the water in step e?What would happen if you boiled away all the water?

5 Describe how you would try to grow a single, large crystal of alum.

6 What problems might arise if you tried to carry out this process on a larger scale?

© in this format Nuffield-Chelsea Curriculum Trust 1988. Based on an experiment devised by the Mineral Industry Manpower and Careers Unit.


Worksheet C4B [side 1]The story of the alum industry

This worksheet is designed to help you study section C4.2 in your Chemistry book.You have here a copy of part of the text so that you can write on it. The pictures arenot included but you can look at them in the book.

Study guideIIRead the passage carefully.

III Use different coloured pens for each stage of marking and underlining the text.First, underline all references to the raw materials used to make alum.Second, mark and number in the text the stages in the manufacture of alum.Third, underline the parts of the passage which tell you anything about

chemical changes during the process.

IIConstruct a flow diagram to show what happened during the manufacture ofalum. Draw boxes for the numbered stages and connect them with arrows.

Write inside each box anything you are told about the chemical changesinvolved.

Add labelled arrows to show the stages at which the raw materials areintroduced.

IIGive your flow diagram a title.

How was alum made from rocks?Alum was probably the first pure chemical to be manufactured in Britain. Alum wasused for tanning of leather and for making good quality paper; but by far and awayits most important use was for dyeing wool. During the seventeenth and eighteenthcenturies the production of woollen cloth was the main industry in England. Naturaldyes were used to colour the cloth, and alum was needed as a mordant. A mordant isa chemical used to help dyes to cling fast to cloth so that the colour does not fade inthe light or during washing.

The main centre of the alum industry was on the North East coast of Englandnear Whitby. The mixture of ingredients used in the process seems remarkable: itincluded rock, seaweed, coal, wood, and human urine. The industry lasted for about270 years from 1600 to 1870, but for most of that time there was no understanding ofthe chemistry involved. It was a risky business, and large sums of money were lostelsewhere in England when attempts to make alum failed at places such as Alum Bayin the Isle of Wight and Alum Chine near Bournemouth.

Alum made in England had to compete with alum imported from Italy and otherparts of Europe. Both James I and Charles I issued proclamations which were meantto ban foreign imports and protect the home market. This shows the economicimportance of the alum industry at that time.

The alum was made from a hard but crumbly rock which the workers could digfrom the cliffs near the coast. All the labouring was done with pick, shovel andwheelbarrow, but over the years they shifted huge tonnages of rock. The derelictquarries can still be seen near Whitby.

We now know that this rock could be used to make alum because it containedaluminium silicate, iron pyrites (iron sulphide), and some organic material whichhelped to keep the fires going.

The workers laid fires of brushwood. Over the top they built huge piles of thebroken rock. The heaps could be as much as 30 metres across and 25 metres high.The coal to fuel the boiling-house fires was shipped from Sunderland and Newcastle.



he

In the whole process something like 6 tonnes of coal were needed for each tonne ofalum produced, so the price of coal was a major part of the production cost.

The roasting of the rock took many months. Slow burning was essential. We nowunderstand that, during the burning, some of the sulphur in the iron pyrites wasturned into sulphuric acid. The acid then reacted with aluminium silicate in the shaleto make aluminium sulphate.

After roasting, the burnt rock was tipped into pits of water. The water was stirredwith long wooden poles and then allowed to settle for several days. The aluminiumsulphate dissolved while the waste material sank. The solution of aluminium sulphatewas run off along wooden troughs to large boiling-pans made of lead in a centralboiling-house. These pans were about 3 metres long, 2 metres wide, and 2 metresdeep.

Boiling the solution for twenty-four hours made it more and more concentrated.Every so often, more of the dilute solution was added so that the pans did not boildry.

After cooling, an extract of burnt seaweed or urine was added to the concentratedsolution. The mixture was allowed to stand and then run into 'roaching casks'. Aftera day or two, crystals of alum formed. The roaching casks were broken apart and thecrystals broken up and bagged for transport to London by ship.

The ash from the burnt seaweed contained potash (potassium carbonate, K1C03).

A single alum works needed up to 30000 tonnes of wet seaweed per year. To meetthis demand, seaweed was harvested from as far away as Essex and Orkney. This wasa major industry as potash was also needed to make soap and glass. At that timethere were no easy methods for manufacturing alkali.

The only other suitable alkali was stale urine which contains ammonia. Localpeople stored urine in wooden pails, and it was collected in 25-gallon barrels.Transport by land was relatively expensive, and so much urine was needed that itwas imported by sea from London. Casks were set up here and there in the streets ascollection points. The ships which delivered alum to London returned laden withurine.



Worksheet C4CInvestigating the electrolysisof a solution of sodium chloride

chlorine

~

~sodium hydroxide

sodium chloridesolution

indicatorpaper

carbonelectrodes

sodium chloridesolution

small test-tubes tocollect anygas formed

6V d.c.power supply

II• Support the electrolysis cell with a standand clamp (or with a tripod).• Fasten a piece of indicator paper to eachelectrode. (Cut a slit in the paper and push itover the electrode.)• Pour some sodium chloride solution intothe cell.• Switch on and watch what happens aroundeach electrode. Note carefully which electrodeis the anode and which is the cathode.

Results1 Put your results in a table like this.

6Vd.c.power supply

II•Remove the indicator paper.• Fill two small test-tubes with sodiumchloride solution. (You may be able to do thisby holding them under the surface of thesolution in the cell.)• Support the tubes over the electrodes.Switch on the power supply and collectsamples of any gases formed at the electrodes.• Use tests to identify the gases.

Electrode Was the indicator Did the pH change Did a gas form? If so, how did you testpaper affected? near the electrode? it? What was the gas?

Anode(posi tive electrode)

Cathode(negative electrode)

Ouestions2 Which four elements are present in a solution of sodium chloride in water?3 Which of the four elements named in your answer to question 2 are removed atthe electrodes during electrolysis?4 What might be formed in solution as electrolysis takes place?Would you expect this substance to be acidic or alkaline?Does this explain the pH changes observed around the electrodes?



Worksheet C4DChemicals from salt

Study guide1:1 Read the following passage carefully and look at the diagram.

III Some words are missing from the passage. One word fills each of the gaps.Discuss with your group the best word for each gap and then fill the gap. Manyof the missing words can be found on the diagram, but not all of them.

IIWhen you have filled the gaps, write the chemical symbol for each of thesubstances shown on the diagram alongside its name.

IIFinally write a few words of comment or explanation beside each label on thediagram.

Manufacturing processesThere are huge, underground deposits of salt in Cheshire. A little of the salt is minedunderground by cutting, drilling and blasting. The largest mine is at Winsford, wherean output of up to 2 million tonnes of salt is used mainly to supply local authoritieswith the crushed salt which they spread on roads in winter to melt snow and ice.Ground rock salt is also an ingredient of the fertilizers used to grow sugar beet. In1982 it was estimated that there were 35 million tonnes of rock salt which could besafely and economically mined at Winsford.

Most of the salt used in the chemical industry is not dug out; it is extracted bypumping water down into the rock. The salt dissolves and is carried to the surface asa solution called brine.

Brine is the main raw material for the manufacture of two important industrialalkalis: sodium hydroxide and sodium carbonate. The demand for these alkalis ishuge. Worldwide we use about 36 million tonnes of sodium hydroxide and 26 milliontonnes of sodium carbonate each year.

sodium chloride solution---+

An electrolysis cell

chlorine gas

io 0000

+positive titaniumelectrode

hydrogen gas

i

negative nickelporousmembrane electrode

sodiumhydroxide

solution-.

Brine is a of sodium chloride, NaCI, in , H20. So there arejust four elements in brine which can be rearranged to make sodium hydroxide,NaOH, chlorine, C12, and hydrogen, H2• The method used to rearrange the elementsis . Chlorine is given off as a gas at the electrode (the anode)and forms at the negative electrode (cathode). The cellused for the electrolysis of brine has to be carefully to stop the chlorineand sodium hydroxide reacting together to make bleach. The in thecell allows the solution to pass through but stops the chlorine mixing with the



Worksheet C4EThe limestone inquiryGeneral briefing [side 1]You are going to take part in an imaginary Public Inquiry concerning a limestonequarry.

Limeco Ltd have a large limestone quarry set in beautiful country in the PeakDistrict National Park in Derbyshire. Limeco have asked the National ParkAuthority for planning permission to extend the quarry. They want to double theamount of limestone produced. The Authority has refused permission. Limeco haveappealed against the decision, and now there is to be a Public Inquiry.

You will be playing a part in the Inquiry, and later you will have to read a specialbriefing about that part. But first you should read the rest of this General Briefing.

What is limestone?

Limestone is calcium carbonate, CaC03. It is formed from the remains of organismsthat lived in ancient seas 300 million years ago. The limestone that occurs in thePeak District is especially pure, so it is very useful, particularly for the chemicalindustry.

Figure 1Map showing the Peak District

Manchester•

PEAKDISTRICTLIMESTONE

Sheffield•

Figure 2Blasting limestone. 60000 tonnes are blasted at a time

What happens in a limestone quarry?

Over a million tonnes of limestone are taken from the Limeco quarry every year.Explosives are used to blast the rock from the quarry face (figure 2). The quarry faceis 2 km long and 30 m high.

The rock is loaded onto huge lorries and taken for sorting into pieces of differentsize. Part of the limestone is processed on the quarry site. It is used to make otherthings such as cement and quicklime. Part is carried away by rail or road tocustomers who use limestone itself. A lot of limestone is used for aggregate.Aggregate is lumps of rock or stone used to make concrete or in road-building.

- CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 602. © in this format Nuffield-Chelsea Curriculum Trust 1988.


o he E

[side ]What is limestone used for?

Figure 3 shows the main ways limestone is processed on the quarry site.

LIMESTONE I :>LUMP LIMESTONECaC03 .----- for steel making, making sodium carbonate,

aggregate for concrete, road making, etc.

grind ~ POWDERED LIMESTONE----V for agriculture, making glass, etc.

heat QUICKLIME CaOfor agriculture, industrial drying agent etc.

I add water :>SLAKED UME Ca(OHbfor agriculture, purifYIng water, making mortar,pottery, chemicals, dyes, solvents, paints,medicines

heat with clay CEMENT

Figure 3Some of the ways limestone is processed, and the main uses

Figure 4 shows the layout of the main parts of the Limeco quarry.

~

~limesto~e "processingunit

Figure 4Layout of main parts of quarry

cement plant

CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 602. © in this format Nuffield-Chelsea Curriculum Trust 1988.


]What you will be doing

At the Public Inquiry there will be a group of Inspectors who will listen toarguments for and against the quarry extension. These arguments will be put by thefollowing groups:

For: Representatives of LimecoRepresentatives of Industrial Users of LimestoneRepresentatives of Trades Unions

Against: Representatives of the National Park AuthorityRepresentatives of Local ResidentsLocal Conservation Group

During the Inquiry you should bear in mind the 'Silkin Test'. This is three conditionswhich must be satisfied before planning permission can be given to extract mineralsin a National Park.

1 There must be a clear need for the mineral which no other mineral can meet.

2 There must be no other source of supply.

3 The quarry company must guarantee to restore the site after use.

(These conditions are called the 'Silkin Test' after the Minister, Lewis Silkin, whoguided the 1949 National Parks and Access to the Countryside Bill through theHouse of Commons.)

Figure 5Limestone processing equipment at a large quarry in the Peak District

Copyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 602. © in this format Nuffield-Chelsea Curriculum Trust 1988.


The InspectorsYou are one of the panel of Inspectors in charge of the Public Inquiry. You have tolisten to the various arguments put forward, then present a report to the Secretary ofState for the Environment.

While listening to the arguments you must bear in mind the three conditions of the'Silkin Test', given in the General Briefing.

Before the Inquiry starts you should decide who will be the Chairperson of thepanel of Inspectors. Your Chairperson will do the speaking at the meeting.

It will be the job of the Inspectors to run the Inquiry and keep order. Much of thesuccess of the Inquiry depends on you!

Organizing the Inquiry

PreparationArrange the seating in the room where the Inquiry will be held. Remember there willbe three groups speaking in favour of the quarry extension (Limeco, the quarryoperators; the Industrial Users of Limestone; and the Trades Unions). There will bethree groups against (the National Park Authority; Local Residents; and the LocalConservation Group.)

The Inquiry1 Call the meeting to order. Remind them that they should bear in mind the 'SilkinTest' when they present their arguments. A maximum of two minutes will be allowedfor the presentation of arguments. During the speeches, do not allow anyone tointerrupt.

2 Call on the representatives of Limeco to state their case appealing against thedecision by the National Park Authority not to allow the quarry extension.

3 Call on the representatives of the National Park Authority to explain why theyrefused planning permission.

4 Call first on the Industrial Users of Limestone, then on the Trades Unions tosupport the case made by Limeco.

5 Call first on the Local Residents and then the Local Conservation Group to maketheir case against the extension.

6 Give everyone a final opportunity to answer points made by opposing groups. Ifyou think there are any matters which have not been clearly explained, ask questionsto help clear them up. Do not allow anyone to talk too much!

7 Close the Inquiry by saying when you will be publishing your report with itsrecommendations.

After the InquiryAfter the Inquiry you will consult together and write a short report stating whetheror not planning permission should be granted. If permission is granted you shouldstate any conditions to be met by the quarry operators. You will submit your reportto the Secretary of State for the Environment (your teacher) who will announce thefinal decision in about six months time - or possibly sooner.



heI I

Representatives of LimecoYou represent Limeco, the quarry operators. At the Inquiry you will have to presentyour arguments for extending the quarry.

You and the other representatives should first read this briefing. Then discuss thearguments you will put forward in a two-minute presentation at the Inquiry. Youmay want to elect a single person to speak, or share it between you.

The main points of your case

• You argue that the quarry has been a supplier of high quality limestone toindustry for a long time. Transport links already exist and modern equipment(including kilns and crushing plant) is already on the site. To start a new quarryoutside the Park would be very expensive because of the cost of new roads and newplant.

• It is unfortunate that the best, high purity limestone occurs in areas of naturalbeauty. However, extension of an existing quarry will have less effect on theenvironment than opening a new quarry somewhere else.

• New wheel-washing equipment will be installed to ensure that lorries do notdeposit mud on the roads. New roads built to the quarry extension will be tarred toreduce the nuisance of dust and mud.

• Tree planting and landscaping will be carried out around the site before quarryingstarts on the extension site. In the new part of the quarry the faces will be about 20metres high instead of 30 metres as in the old quarry. This will reduce the visualimpact of the extension.

• You consider that the extension will allow a much more natural restorationscheme for the whole site when quarrying ends. Restoration will produce a new dalewhich will in time look natural. You will restore the whole site for recreational usewhen quarrying finishes.

• If the quarry extension is permitted you will be able to increase your grants totwo university groups who are investigating better ways of restoring quarries afteruse. You will also make grants to local trusts who are developing abandoned quarriesin the area as nature reserves.

Note You may decide not to use all these arguments when making your initialpresentation to the Inspector. You may want to keep some of the points in reserve,ready to answer points made by groups opposing the quarry extension.

Copyright © Association for Science Education 1986. Taken from ASE SAliS Unit No. 602. © in this format Nuffield-Chelsea Curriculum Trust 1988.


r

Industrial users of limestoneYou represent some of the industrial users of the limestone quarried by Limeco. Atthe Inquiry you will have to present your arguments in support of the extension tothe quarry.



• For industrial purposes it is essential that the calcium carbonate used is pure. Anyimpurities have to be removed, and this requires extra and expensive processes. Thereis also the problem of disposing of the waste impurities.

• Limestone deposits are widely distributed in Britain and are quarried for manydifferent uses. The deposits in the Peak District of Derbyshire are particularly useful.They are very pure. The deposits are easy to get at. They are near to the bigindustrial centres of the Midlands and the North, but unfortunately they are also inareas of outstanding beauty.

• Limestone from this district has supplied the chemical industry in Cheshire andSouth Lancashire since the early nineteenth century. The quarry operatorsunderstand the needs of the chemical industry. There are suitable transport links byrail and road. It would be very disruptive socially and economically if other supplieshad to be found.

• The National Park Authority considers that too much of the limestone is beingused for aggregate in road-building and for concrete. You will therefore wish to stressthe important uses of limestone in the chemical industry, in agriculture and insteelmaking. Figure 3 in the General Briefing summarizes some of the uses oflimestone and limestone products in industry. You can point out that it isunavoidable that some aggregate is produced. This is because only part of thelimestone is of the right size for use in the chemical industry.



Representatives of trades unionsYou represent the trades unions involved in the work at Limeco's quarry. At theInquiry you have to present your arguments in support of the extension to thequarry.



• You represent the people who work in the quarry. The extension will safeguardtheir jobs for up to twenty years.

• You also represent the self-employed lorry drivers who transport two-thirds of thequarry output. The extension will safeguard their employment too.

• Limestone from the quarry is necessary for the steel, glass and chemical industries.It helps to maintain employment in these areas too.

• You realize that local people are affected by noise, dirt and the visual impact ofthe quarry. However, quarry operators make a big contribution to the local rates (seetable).

%Household ratepayers 51Quarry ratepayers 10Other industrial ratepayers 8Commercial ratepayers 11Other non-domestic ratepayers

(for example, water, gas, schools, etc.) 20

Where the local council get their money

• You realize that local people are annoyed by dust and mud from lorries. Some ofthis is caused by workers who do not follow the rules about covering the lorries andwashing mud off the wheels. You are prepared to support the employers to make surethe rules are followed. However, the workers must be allowed enough time in thework schedules.



Representatives of the National Park AuthorityYou represent the National Park Authority, who have refused permission for Limecoto extend their quarry. At the Inquiry you will need to present your argumentssupporting your refusal.



• Your main concern is to preserve the natural beauty, scenery and wildlife of theNational Park.

• You accept that some quarrying is necessary. The quarry produces very purelimestone which is needed by the chemical industry. However, you argue that theneeds of the chemical industry can be met from the present quarry for many years.

• You consider that the extension is only required because too much stone is beingused as aggregate for road building and concrete. Limestone for road building andconcrete can be found outside the National Park. The figures show that over half thelimestone output from National Park quarries is being used as aggregate for roadbuilding.

• Even if you lose the Inquiry, and permission for the extension is given, you feelthere should be strict conditions. There should be conditions on the area of workingand landscaping, and restoration when the quarry is worked out.

• You are convinced that there is no need to take a decision quickly. There is notenough information about the national need for limestone. A national survey oflimestone deposits needs to be carried out. A long-term plan for the extraction oflimestone should be developed. Until this is done no further permission for quarryingin National Parks should be granted.

Copyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 602. © in this format Nuffield-Chelsea CUrriculum Trust 1988.


r he

Representatives of local residentsYou represent the residents living in the area around the Limeco quarry. At theInquiry you will have to present your arguments against the extension of the quarry.



• The quarry is ugly, dirty and noisy. It is only 150 metres from the nearest houses.

Ugly - the quarry is a blot on the landscape, an ugly scar in otherwise beautifulcountryside.

Dirty - you suffer from dust falling in and around your homes. Dust comes fromdrilling, blasting and stone crushing. There is even more dust when they tipwaste on dry and windy days.

Noisy - you suffer from the noise of machinery and traffic.

• The quarry operators say they will restore the quarry at the end of its life.However, you are suspicious because in the past they have not restored quarriesproperly. They have left ugly heaps of waste.

• The lorries from the quarry are too big for the roads. They cause a lot of dirt inthe air and mud on the roads. The lorries are not always covered as they should be.The wheel-washing equipment seems inadequate when the quarry is busy. The lorriesare often driven too fast.

• Limeco say the quarry extension will create extra employment. But statistics showthat employment in the quarries has fallen in the last thirty years (see the table). Solocal people and local shops get less benefit from the quarry even if it does createemployment further away.

Year

Number employed in quarries

1953

4978

1963

4042

1970

3300

1976

2180

Employment statistics in the Peak National Park 1953-1976



o he

Local conservation groupYou are a member of a local conservation group, concerned about the effect of thequarry extension on the local environment. At the Inquiry you will have to presentyour arguments against the extension of the quarry.



• Quarrying limestone permanently changes the landscape. This area was made aNational Park because it has some of the most beautiful scenery in Britain. It shouldbe kept beautiful and natural for everyone to enjoy.

• Quarrying destroys the characteristic vegetation of the district and removes thehabitat of wildlife.

• If permission to extend the quarry is granted, you are very concerned that thequarry site should be properly restored after use. This means making sure the disusedquarry blends in with the landscape. A restoration plan must be produced beforequarrying starts. The operators should also show how they will prepare forrestoration during the working life of the quarry. For example, the planting of treesto screen the site needs to be planned up to thirty years ahead.

• You are worried that the quarry operators will be looking for the cheapest methodfor restoring the site. You insist that restoration must be done properly. You areparticularly concerned that the disused quarry should not be used as a waste tip.

• If permission is granted, you insist that the quarry face should be shallow.Towards the end of the life of the quarry, the face should be left so that it willweather to look like a natural cliff. Ledges and screes should be left which will giveopportunities for colonization by plants.



Worksheet C4F [side 1]Making aluminium

Study guideIIRead the passage carefully and look at the two diagrams.

IISome words are missing from the passage. One word is needed to fill each gap.Discuss with your group the best word for each gap and ~hen fill it in. All thewords you need are in the first diagram (figure 1).

IINow label the second diagram (figure 2) as fully as you can with the help of thecompleted passage.

Where does aluminium come from?Aluminium is an excellent conductor of electricity and so it is used to make wires,transmission cables and electrical equipment. Aluminium is strong but has a lowdensity; this makes it very suitable for making parts of ships, aeroplanes and cars.Aluminium is easily shaped and can be rolled into thin foil, drawn into fine wire, orextruded to give complex shapes. It is non-magnetic, a good conductor of heat, andcan be used as a reflector of light.

The extraction of aluminium is one of the most important industrial uses ofelectrolysis. The main aluminium ore is called --. Aluminium is obtainedfrom bauxite in two stages. In the first stage the bauxite is purified to produce__________ in the form of a white powder. This stage uses sodiumhydroxide to dissolve the aluminium oxide from the ore and separate it from the

Bauxite

sodium hydroxideis used to remove impuritiesfrom the bauxite

Cryolite which dissolves thealuminium oxide when molten

Pure aluminium oxide

Electrolysis cell

the main impurities aresilica and iron oxide

Carbon dioxide

Electrical energy

Figure 1The processing of bauxite toaluminium. Aluminium

In the second stage, the metal is extracted by of aluminium oxide.Compounds of metals with non-metals will only conduct when molten or when insolution. Aluminium oxide has a very high melting-point and it does not dissolve inwater. This means that it is normally impossible to electrolyse it. Extraction of themetal became possible industrially when it was discovered in the 1880s thataluminium oxide will dissolve in cryolite, Na3AIF 6' Electrolysis takes_______________________________ CONTINUED© Nuffield-Chelsea Curriculum Trust 1988.


ide ]

place in rectangular steel tanks lined with carbon. The carbon lining of the tank isthe negative electrode. Aluminium metal forms at the negative electrode and collectsas a molten layer underneath the solution of aluminium oxide in cryolite. From timeto time the metal is drawn off through a siphon tube.

+

Figure 2How aluminium isextracted by electrolysis.

The positive electrodes are blocks of dipping into the molten mixture.Oxygen forms at the positive electrodes so the blocks burn away forming _----. They have to be replaced regularly. The whole process uses hugeamounts of electricity. In a modern aluminium smelter the production of 1 kg ofaluminium requires about 15 kWh of energy. For this reason smelters are usuallybuilt where large amounts of electricity are available relatively cheaply. Hydro-electricity is often the best source of low cost power.



Worksheet C5AMolecules or giant structures? Unknown samples may be

hazardous. so be careful.

In this experiment you are going to test a variety of elements and compounds to seewhether they are molecular or have giant structures. You are looking to see howeasily they melt or evaporate. This will tell you about the strength of the forcesbetween the atoms or molecules.

ProcedureIIPlace a small sample of the substance to be

tested on a tin lid. Some samples must only beheated in a fume cupboard.

1m Heat the sample, first gently then more strongly.

IIDoes the sample melt easily or with difficulty?Does it evaporate? Record your observations ina table like the one below.

a Repeat the experiment with other samples.

Results

[lin lid

1 Record your observations in a table as suggested here. Complete the table as youanswer questions 3 and 4 below.

Name and formula of Changes seen on heating. Type of structure Type of substancesubstance to be tested How easily does it melt or evaporate?

Ouestions2 Are the forces between molecules weak or strong?

3 Are the forces between the atoms in giant structures weak or strong?

4 Look at your results and decide which of the substances you have tested aremolecular and which have giant structures. Enter your conclusions in the table.

S Complete the table by deciding on the type of each substance, choosing from thefollowing:metal elementnon-metal elementcompound (metal + non-metal)compound (non-metal + non-metal).

6 Can you work out any rules for predicting the structures of substances?

7 Are there any exceptions to your rules?



Worksheet C5BIons on the move potassium manganate(vlI)

IICut out a strip of filter paper to fit on amicroscope slide. Draw a pencil line across themiddle.

IIMoisten the paper with a few drops of tapwater and place it on the slide. Attach crocodileclips, with leads, at each end. Support the slidehorizontally.

IIUse tweezers to place a small crystal ofpotassium manganate(vn) on the pencil line.

IIConnect the leads to a 20 V d.c. supply. Notewhich clip is positive and which is negative.

II Look for changes on the slide for 15 to 20minutes.

IIWhat is the effect of reversing the connections?

Ouestions

20V d.c.power supply

crystal

crocodile clip

1 What changes do you see during the experiment? Draw diagrams to show whathappens.

2 Potassium manganate(vn) consists of two types of ions: potassium ions, K +, andmanganate(vn) ions, Mn04 -. From the results of this experiment what can you sayabout the colours of these ions?

3 How can you explain the observations described in your answer to question 1?

4 What do you think happens to the colourless ion during the experiment?

5 What would you expect to see if you repeated the experiment with other colouredsalts such as copper(n) sulphate?



Worksheet C5CIons and electrolysis

Cut off the bottom of this sheet along the dotted line. Then cut out the ions, thecharge symbols and the heating arrow.

IIPlace the ions in the model container to show how you think they are arrangedin a solid.

111 Now place the heating arrow under the container and imagine that it gets hotenough for the solid to melt.

IIRearrange the ions to show how you picture them in a liquid.

B Now place the charge signs above the electrodes to show that the power packhas been switched on. What will happen to the ions?

IISuggest how chemical changes happen at the electrodes. Turn the ions over andwrite on the back a symbol to show what they turn into at the electrode .

.... .



Worksheet C5D [side 1]Lawrence Bragg and the start ofX-ray crystallographyThis worksheet is designed to help you study section C5.6 in your Chemistry book.You have here a copy of part of the text so that you can write on it. The pictures arenot included but you can look at them in the book.

Study guideIIRead the passage carefully. It describes two theories about the nature of X-rays

and gamma rays.

iii In one colour underline a sentence which clearly states one of these theories. Inthe same colour underline the name of any scientists who are said to believe inthe theory.

III In a second colour underline another sentence which states the second theoryand also the names of scientists who are said to believe in it.

II In a third colour underline a sentence which gives a clear account of LawrenceBragg's inspiration.

IIFind the paragraph in which Lawrence Bragg describes how his inspiration cameabout. Draw a box round the paragraph. Number the three ideas which cametogether in his mind.

IIFind a sentence which tells you what Bragg's law is about and label it 'law'. Findanother sentence which shows what Bragg could work out with his law and labelit 'use of Bragg's law'.

D Bragg father, Bragg son and Jenkinson each contributed in his own way to thedevelopment of X-ray crystallography. For each person find and label a sentencewhich states how he contributed to the new science. Label the sentences:'father', 'son' and 'Jenkinson'.

1m Make a summary of some of the main ideas in the passage by answering thesequestions:• What was Lawrence Bragg's inspiration?• What could Lawrence Bragg work out using his law?• What contribution did each of these people make to the development of X-rayspectroscopy: Bragg father, Bragg son, and Jenkinson?

How can we discover the structure of substances?It is only in the last seventy years that a way has been found to find the position ofthe atoms in a crystal. To do this, scientists use X-rays, which are waves of the samenature as light but with a wavelength that is ten thousand times shorter. SirLawrence Bragg was the first person to realize that X-rays could be used to find outthe structure of substances. His father, Sir William Bragg, invented the firstinstrument to be used to investigate crystal structure. Together they discovered thestructure of many substances and started the science of X-ray crystallography.

This is how Sir Lawrence Bragg described their work:'My interest in science started when I was at school, and I think the main reason

was that my chemistry teacher taught in an interesting way. I went to school inAustralia. I was born in Adelaide and my family lived there till we all came toEngland when I was eighteen years old.

'When we were in Adelaide, my father used to talk to me about his scientific ideas.He had gone to Adelaide as a young man to be Professor of Mathematics and

CONTINUED© Nuffield-Chelsea Curriculum Trust 1988.


h I; [ id ], '

4.:5

Physics at the University. He was so busy building up the courses in the physicslaboratory, and helping to develop the new University that he never thought of doingresearch for nearly twenty years. But when he was in his forties he was asked to givea lecture to the Australian Association for the Advancement of Science. He chose totalk about the exciting new discoveries which were being made in radioactivity.

'Preparing his lecture he began to wonder whether the explanations of the way therays from radium behaved were right. He decided to check some of the properties forhimself. So he got the University to buy some radium, and started experiments onalpha rays. They were brilliantly successful. Ernest Rutherford was tremendouslyinterested because they fitted in so well with his theory that radioactive decayresulted from the breakdown of the atoms of radioactive elements. At this timeRutherford was trying to convince doubting scientists that one element was changinginto another during radioactive processes. This idea did not fit with the existingtheory that atoms were unchangeable.

'In two or three years my father became world famous as a pioneer inradioactivity. In 1908 we all came home to England because my father was invited tobecome Professor of Physics at Leeds University. In England I went to TrinityCollege, Cambridge. I started with mathematics but after a year my father thought itwould be better if I switched over to physics. So that was how I became a physicist.

'My father went on to study the other radiations coming from radioactivesubstances. He was particularly interested in gamma rays, which, like X-rays, couldmake gases conduct electricity. He came to the conclusion that gamma rays andX-rays were not waves but more like a stream of little bullets. I remember the firsttime he told me of his ideas, just as we were boarding the old horse tram which randown the main street near our home.

'My father went on developing his theories and had scientific fights with thosepeople who believed in waves. So there was great excitement when, in 1912, aGerman scientist called von Laue published a paper with some beautiful photographswhich, he claimed, showed that X-rays were definitely waves. He obtained thesephotographs by sending a narrow beam of X-rays through a crystal, and placing aphotographic plate on the far side. When the plate was developed, it showed anumber of spots in a pattern of the same symmetry as the crystal. Von Laueexplained that the effect was caused by "diffraction" of waves by the regular structureof the crystal.

'My father and I read about von Laue's explanation while we were on summerholiday on the Yorkshire coast. I had just taken my degree at Cambridge and wasthen twenty-two. I, of course, was a warm believer in my father's theories and we triedto find a way of explaining von Laue's photographs by something other than waves.

'However, when I returned to Cambridge for the autumn term I became convincedthat von Laue was right to think that they were produced by waves. At the sametime, I had an inspiration which led me to believe that von Laue was on the wrongtrack when he tried to explain the peculiarities of his diffraction picture. He thoughtthat the odd results were due to a complex set of wavelengths coming from the X-raytube. I decided that the peculiarities were due to the way the atoms were arranged inthe crystal. If this were so, then X-rays could be used to find out the arrangement ofthe atoms.

'It is worth while describing this inspiration in some detail because it shows howscientific ideas often arise. They come because one hears about a piece of knowledgefrom one source, and happens to have a quite separate piece of knowledge fromanother source, and somehow the two just click together and there is a new idea. Inmy case, it was a kind of treble-chance.



'First J.J. Thomson lectured us about X-rays, and explained them as a wave-pulsecaused by the electrons hitting the target in the X-ray tube and being stoppedsuddenly. Second C.T.R. Wilson had given us a very stimulating lecture whichshowed that one could think of white light either as a series of quite irregular pulsesor a continuous range of wavelengths. Third at a meeting of my college's scientificsociety a member discussed a theory that in crystal structures the atoms were packedtogether like spheres with volumes proportional to the number of chemical bondsthey form. This theory proved in the end to be quite wrong, but it suggested somevery useful ideas. In science a wrong theory can be very valuable, and much betterthan no theory at all.

'Hearing this paper, 1 realized that the atoms in crystals were arranged in parallelsheets. Anyone thinking about crystal patterns would see this at once, but 1 hadnever thought about it before. So these three bits of knowledge were part of mybackground. When 1 was walking one day along the Backs at Cambridge - 1 canremember the place behind St John's College - suddenly the three bits came togetherwith a click in my mind. 1 suddenly realized that von Laue's spots were thereflections of the X-rays in the sheets of atoms in the crystals.

'Excited by my idea 1 did some experiments to get von Laue patterns ofalkali-metal chlorides. 1 was able to show that there was a simple law connecting thewavelength of the X-rays, the spacing of the atoms in the crystal and the angles atwhich the diffraction spots were obtained. 1 was able to use the law to work out thecrystal structure of several compounds.

'When 1 told my father about my results, he was of course very interested, and heat once started experiments to find out whether the rays which 1 had found to bereflected from crystal faces were in fact X-rays. When 1 wrote my paper 1 did notwant to take this for granted, so 1 called the paper "The diffraction of shortelectromagnetic waves". 1 avoided mentioning X-rays, having been very much teasedat Cambridge for upsetting my father's own theory!

'To make an accurate study of the waves, my father built what he called an X -rayspectrometer. It was a beautiful instrument. My father was very good at designingscientific apparatus and he had at Leeds a genius of an instrument maker namedJenkinson.

'My father's instrument proved invaluable for use on crystal structure. 1 was at thattime trying to interpret the X-ray photographs produced by a diamond, and wasquite bogged down. With my father's spectrometer it was possible to measure thereflections of the X-rays from the crystal planes, and this led at once to a solution.The diamond structure aroused a great deal of interest and had a strong influence inconvincing scientists of the value of X -ray crystallography.

'I had a grand time in the holidays. My father's interests were still mainly in X-rayspectra and he let me examine crystals with the X-ray spectrometer, and use hismeasurements to try to work out their structures. We worked furiously in 1913 and1914, going back in the evenings to the deserted university to get moremeasurements. It was like discovering a gold field with nuggets just lying there to bepicked up. One could not resist the temptation to pick up more and more, without arest. 1 was very lucky. If it had not been my father who developed the X-rayspectrometer, 1 should never have been able to work with it.'



Worksheet C6AMaking glass lead(lI) oxide

II•Measure the ingredients intoa sample tube.• Stopper the tube and shakewell to mix them.

Take care: the lead(n) oxide ispoisonous.

3.25 g lead(n) oxide1.75 g boric acid I0.25 9 zinc o~de !

mixture

cruciblepipe-clay triangle

iii • Tip the mixture into acrucible.• Place the crucible on a pipe-clay triangle and heat it with ahot flame.• Heat until the mixture ismolten and runny.

~stopper

tube

II• Quickly pour the glass onto aheatproof mat to form smallbeads.

II•Allow the glass beads tocool.• Then look at them carefully.

Results1 Keep a record of the changes you see as you make the glass.

2 Examine the glass once it has cooled down. How does it compare with the glassused to make test-tubes? Is it clear or cloudy? Is it coloured or colourless?

Further investigations3 Find out if the glass you have made is resistant to chemicals. Place small beads ofthe glass in test-tubes containing acids, alkalis and bleach and leave overnight. Dothese chemicals affect your glass more than the glass used to make test-tubes?

4 Investigate the effect of metal oxides on the colour of glass. Make glass as before,but this time add just a speck of one of these oxides: manganese(Iv) oxide, copper(n)oxide, or cobalt(n) oxide. (Start with the smallest possible amount of the oxide. It iseasy to add too much and just get very dark glass.)



Worksheet C6BGlass working

Remember:• Hot glass takes a long time to cool.• Turn the glass round and round (not backwards and forwards) in the flame whenyou heat it.• Fire polish the cut ends of rod or tube.• Clear up any scraps of broken glass immediately.

Glass stirring rodIIHeat one end of a length of glass rod

by rotating it in a hot flame.

1m When the glass has softened, press theend down firmly onto a heatproofmat.

II Set aside the rod to cool.

II Repeat the process for the other end.

Dropping pipetteIIHeat one end of a length of glass

tubing by rotating it in a hot flame.

1m When the glass has softened, press thehot end down onto a heatproof matto flatten it.

IISet aside the tube to cool.

IINow rotate the other end in a hotflame. Continue until the glass beginsto close in and forms a small hole.

II Fire polish both ends of a length ofglass tube.

1m Set aside to cool.

IIUsing a burner with a flamespreader (or a batswing burner),heat the tube towards one end,rotating it in the flame.

IIWhen the glass is soft, bend itthrough a right-angle. Then lay theglass on a heatproof mat to makesure that it is flat.

Right-angle delivery tube L!..-"" Glass bulbII Fire polish one end of a length of

glass tube.

1m Then set it aside to cool.

IIRotate the other end of the tube ina hot flame. Continue heating andturning the tube until the glass hascollapsed in on itself and sealed theend.

IIGet the sealed end as hot aspossible. Remove the glass fromthe flame. Blow down the polishedend until a small bulb forms.



Worksheet C6CFloat glass

Study guideGlass is made in a furnace. The problem is to shape the hot, molten glass into sheets.The following sentences describe the float glass method of solving this problem. Thesentences have been jumbled up. Cut up this piece of paper to separate the sentences.Then arrange the sentences in an order which seems to make sense to you.

A The sheet of glass is then allowed to cool as it continues across the bath of tinuntil at about 600°C it is hard enough to be lifted onto rollers withoutdamaging the underside.

B This is called annealing.

C The glass leaves the furnace at 1500 °C and floats along the surface of a bath ofmolten tin.

D When making flat glass it is difficult to form the hot glass into sheets which areuniform in thickness, smooth and shiny.

E Finally the glass sheet is cut and stacked ready for distribution to customers.

F The glass is kept at a high enough temperature on the molten metal for longenough for the surface to become flat and parallel.

G A new method for making sheet glass was invented by Pilkington Brothers andintroduced in 1959.

H Next the continuous sheet of glass moves through an oven where it cools slowlyunder controlled conditions.



Worksheet C7AProperties of metals

Here are some of the useful properties of metals.Fill in the table, deciding for yourself whether the properties listed are useful. Also

give at least one example of the way in which each property is put to use.

Property N arne three metals which Name one metal which Is the property useful?possess this property does not possess this Give one example

property (if any)

Metals are solid

Metals are hard

Metals are strong

Metals are shiny

Metals bend

Metals are tough

Metals feel cold

Metals conductelectricity

Metals are dense

Some metalsare magnetic

Metals make a ringingnoise when struck

Metals expandon heating

Metals react withthe air

Metals reactwith acids



Worksheet C7B [side 1]Analysing an alloy •~ ~ [iJ••••

concentrated nitric acid concentrated nitric acid solventconcentrated ammonia locating agent

The metals in an alloy can be identified by dissolving a sample in a mixture ofconcentrated acids. This converts the metal atoms to metal ions which dissolve. Themetal ions can then be separated and identified by chromatography. Your teacherwill help you prepare the solution you need for the analysis.

I

chromatographypaper

jar with lid ----<I

,--l__ ..t~--1 cm depth/ " of solvent

small spotsof solutionsof knownmetal ions

small spot ofsample solution

II• Add solvent to the jar toa depth of 1 em. Cover with agreased lid.• Let it stand for a while sothat the air in the jar becomessaturated with the vapour of thesolvent.

II• Draw a pencil line across the paper 2 em from thebottom. Make six pencil dots along the line. Label each dot,one for each of the five known ions and one for the solutionof the alloy.• Apply one spot of each solution at its labelled point onthe line, using a separate, fine tube for each one.

II• Allow the spots to dry.• Then fold the paper into acylinder and fasten the sides withplastic clips.• Stand the paper in the jar,making sure that it does nottouch the sides. Replace thelid.

II•Wait until the solvent has risen near to the top of thepaper.• Remove the paper, using tweezers, and allow it to dry.Now open out the paper and use tweezers to draw it througha solution of the locating agent in a large watchglass, ordish.• Finally hold the paper over a beaker of concentratedammonia solution in a fume cupboard until coloured spotsappear.

large watchglass ordish

tweezers

chromatographypaper

chromatographypaper coiled into acylinder andfastened withplastic clips

sample spotsabove the levelof the solvent



]

Ouestions1 Why is the air in the jar saturated with the vapour of the solvent before the paperis put into the jar?

2 How is the alloy treated to get a solution of the metal ions?

3 Why is the chromatography paper marked in pencil and not in ink?

4 Why must the spots of the sample solutions be kept small?

5 No locating agent is needed when chromatography is used to analyse food colours,or the colours in inks and grass. Why is a locating agent needed in this experiment?

Results6 Make a drawing of your chromatogram to show the appearance and position ofthe spots after they have been shown up by the locating agent.

7 Which metals are present in the alloy you have analysed?



Worksheet C8A [side 1]Polymerization

Warning:The chemicals used to make plastics are very reactive - they will react with you if youare not careful. Wear gloves to protect your hands.

Part 1: Making nylon

5mlofsolutionl: nhexanedioyldichloride in a denseorganic solvent l

hexanedioyl dichlorideorganic solventdiaminohexane

oglass rod

5 ml of solution 2:diaminohexanein water

IIVery carefully pour solution 2 onto solution 1.The organic solvent does not mix with water.So you should end up with two layers in thebeaker.

IIUse tweezers to pick up the film of nylonwhich forms where the two layers meet. Windthe thread round a glass rod. Then keepturning the glass rod to draw out more andmore nylon from the beaker. Do not touch thenylon with your bare hands.

Questions

1 What changes can you detect which suggest that there is a reaction between thechemicals in the two solutions?

2 Why does the nylon form at the boundary between the two layers?

3 What does the nylon look like? Is it strong or weak when made in this way?

4 Why does the nylon thread stop forming after a while?

_______________________________ CONTINUED



?].L

methanal dilute sulphuric acid

Part 2: Making a plastic from urea and methanalCarry out this experiment in a fume cupboard.

disposablecontainer,

5 9 ofUre~" ",,2"<0\ )

glass rod ------<I

n10mlofmethanal inwater

solution ofurea inmethanal

5mlofdilutesulphuricacid

II Pour the methanal solution into the disposablecontainer. Then stir to dissolve the urea.

111 Add 5 ml of dilute sulphuric acid. Stir well.Watch what happens for the next 5 to 10minutes.

Questions

5 What changes can you detect which suggest that there is a reaction between thechemicals?

6 The acid is added as a catalyst for the reaction. What is the purpose of a catalyst?

7 Describe the appearance of the plastic you have made.

8 Both the experiments described on this sheet involve condensation polymerization.What is meant by the term 'condensation polymerization'?

© Nuffield--Chelsea Curriculum Trust 1988.


Worksheet C8B [side 1]The label at the back -a look at clothing fibresPractically all clothes are made from fibres. But many different kinds of fibres areused to make clothes - cotton, polyester, wool and nylon are just a few. In this unityou will be using the labels in clothes to find out the fibres in them. Then you will beanswering questions about the different fibres you come across.

/St1llkltoJJt1 ]MADE IN THE U.K ]

TOUR DE POITRINE

71cm

brand name

washinginstructions

country it wasmade in

size

] fibres

]

TO FITCHEST

28 in

CA01295

\~/aHOT

TO FIT HEIGHTHAUTEUR

140CII 55 in

67% COTTON/COTON33% POLYESTER

A

Figure 1A wide range of fibres is represented in the clothes in a department store like this

Figure 2A typical clothing label

Part 1: Looking at clothing labelsThis is best done at home. Look at a range of different garments - pullovers, dresses,trousers, shirts, blouses, skirts, night wear, jackets and so on. Each garment youchoose must have a label in it showing what it is made from. Figure 2 shows atypical label.

IIDraw up a table like figure 3. An example has been filled in to show you what todo.

Garment Fibres it contains Country it was made in

Shirt 670(0 cotton '3g~ payester U.K.

Figure 3

II Enter the details for each garment in the table. You should include at least tendifferent garments in your survey.

IIMany garments have a mixture of different fibres. Give the percentage of eachfibre.

_______________________________ CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 405. © in this format Nuffield-Chelsea Curriculum Trust 1988.


he

Part 2: Which are the most popular fibres?Fibres Factsheet 1 lists the commonest fibres, and gives some of the other names theyare known by.

IIDraw up a table like figure 4.

II First enter your own results, in the second column. Count up the number ofgarments in which each fibre is present. It does not matter whether the fibre ispart of a mixture or the only one present.

IINow collect the combined results of the whole class, and put them in the thirdcolumn.

Name of fibre N umber of garments Number of garmentscontaining the fibre containing the fibre in thein your survey whole class combined

Cotton

Wool

Silk

Viscose

Acetate

Triacetate

Nylon

Polyester

Acrylic

All other fibres

Figure 4

CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SAliS Unit No. 405. © in this format Nuffield-Chelsea Curriculum Trust 1988.


Part 3: Ouestions and activities1 Present the combined results for the whole class in a way that makes it easy to

see which fibres are most popular. For example, you might draw a bar chart or a piediagram. Try to make your diagram as clear and attractive as you can.

2 Apart from the UK (or Britain), which countries manufacture the garments inyour survey? (You could collect these results from the whole class, and present themon a bar chart or other diagram.)

Study Fibres Faetsheet 1 before you answer questions 3 to 7.

3 Why are silk garments uncommon?

4 In tropical countries, cotton is the most common fibre. Give one reason why thismight be.

5 Choose one garment from your survey that needs to be particularly hard-wearing.What fibre is it made from? Why?

6 Choose one garment from your survey that needs to be particularly warm. Whatfibre is it made from? Why?

7 Choose two other garments from your survey. What fibres are they made from?In each case, say why you think these particular fibres where chosen.

Study Fibres Faetsheet 2 before you answer questions 8 and 9.

8 Explain the difference between a synthetic fibre and a regenerated fibre.

9 Which was the most popular natural fibre in the class survey? Which was themost popular regenerated fibre? Which was the most popular synthetic fibre?

Study Fibres Faetsheet 3 before you answer questions 10 to 14.

10 Judging from chemical structures, which artificial fibre might you expect to haveproperties similar to cotton?

11 Suggest one reason why acetate is a low-price fibre.

12 Silk and wool are both protein fibres, yet their properties are very different. Whatdifferences between their protein chains might be responsible for their differentproperties?

13 Some fibres are described as 'cellulosic' fibres. Which fibres on the factsheet arecellulosic?

14 Regenerated fibres have been used for about a hundred years, but synthetic fibreshave only been in use for about fifty years. Suggest a reason for the difference.



r Iin

Fibres Factsheet 1: Properties of fibres

Name of fibre Other names used Price range Water Durabilityb Other advantages andabsorbencya disadvantages

Cotton medium high medium Feels comfortable,absorbs perspiration

Wool high high high Feels comfortable andlooks attractive.Very warm when knitted

Silk very high high high Looks and feels attractive

Viscose Rayon, Sarille, low medium lowModal

Acetate Dice! low medium low

Triacetate Trice! medium medium low

Nylon Bri-nylon, polyamide medium low high Stretches, dries quickly,strong

Polyester Terylene medium low high

Acrylic Courtelle, Acrilan, medium low medium Warm when knittedModacrylic, Orlon

aHigh water absorbency means the fibre attracts water. It can absorb quite a lot of water before it feels wet.bHigh durability means the fibre is hard-wearing.



Fibres Faetsheet 2: What are fibres made from?Some fibres come from natural sources - plants or animals. Other fibres are artificial.Artificial fibres are of two sorts. Some are made by changing and improving naturalfibres. These are called regenerated fibres. Others are completely artificial, made fromnon-living materials, usually oil. These are called synthetic fibres.

Figure 1 shows the main types of fibres.

______ -« woolanimal .

natural--< silk

<cotton

plant ------~.

linen

nylon

synthetic -------« polyester-< acrylicartificial

viscose

regenerated -----« a~etate

tnacetate

Figure 1The main types of fibres

FIBRES

All fibres, whether artificial or natural, are polymers. That means they containmolecules which are long chains. These long molecular chains are made by joiningtogether hundreds or thousands of smaller units, called monomers. For example,cotton is made of cellulose. Cellulose is a natural polymer made by joining togetherlots of glucose molecules. Glucose is the monomer of cellulose. The structure ofcellulose is shown in Faetsheet 3.

Natural fibres like cotton and wool are already in the form of long fibres. Artificialfibres have to be made in bulk as a thick liquid. The liquid is then extruded intofibres. This means it is forced through small holes, like toothpaste being forced out ofa tube (figure 2).

warm air to dry the fibres

Figure 2Extruding artificial fibres

thick liquid

fibres

Fibres Faetsheet 3 gives more details about what the different fibres are made from.



-•..eo:sQ.,

'-Q~•..=-(oJ=•..-rJJ.

'0o~

CI).•...C'\l.....CI)u<

:::co

J):::c

0..CI)CI)

,.Q00

;>.,.0

CI)"'0

C'\l

S

:::c

~o

do..........oU

•..~eQ=

~

.:a.~

.~

M....,Q)Q).cen....,Co)ca

•••••enE-=.-

•••••

enQ)•..-=;....,=Q-=caCQ.::;cae•...ec.-



Worksheet e8CPolymers all about us

Picture Useful properties Limitations of polymers Type of polymerof polymers shown shown in the picture (if known)in the picture



Worksheet C8D [side 1]A key to identify plastics

WarningsSome thermoplastics can melt and drip when heated.Many plastics give off irritating fumes when hot.Some fumes are toxic.

some plastics some plastics fumes fromwhen burnt burning plastics

The key provided will only work for the limited range of plastics listed. Plastics maybe 'disguised' by the presence of dyes, pigments, fillers and plasticizers.

Procedure for using the keyYou are asked to find out which plastics have been used to make the samplesprovided. Follow the key on side 2 to work out which plastic you are testing.Here are some details about the tests mentioned in the key.

Hot nail test

Do this test in a fume cupboard. Hold the nail in a flame with tongs, then press itagainst the sample of plastic. You are looking to see how easily the plastic melts.(You are not trying to make the sample catch fire when doing this test.)

Float test

First wash the sample with detergent and rinse with water. This helps to prevent airbubbles affecting the test. Let go of the sample below the surface of water in a bowlor trough. Does it float or sink?

Burning test

You must do this test in a fume cupboard, as many plastics produce toxic fumes. Donot use a Bunsen burner.Use only a small piece of plastic and hold it in tongs.Work above a large tin lid over a heatproof mat.Heat the plastic using the small flame of a wood splint or a spirit lamp.Does the plastic catch fire easily and keep burning with a yellow flame?If the plastic does not catch fire easily, test the fumes with moist blue litmus paper.

ResultsRecord your results in a table like this.

Object from which the N arne of the plastic Is it thermosetting orplastic sample was cut thermosoftening?

_______________________________ CONTINUED



he [si e ]00 !I

Does it melt if touchedwith a hot nail?

polypropylene

Yes

~

No~

polythenelow density poly(ethene) film feels wa~;high density poly(ethene) film makes alouder rustling sound when crushed

If you snip the edge,will it then tear

smoothly withoutstretching?

Yes ~

Does it catch fire easilywhen held in a small

flame, and keep burningwith a yellow flame?

Does it float in water?

No

Yes

Yes

\phenol-

formaldehyde

Start

!

No

!

No

urea-formaldehyde

If heated until it fumes(but is not burning), doesit give off fumes which

turn blue litmus red?

No

!nylon

the fumes smellof burnt hair

JNo

Yes

~pvc

Does it burn witha smoky flame?

No Yes

~acrylic

froths as it burns, especiallyjust after the flame has been blown out

Does it give a metallicring if tapped with

a pencil?

No

!polyester

odour of burnt jam as it burns

Yes

"'-polystyrenesooty smuts as it burns



Worksheet e9A [side 1]Investigating colloids

This is a series of experiments which you can do in any order.

Light-scattering

Procedure

You will find that there are several labelled tubes in a rack.

IIHold each tube in turn in a bright light beam.

III Look to see if you can see any sign of light-scattering. (Ignore the scattering byany large dust particles which may be floating in the solutions.)

Results

1 Record your results like this.

Substance in the water Do the contents of the Is it a sol, gel, ortube scatter light? solution?

Questions

2 Do colloids scatter light equally in all directions?3 Can you see any evidence that some colours in white light are scattered more thanothers?

Milk under the microscope

Procedure

IIUse a glass rod to put one drop of milk on a microscope slide.

III Lower a coverslip onto the milk without trapping any air bubbles.

\II Examine the milk under the microscope, first with medium power, then with high

power.

Results

1 Draw diagrams of what you see and label the fat globules in your diagrams.2 Are the fat globules still, or are they moving?

Questions

3 What name is given to the movement of small particles suspended in a liquid?4 What causes the movement?



1J

Types of emulsion

Procedure

A mixture of dyes is used in this experiment. The blue dye is soluble in water. Theorange dye is soluble in fat. If the dye mixture is sprinkled onto an emulsion thecontinuous phase takes up the dye which dissolves in it. So an oil-in-water emulsioncolours blue. A water-in-oil emulsion colours orange.

a The emulsions in the labelled watchglasses have been sprinkled with the dyemixture.

III Note the colour which appears on the surface of each one. (The dyes will stainyour skin, so be careful not to touch them.)

Results

Emulsion tested Colour which appears Is the emulsionon the surface of the oil-in-water oremulsion water-in-oil?

The effect of ions on a colloid

Procedure

a Shake about 0.1 g of titanium dioxide with 20 ml distilled water in a stopperedboiling-tube. Titanium dioxide is the pigment in white paint.

III Pour equal amounts of the mixture from a into four separate test-tubes.• Number the tubes 1 to 4.• To tube 1 add 5 m! of water.• To tube 2 add 5 ml of sodium chloride solution.• To tube 3 add 5 ml of magnesium sulphate solution.• To tube 4 add 5 ml of alum solution.

II Stopper the tubes. Then shake them to mix the contents and put them in a test-tube rack.

IIWatch what happens in the tubes for about 30 minutes.

Results

1 Look for signs that the particles of titanium dioxide are coagulating and settling.Describe any changes you see in each tube.

Ouestions

2 Which of the added solutions cause changes in the titanium dioxide dispersion?

3 Look up the symbols and charges of these metal ions: sodium, magnesium andaluminium. Does the size of the charge on the metal ions seem to affect the results?(Remember that there is evidence that the titanium dioxide particles are negativelycharged.)



Dialysis

] I'~I•••••sodium hydroxide Benedict's solution

copper(n) sulphate solution

The Visking tubing containing milkhas been standing in the beaker ofwater for over an hour. A sampleof the milk is available in adropper bottle. water milk

Procedure

IICarry out test A for sugars and test B for protein. Test both the milk in thedropper bottle and the water outside the Visking tubing.

II Find out whether milk can pass through filter paper.

Test A: For sugar• Mix 1 ml of the liquid to be tested with 3 ml of Benedict's solution in a boiling-tube.• Warm the mixture with a small flame. An orange colour indicates the presence ofsugar.

Test B: For protein• Take 2 ml of the liquid to be tested and add 3 ml of sodium hydroxide solution ina test-tube.• Shake, then add a drop or two of copper(n) sulphate solution. A purple or violetcolour indicates the presence of protein.

Questions

1 The sugar in milk which reacts with Benedict's solution is called lactose. Canlactose pass through Visking tubing?

2 The protein in milk is called casein. Can casein pass through Visking tubing?

3 The fat in milk makes it look white. Does any of the fat pass through Viskingtubing?

4 Which of these parts of milk can pass through filter paper: the sugar, the protein,the fat?

5 Which of these parts of milk are colloidal and which are in solution: the sugar, theprotein, the fat?



Worksheet C9BSurface tension

You will be given a special detergent solution which can be used to make films andbubbles which last a long time. Start with the experiments suggested on this sheet.Then try your own investigations.

Procedure film of detergent solution wire slider

IIForm a film on the frameand slider by dipping it intothe trough of detergentsolution.

III What happens as you gently~

wire frame---< L ~re~pull on the thread and thenlet go?

ProcedureII Form a film on the circular

frame by dipping it into thetrough of detergent solution.

III What happens as you use apencil, or other pointedobject, to break the filmbetween the threads?

~read

wire frame

ProcedureII First predict what you think will happen when

the wire cube is dipped into the detergentsolution and then removed.

III Now try it. What happens?

II Try the same thing with other shapes if they areavailable.

© Nuffield-Chelsea CUrriculum Trust 1988.

wire holder

wire cube


Worksheet e9CMaking a cosmetic cream

In this experiment you will make a cosmetic cream which can be used as afoundation for greasepaint in the theatre. The emulsifier is potassium stearate whichis formed as the ingredients are mixed.

@)~potassium hydroxide

stirring thermometer159 of stearic acid

8 g glycerol76 ml distilled water

+ 0.7 9 potassium hydroxide(from your teacherl

IIWarm and stir the stearic acid until thetemperature is a little above 75°C.

IIRemove both beakers from the burners. Pourthe solution made in b into the molten stearicacid from a, stirring as you do so. Keepstirring until the mixture has cooled to below50°C.

Results

II In a separate beaker, warm and stir themixture of distilled water, glycerol andpotassium hydroxide until the solid hasdissolved and the temperature is 75 DC.

IIAdd a drop or two of perfume and a minuteamount of preservative. Stir well, then transferthe product to a labelled jar.

1 Describe the appearance and consistency of the cream when cold. How does itcompare with the starting materials?2 Test your product by rubbing a little into one area of the skin on your hand.Apply greasepaint to both treated and untreated parts of your skin. Compare theease with which you can remove the greasepaint from the two areas using cottonwool.



Worksheet Cl0AComparing detergents

A detergent is something which cleans. In this experiment you will try washing dirtycloth with water, and compare the results of using a soap detergent and a soapless detergent.

cloth

Part B: Washing the clothIIKeep the clean control sample for comparison.

Do not wash it.

Part A: Preparing the dirty clothlEI Take four pieces of fabric of the same

material. Cut off one corner of each sothat you can tell where the stains wereafter washing the samples. Number thesamples with a marking pen.

IIKeep one piece of cloth as a clean,control sample. Dirty the other threesamples to a fixed pattern, such as theone shown in the diagram. trough or bowl

wooden stickfor strirring

hot water

Try to apply about the same quantity ofdirt to each sample.

Draw a diagram to show which stainsyou used and where you put them.

IIWash one of the dirty samples in hot water only.

IIWash another dirty sample in hot water with soap.

IIWash the third dirty sample in hot water with asoapless detergent powder.• Use the quantities of washing powderrecommended on the packet. Heat the water tothe temperature suggested for the type of clothyou are usmg.• Wash each cloth sample for five minutes.Rinse twice with cold water. Squeeze to removemost of the water, then leave to dry.

d~~t' "", :

II

Results1 Compare the three samples you have washed with the control sample. Use a5-point scale to compare the results for each stain. If the test sample is as clean asthe control, rate it as 5. If the dirt has hardly been affected rate it 1. Record yourresults in a table like this.

Dirt Hot water only Hot water with soap Hot water withsoapless detergent

OilClayCharcoalLipstickFatDust

2 Write a report summarizing your findings, and compare your results with othergroups which have tried washing other types of cloth.



Worksheet Cl DBWhich is the best way ofsoften ing water?ProcedureFirst use the test for hardness described below to compare the sample of hard waterwith distilled water (which is soft).

Then tryout the various methods of softening water on samples of the hard water.

Testing for hardness

• Use a measuring cylinder to take a 10-ml sample of the water in a test-tube. Addsoap solution drop by drop from a pipette. Stopper and shake the tube each timeyou add a drop of soap solution. Count the drops as you add them.• Continue until you get a mass of bubbles at least 0.5 cm deep which remains afterthe water has been standing for a minute.• Also note any changes in the appearance of the solution.

Methods of softening water

BoilingTake 40 ml of the hard water in a beaker and boil it for a few minutes. Allow it tocool. Then test for hardness on a 10-ml sample.

CalgonStir 0.25 g of Calgon into 75 ml of the hard water in a beaker. Test a lO-ml samplefor hardness. Now heat the rest of the water which has been treated with Calgon, tothe temperature of a hot bath. Test another 10-ml sample for hardness.

Bath saltsStir 0.25 g of bath salts into 75 ml of the hard water in a beaker. Test a 10-ml samplefor hardness.

Ion exchangePour some of the hard water into the ion exchange column provided. Run off 10 mlinto a measuring cylinder. Then test for hardness.

Results

Water sample tested Observations made Number of drops of How hard is theduring the softening soap solution needed water sample?process for a good lather

Untreated hard waterDistilled waterBoiled waterWater treated with Calgon (cold)Water treated with Calgon (hot)Water treated with bath saltsWater treated by ion exchange

Ouestions1 Which is the most effective method of softening water?2 How do the methods compare in terms of cost and convenience?

3 Overall, which do you think is the best method of water softening for use at home?



Worksheet ellA [side 1]Dyeing with indigo

~

~sodium hydroxide sodium dithionite

Indigo is a vat dye. This means that it has to be turned into a soluble form before itcan be used to dye. The cloth is then soaked in the solution. When the dye turnsback to its coloured insoluble form the fabric is permanently dyed.

Follow the instructions to dye a piece of cotton large enough to be cut into threepieces after dyeing. One piece is for your records, one piece to test for light fastness,and the third to test for fastness to washing.

Part 1

0.2 9 indigo0.5 9 sodium hydroxide ~1.0 9 sodium dithionite

~

200 ml water

cmtoncl~ JcP

solution of dye

IIAdd measured quantities of the solids to 200 mlwater. Stir and heat until the solution is yellowand clear.

IIAdd cloth to the dye solution. Stir and simmerthe solution for about ten minutes.

IIRemove the cloth from the dye and wash itthoroughly under running water. (Keep the dyesolution for part 2.)

Results

IISpread the cloth on a paper towel, or otherabsorbent paper and leave to dry.

1 Describe the appearance of the dyebath as it is made and used in steps a and b.

2 What happens to the cloth during steps c and d?



Part 2

~

~sodium hydroxidehydrogen peroxide

sodium dithionitedilute hydrochloric acid

II Immerse 5 small pieces of untreated cotton inthe hot dyebath used in part 1.

III After a few minutes pick out the pieces of clothone at a time. Quickly transfer them to separateboiling-tubes as shown here on the right.

IIObserve the rate at which the cloth turns bluein each tube.

water dilutehydrochloricacid

sulphurdioxidesolution

acidpotassiumdichromate

hydrogenperoxide

Ouestion

3 Which of the solutions in the test-tubes seem to have the same effect as leaving thedyed cloth exposed to the air?

Further investigations4 Devise and carry out experiments to test the fastness of your dyed samples.• How fast is the colour when washed?• How fast is the colour when exposed to sunlight? (It will take 2 to 3 weeks to getresults, depending on how sunny the weather is.)

(You may decide to do the fastness testing when you have completed all the dyeingexperiments and can test all the samples at the same time.)

© Nuffield-Chelsea CurriculumTrust 1988.


Worksheet ell B [side 1]Mordant dyeing

In this experiment you will use alizarin which used to be obtained from the madderplant but which is now made synthetically. You will dye cotton cloth with andwithout alum as a mordant. You may also have time to see what happens with othermordants.

Each time use a piece of cotton large enough to be cut into three pieces. One pieceyou keep as a record of your results, the second piece is to test for light fastness andthe third to test for fastness to washing.

Either wear gloves, or handle the fabric with (clean) tongs.

Part 1Dye untreated cloth, as follows.

IlIllI

II Immerse untreated cottoncloth in a hot solution of thedye for a few minutes.

IIThen remove the cloth, rinsethoroughly in water and blotdry.

untreated r:L,cotton \J ~ stir for a few minutes

hot alizarinsolution (0.' 9

JlIlIIlI in 100miwater at

about 70 °CI

---- CONTINUED© Nuffield-Chelsea Curriculum Trust 1988.


Part 2

he 11 ide ]dilute ammonia solution

Now mordant another untreated cloth sample with alum (steps a and b) and then dyein alizarin (step c).

IIDye the mordanted samples of cloth asin part 1. Rinse with water and blot dryas before.

50 ml diluteammoniasolution

II Immerse the clothsample in ammoniasolution in a fumecupboard for 2 to 3minutes.

~

ottonfromstep a

squeeze out thealum solutionbefore going on

~~

50 ml of asolutionof alum

IINow immerse thecloth in a solution ofalum for 2 to 3minutes.

b1\¢> ~:f~i~utes

clOth;:)step b hot alizarin

dye solution(as in part 1)

IIIf you have time, repeat steps a, band c, using a different mordant in step b. Possible mordants includeiron(n) sulphate, magnesium sulphate and tin(n) chloride.

Results1 Make a neat display of the results of this experiment.

Ouestions2 Do your results support the idea that a mordant helps to make a dye stick tocloth?

3 Do your results show that the choice of mordant affects the colour of the dye?

Further investigations4 Devise and carry out experiments to test the fastness of your dyed samples.• How fast are the colours when washed?• How fast are the colours when exposed to sunlight? (It will take 2 to 3 weeks toget results, depending on how sunny the weather is.)

(You may decide to do the fastness testing when you have completed all the dyeingexperiments and can test all samples at the same time.)



Worksheet ell CDyeing with a reactive dye

Procion yellow is a reactive dye which dyes cotton in the cold, under alkalineconditions. It reacts with cellulose in cotton. The dye molecules become linked to thecellulose by a strong chemical bond.

ProcedureDye a piece of cotton which is large enough to be cut into three pieces. One piece isfor your records, another piece for testing light fastness, and the third piece fortesting fastness to washing.

IIAdd the paste to 200 mlwater at 80°C.

hot solutionfram step b

cotton

r\J

II Spread the cotton on absorbentpaper and blot dry.

IIAdd 14 g salt to the solution madein step b and stir to dissolve it.Cool to below 40°C. When cold,immerse the cotton in the solutionfor 3 minutes.

200mlwater atBODe

"JIIID11[[111

pastefram~step a I +

IIRinse the dyed cottonthoroughly in cold water.

~ stir with a glassrad

1 g Pracionyellow with1mlcold water~~~==J

I

3 g sodiumcarbonate

dissolved inn5-10 mlwater

L\J.

IIAdd sodium carbonatesolution and stir well.Leave the cloth in thedye for 10 minutes.

IIMake a paste of thedyestuff with 1 ml coldwater.

Ouestions1 How does Pro cion yellow compare with natural dyes such as alizarin or indigo?Compare the depth of colour and brightness.2 Devise and carry out experiments to test the fastness of your dyed samples. Howfast are the colours when washed? How fast are the colours when exposed tosunlight?3 What evidence is there from your observations that the bond between the Prociondye and the cotton is stronger than the bond between alizarin and the cloth?



Worksheet e12AHow much gastric juice does'bicarb' neutralize?Some antacid tablets contain 'sodium bicarbonate' ('bicarb' for short). The modernchemical name for the compound is sodium hydrogencarbonate, NaHC03• A tabletmay contain 150 to 200 mg of the compound. Gastric juice is acidic because itcontains hydrochloric acid.

In this experiment, you will measure out some sodium hydrogencarbonate andthen find out how much hydrochloric acid it will neutralize. You will be given dilutehydrochloric acid with about the same concentration as gastric juice.

dilute hydrochloric acid

IIWeigh an emptyflask accurately.Then add between0.15 g and 0.20 gof sodiumhydrogencarbonateand weigh againaccurately.

sodiumhydrogen carbonate

I

IIDissolve thesolid in about15 ml distilledwater. Add2 drops of theindicator.

weighed sampleof 'bicarb' in15Qf screened

methylorangeindicator

IIFill the burettewith acid asshown by yourteacher. Checkthat there are noair bubbles inthe jet. Removethe funnel.Record the acidlevel.

Results

dilute ,,/hydrochloric acid ~

burette

smallfunnel

IIAdd acid from the burette.Swirl the flask to mix theacid with the solution ofthe antacid. Continue addingacid drop by drop untilthe indicator changes fromgreen to a grey or faintlypurple colour. Read theburette again and calculatethe volume of acid added.

1 Record your results like this.

Mass of empty flask = __ g

Mass of flask + 'bicarb' = __ g

Mass of 'bicarb' used = __ g

Summary

2nd burette reading1st burette reading

Volume of acid added/ml

2 The experiment shows that __ ml of gastric juice is neutralized by about__ mg of 'bicarb'.

Question3 How much gastric juice would be neutralized by an antacid tablet containing200 mg of 'bicarb'?



Worksheet e12S [side 1]Analysis of a magnesia tablet dilute hydrochloric acid

The active ingredient in the tablets to be analysed is magnesium hydroxide. This isan antacid which neutralizes excess hydrochloric acid in the stomach.

Mg(OH)2(s) + 2HCI(aq) ~ MgCI2(aq) + 2H20(l)

The same reaction can be used to analyse magnesia tablets if the concentration of thehydrochloric acid is known.

distilledwater

glassrod

stirc::=:>

iii Repeat steps a to f tocheck the accuracy of yourmeasurements.

IIUse a glass rod to breakup the tablet in the acid.Then rinse the rod withdistilled water so that thewashings all run back intothe flask.

IIFinally read the buretteagain and record yourmeasurement. Calculate thevolume of acid needed toneutralize the antacid inthe tablet.

burette

dilutehydrochloric acid(concentration known)

Now continueaddingacid fromthe burettedrop bydrop. Swirlthe flask wellafter eachaddition. Goon until theindicatorchangesto a grey or faintly purplecolour.

Read theburette andrecord theacid level.Then addabout 15 mlof the acidto the tabletin the flask.

tablet2~\'-r--~~- I

[L I ".C,' I" I

II'SkU

~l screenedmethyl~ ~;:~~:or

IIAdd two drops of theindicator. This will staygreen, showing that in stepb you added enough acidto break up the tablet butnot enough to neutralizeall the magnesiumhydroxide.

III Weigh a magnesia tabletand then put it into aconical flask.

ResultsRecord your results like this.

Mass of the first tablet =--g

Mass of the second tablet = __ g

First experiment Repeat experiment


Volume of acid added in ml

-------- CONTINUED© Nuffield-Chelsea Curriculum Trust 1988.


he 1 [si e ]IJ$

I

Calculations

1 What volume of the hydrochloric acid solution is needed to neutralize one tablet?

Work out, from your table of burette readings, the average volume of thehydrochloric acid solution needed to neutralize the magnesium hydroxide in onetablet.

2 What is the mass of magnesium hydroxide in one tablet?

The concentration of the acid has been measured.It is known that 1 ml of the hydrochloric acid reacts with x mg of magnesiumhydroxide. (You will be told the value of x.)Use this information, and your answer in step 1, to work out the number ofmilligrams (mg) of magnesium hydroxide in a tablet.

3 What is the mass of a tablet in milligrams?

You have measured the mass of the tablet in grams (g). Convert this value tomilligrams (mg).(1 g = 1000 mg)

4 What is the mass of neutral material in one tablet?

The tablet consists of magnesium hydroxide held together with a neutral materialsuch as starch.Use your answers to steps 2 and 3 to work out the mass of neutral material in atablet.

5 Conclusion

Write a conclusion summarizing the results of your analysis.



Calculations

1 What amount of the hydrochloric acid is needed to neutralize one tablet?

a Work out, from your table of burette readings, the average volume of hydrochloricacid solution needed to neutralize one tablet.Give the volume in litres (L).

b Work out the amount (mol) of hydrochloric acid needed, using this formula:

• Amount of substance = Volume x Concentration(mol) (L) (moljL)

You will be told the concentration of the hydrochloric acid.

2 What is the mass of magnesium hydroxide in one tablet?

a Look at the equation on side 1 of this worksheet. You can see that 1 mol ofmagnesium hydroxide reacts with 2 mol of hydrochloric acid.From your answer to step 1 of this calculation, work out the amount (mol) ofmagnesium hydroxide in one tablet.

b Now work out the mass of magnesium hydroxide in one tablet.

• Mass of substance = Amount of substance x Molar mass(g) (mol) (g/mol)

Give your answer in milligrams. (1 g = 1000 mg)

3 What is the mass of a tablet in milligrams?

You have measured the mass of the tablet in grams (g). Convert this value tomilligrams.

4 What is the mass of neutral material in one tablet?

The tablet consists of magnesium hydroxide held together with a neutral materialsuch as starch.Use your answers to steps 2 and 3 of this calculation to work out the mass of neutralmaterial in a tablet.

5 Conclusion

Write a conclusion summarizing the results of your analysis.



Worksheet C12C [side 1]Analysis of aspirin tablets

Aspirin reacts with sodium hydroxide solution. The reaction produces sodiumsalicylate. Here is a simplified form of the equation:

1 mol ofaspirin

Procedure

H0\ IC-C-H;f I

o H

+ 2NaOH

sodium salicylate

Na+-O H

\ IC-C-H

!; Io H

sodium etftanoate

Do the analysis on side 2 of this worksheet, and record your results as shown below.

ResultsRecord your results like this:

Mass of empty beaker = __ g

Mass of beaker with aspirin tablets = __ g

Titrations

Rough Accurate Accurate


Volume used/ml


CONTINUED


1 ] •~ [XJmI W .:..g I sodium hydroxide solution dilute hydrochloric acid

aspirin tablets

weighedbeaker

burette

1.00 moVL sodiumhydroxide solution

IIWeigh a 100-ml beaker.Put 5 aspirin tablets into itand weigh again.

iii Add exactly 25.0 ml of1.00 mo1jL sodiumhydroxide solution from aburette.

IIBring the contents of thebeaker to the boil. Simmergently for 15 minutes tocomplete the reaction.

distilled water

glass rod

IILet the contents of thebeaker cool. Then transferto a 250-ml graduatedflask, rinsing in any of themixture clinging to thesides of the beaker andfunnel.

funnel~(

2~m~graduatedflask IIAdd just enough distilled water to make the

total volume up to 250 ml. Stopper and mixwell.

II Transfer25.0 ml of thesolution madein step e to aconical flask,using apipette with asafety filler.

- 25 ml pipettewith

~ safety filler8 LjCOOi~lf~Sk

IIAdd 3 drops ofscreened methyl orangeindicator. Titratewith 0.100 moljLhydrochloric acid.First do a roughtitration, then twoaccurate titrations.

0.100 moVLhydrochloricacid



he 1

Calculations

1 How much sodium hydroxide was added at the start?

You measured the volume of sodium hydroxide and you know its concentration.You can therefore work out the amount of sodium hydroxide added in step a.Convert the volume from ml to L and then use this formula:

• Amount of substance = Volume x Concentration(mol) (L) (moljL)

2 How much hydrochloric acid was needed to neutralize the sodium hydroxide left afterthe reaction with the aspirin?

You work this out from the results of the titration.a Calculate the average volume of 0.100 moljL hydrochloric acid needed toneutralize the sodium hydroxide in 25 ml of the solution in step g.

b Calculate the volume of 0.100 mol/L hydrochloric acid needed to neutralize all thesodium hydroxide in the 250 ml graduated flask.

c Use the formula given in step 1of this calculation to work out the amount (mol)of hydrochloric acid needed to neutralize all the unused sodium hydroxide.

3 How much sodium hydroxide was unused after the reaction with the aspirin?

You work this out knowing the equation for the reaction of hydrochloric acid withsodium hydroxide:

NaOH(aq) + HCI(aq) - NaCI(aq) + HzO(l)1 mol 1 mol

You can see that the amount (mol) of unused sodium hydroxide is the same as theamount (mol) of hydrochloric acid needed to neutralize it.

4 How much sodium hydroxide was used up reacting with the aspirin?

The difference between your answers to steps 1and 3 of this calculation gives you theanswer to this question.

5 How much aspirin was there in the five tablets?

Now you need to look at the equation on side 1 of this worksheet.You can see that 2 mol of sodium hydroxide are needed to react with 1 mol ofaspirin.Use this information and your answer to step 4 to work out the amount (mol) ofaspirin in 5 tablets.

6 What mass of aspirin was there in the tablets?

You need this formula:

• Mass of substance = Amount of substance x Molar mass(g) (mol) (g/mol)

Use this formula and your answer to step 5 to work out the mass of aspirin in 5tablets. Then calculate the mass of aspirin in one tablet and compare your result withthe information given on the packet or bottle of tablets.



Worksheet C13AFuels

Study guideRead through the following passage. Then discuss with the other members of yourgroup the words which you think have been removed to make the twelve blanks inthe text and the diagram.

What is a good fuel?Fuels are burned to provide us with energy. Often we use this energy directly to keepus warm or to cook our food.

We also use the from burning fuels to cars, lorries, tractorsand other vehicles. In most power stations, fuels are burned in boilers designed toproduce steam at high pressure. High pressure steam is needed for the turbines whichturn the _

_____ are chemicals which react with an oxidizing agent. The overall changeswhich takes place when a fuel burns are shown in the diagram. Usually the oxidizingagent is oxygen itself. Energy is released during the reaction and new ______ are formed. Any substance which reacts with oxygen, or with anotheroxidizing agent, could be used as a fuel.

fuel

oxidizer,usually .

useful energyreleased

chemical products

What happens when a fuel burns.

The best known fuels include , diesel, coal and natural . Allthese fuels are burned in oxygen. Scientists have developed other fuels for specialpurposes. For example, a chemical called hydrazine is used as a rocket fuel. It is notburned in oxygen, but it reacts instead with concentrated nitric acid.

Not every chemical which burns is a good fuel. The fuel must plenty ofenergy when it is burned, but there are many other important points to _For most people it is probably convenience and cost which seem important. Weprefer fuels which are safe to use and which do not produce unpleasant gases andsmoke when they _



Worksheet C13BWhat makes a good fuel?

BrainstormThe purpose of a brainstorm is to produce a large number of ideas in a short time.The emphasis is on quantity not quality.

In a group, or as a class, think of as many answers as you can to the question inthe title of this worksheet. One member of the group should write all the ideas down.

RoundA round gives each person in the group a chance to express an opinion about theideas thrown up by the brainstorm.

There are two main rules:a anyone may passb no-one is allowed to criticize anyone else's contribution until the round hasfinished.

In turn complete the following statement:• 'The most important test of a good fuel for me is _

The checkl istTake the ideas from the round and fill them in the lefthand column of the tablebelow. This will be the basis for your experiment.

Write the names of some materials to test as fuels along the top.

Tests of a good fuel (ideas from ~ M tf')

Qj Qj Qj

the brainstorm and the round) u u u= = =~ ~ ~- - -rIJ rIJ rIJ.c .c .c= = =rJJ. rJJ. rJJ.

Idea 1

Idea 2

Idea 3



Worksheet C13CChoosing a good fuel

You have drawn up a checklist to help you to decide what makes a good fuel.You can fill in part of the checklist by burning the substances carefully and

watching what happens.Use ticks and crosses to rate the substances tested:

v'v' very good v' good x poor x x bad.

Fill in the rest of the checklist from your general knowledge and with the help ofreference books.

Burning tests

liquid fuels

WOOdSP~

~,

sUbstanceb~ingL..~testedo

tin lid::""":1m [JID

tripod

~

dropping pipetteliquid tobe tested mineral wool

tin lid

lEI Testing solids• Put a small quantity of thesubstance to be tested on a tin lid.• Try to light it with a burningwood splint.• If it does not catch fire, heatfrom above with a Bunsen flame.

Results

1m Testing liquids• Put a little mineral wool on a tin lid.• Moisten it with 2 to 3 drops of the liquid to be tested.• Try to light the substance with a burning wood splint.If this does not work, use a Bunsen burner.

1 Record your results in the table you prepared with Worksheet C13B.

Questions2 You can see that some substances are easier to light than others. These substanceshave a low ignition temperature. From your results, name one substance with a lowignition temperature. Name another substance with a high ignition temperature.3 Why are coal fires and solid fuel boilers often lit with gas pokers or fire lighters?4 Can you think of any disadvantages in using fuels that burn quickly?5 What are the differences between the fuels used for home heating and the fuelsused for transport?6 Which of the substances you have tested might be good for home heating? Whichwould be bad for home heating?7 Which of the substances you have tested would be likely to cause serious pollutionif used as fuels?8 Are any of the substances you have tested unsuitable for use as fuels because theyare very expensive?



Worksheet C13D [side 1]Measuring the energy released byburning fuelsIn this experiment you can compare solid, liquid and gas fuels. You will use the fuelsto heat up a measured mass of water. Then you will follow the method given insection P9.3 to calculate the quantity of energy released.

liquid fuels

III Prepare the fuel for the experiment. Weigh themass of fuel and its container.

meta fuel

tin lid

.... :""

solid

crucible gas lighter

liquid gas

stand andclamp

I II I

r

thermometer

measured volumeof water

metal can

II Ignite the fuel under the can. Stir the water.When the fuel burns out, measure the highesttemperature reached. (With the gas lighter, putout the flame when the temperature rise isabout 30°C.) When cold, reweigh thecontainer with any un burnt fuel.

Results

Add a measured volume of water to a metal can.Measure the temperature of the water. Adjustthe height of the can to suit the size of the fueland its container.

IIRepeat the experiment with the other two fuels.• Take a fresh quantity of cold water each time,and use the same volume of water.• Remember to weigh the fuel container beforeand after burning. Also remember to measure thetemperature of the water before and after burning.• You will make a fairer comparison if thetemperature rise is about the same for each fuel.• Look up the cost of each fuel in a catalogueor price list.

Name of fuel: _

Mass of container + fuel before burning = __ g

Mass of container + any fuel left after burning = __ g

Mass of fuel burned = __ g

Volume of water in the can ml

Temperature of the water at first °C

Temperature of the water after burning °C

Temperature rise of the water in the can = __ °C

_______________________________ CONTINUED



[

CalculationThe density of water is 1 g/ml.The energy transferred to the water = m x exT where

m = the mass of the water,c = the specific heating capacity of the water andT = the change in temperature.

For each of the fuels tested, calculate:• The mass of water in the can.• The energy transferred to the water in the can.• The energy released per gram of fuel burned.• The cost of 1 g of the fuel.• The energy released by the quantity of fuel which costs Ip.

Ouestions1 Suggest reasons why the experiment might not be accurate.

2 Suggest improvements to the apparatus and procedure which would make theexperiment more accurate.

3 Explain whether you think that a more accurate experiment would give a higher orlower result for the energy released per gram.

4 Comment on the advantages and disadvantages of the fuels tested.



Worksheet C13E [side 1]Air pollution - where does itcome from?In this unit you will be looking at the major gases which cause air pollution. Whatare their sources? How do the amounts produced by humans compare with theamounts of the same gases which are produced naturally?

Figure 1The air looks clean - but is it?

Photograph. R.K. Pilsbury

Figure 2 shows the sources and amounts of the major air pollutants made by humanactivities all over the world.

Pollutant gas

Carbon monoxide (CO)

Sulphur dioxide (S02)

Hydrocarbons

Nitrogen oxides (NO, N02)

Ammonia (NH 3)

Hydrogen sulphide (H2S)

Source

burning of fuels

burning of coal and oil,roasting of sulphide ores

vehicle exhausts,chemical processes

vehicle exhausts,burning of fuels

waste treatment

chemical processes,sewage treatment

Amount produced per yearthroughout the world(millions of tonnes)

300

146

88

50

4

3

Figure 2Sources of pollutant gases made by humans

________________________________ CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 301. © in this format Nuffield-Chelsea Curriculum Trust 1988.


Figure 3 shows the amounts of the same gases made by natural sources all over theworld. These natural sources have been producing the gases for millions of years.

Gas

Carbon monoxide (CO)

Sulphur dioxide (SOz)

Hydrocarbons

Nitrogen oxides (NO, NOz)

Ammonia (NH3)

Hydrogen sulphide (HzS)

Source

forest fires,biological processes

volcanoes

biological processes

bacterial action in soils,electrical storms(lightning flash)

biological decay

volcanoes andbiological decay

Amounts produced per yearthroughout the world(millions of tonnes)

3000

9

1000

160

150

65

Figure 3Sources of pollutant gases from natural sources

Ouestions and activities1 Use figure 3 to plot a bar chart showing the amount of each gas made by naturalsources each year. Use the axes on figure 4 on side 3 of this worksheet. The bar forcarbon monoxide has already been done for you.2 On top of your first bar chart, plot the amounts of each gas from human sources,using figure 2. Show clearly, by colouring or some other method, which is which. Thebar for carbon monoxide has already been done for you.3 Compare the values on the bar charts for the different gases. Which pollutant ismade much more by human activities than by natural sources?4 In what ways could the emission of this pollutant be controlled so that less isreleased into the air?

For millions of years pollutant gases from natural sources have stayed at a steadylevel in the atmosphere. This is because there are various natural ways that thepollutants get removed from the atmosphere. For example, some of the sulphurdioxide and carbon dioxide are removed from the atmosphere by dissolving in rain.

Ouestions5 Apart from rainfall, what other process removes carbon dioxide from theatmosphere?6 Even though pollutant gases are removed from the atmosphere naturally, scientistsare concerned about adding pollutants made by human activities. Why?7 Judged from the data given in figures 2 and 3, pollution by humans does notseem to be very serious compared with natural sources. Yet in many cities,particularly in Europe and North America, air pollution is an extremely seriousproblem. Why?

---------- CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SATIS Unit No. 301. © in this format Nuffield-Chelsea Curriculum Trust 1988.


]

Amount per year 3000 r---,--....,.--...-----,---,-----,--,-----,------,--,---,-------,--,-----,-----,--,--,----,--in million tonnes

2900 ~--1----+--_+-_+-__+-____1f-----+_-+_-_+_-_+-__+---i--+_-+_-_+_--+--__+-__+-

2800 ~--1---+--_+-_+-__+-____1f-----+_-+_-_+_-_+-__+---i--+_-+--_+_--+--__+-__+-

2000

1900

1800

1700

1600

1500

1400

1300

1200

1100

1000

900

800

700

600

500

400

300

200

100

o

CO natural

I

CO human

Figure 4A bar chart showing amounts of different pollutant gases produced per year

CONTINUEDCopyright © Association for Science Education 1986. Taken from ASE SAliS Unit No. 301. © in this format Nuffield-Chelsea Curriculum Trust 1988.


he ~I

Figure 5 shows how the production of sulphur dioxide by human activities in Britainhas changed since 1850.

Amount of S02 in millions oftonnes per year

8.0

6.0

4.0

2.0

1840 1860 1880 1900 1920 1940 1960 1980Year

Figure 5Changes in the production of S02 by human activities in Britain since 1850

Ouestions8 Suggest reasons why the emission of sulphur dioxide:a rose steadily between 1850 and 1900b dropped in the 1920s and 1930sc rose steeply in the 1940s, 1950s and 1960sd has been falling since the 1970s.

9 All pollutants have harmful effects. For as many of the pollutant gases as you can,find out some of their harmful effects.



Worksheet C14A [side 1]Investigating cells some metal salt solutions

Volta and the activity seriesAlessandro Yolta discovered how to make useful cells and batteries. He showed thatan electric voltage is produced when two different metals are placed in contact with aconducting solution. Yolta also showed that the size of the voltage depends on thechoice of the two metals. (See section C14.1 in your Chemistry book.)

The diagrams show three ways of setting up cells. Use one, or more, of thesearrangements to carry out investigations into the properties of cells.

solution of a salt ofmetal A

voltmeter

v

filter paper soakedin potassium nitratesolution

metal A

voltmeter

v

voltmeter

metal B

potassium nitratesolution

solution of a salt ofmetal B

filter paper soaked inpotassium nitrate solution

Investigations

1 Set up a number of cells of the same type using different pairs of metals. Measurethe voltage of each cell. Note which metal is the positive terminal and which is thenegative terminal. Can you, as Yolta did, arrange the metals in a series so that thefurther apart the metals are in the series the bigger the voltage?

2 Can you make a cell which will light a torch bulb? Or do you need a battery ofcells to do this? Can you make a 'voltaic pile' which will light a torch bulb?

3 Make each of the three types of cell shown above, but with the same pair of metalseach time. Does the design of the cell affect its voltage?

_______________________________ CONTINUED



]dilute sulphuric acid

A rechargeable cellLead-acid cells are used in car batteries. Here you can make and investigate a simplelead-acid cell.

power supply, 2-6 V d.c.

pieces oflead

dilutesulphuricacid

II Support two lead plates in abeaker containing dilute sulphuricacid. Connect them to a lowvoltage power supply. Charge thecell for a few minutes.

torch bulb or voltmeter

IIConnect the cell to a torch bulb,or to a voltmeter and note theresults. Carry out one or more ofinvestigations 4 to 6.

Investigations

4 Does the appearance of the lead change as the cell is charged and discharged?

5 Which of the variables listed below affects the voltage of the cell?

6 Which of the variables listed below affect the length of time for which the cell willlight a torch bulb?

Variables: the time spent charging the cellthe voltage used to charge the cellthe size of the pieces of leadthe distance between the pieces of leadthe concentration of the sulphuric acid.



Worksheet C15A [side 1]Particle size and the rate ofreaction of a rock with an acidA convenient example to study is the reaction of marble with dilute hydrochloricacid. The equation for the reaction is:

CaCOis) + 2HCl(aq) -- CaCI2(aq) + CO2(g) + H20(l)

In this experiment you will study the rate of reaction by measuring the change inmass which takes place because of the loss of carbon dioxide gas.

ProcedureFirst do the experiment with large marble chips. Repeat with small chips.


plug ofcotton wool

40 ml of dilutehydrochloricacid

balance

20 g ofJ:= marble chips

foldedpaper

~---~--~\ I

II•Use a measuring cylinder to put thehydrochloric acid in the flask.• Put a loose plug of cotton wool in the neckof the flask.• Weigh out 20 g of marble chips on a pieceof paper.• Place the flask and the marble on thebalance pan.• Then read the balance or press the tarebutton.

Results1 Record your readings in a table like this.

iii • As quickly as possible, add the marble tothe acid and start timing.• Replace the cotton wool plug.• Put the flask and paper back on thebalance.• Read the balance to determine the loss inmass of gas. (You will be able to read off theloss in mass directly if the balance has a tarebutton.)• Take readings at regular intervals for aboutten minutes. Then take a final reading aftertwenty minutes.

Time in minutes Loss in mass with large Loss in mass with smallmarble chips in g marble chips in g

2 Plot the results on graph paper. Show the loss in mass on the vertical (y) axis,and time on the horizontal (x) axis. Plot both sets of points on the same axes. Drawa line or curve through each set of points. Label the two lines clearly to show whichis which.

_______________________________ CONTINUED



Questions3 Why does the reading on the balance change during the experiment?

4 What is the purpose of the plug of cotton wool?

5 With both large chips and small chips the mass of marble is the same. Thevolume and concentration of the acid are also the same in both parts of theexperiment. Explain why these quantities are not changed.

6 How can you tell by looking at the graph whether the reaction is fast or slow?

7 Which reacts faster: large chips or small chips?

8 Which has the larger surface area: 20 g of large chips or 20 g of small chips?

9 How does your answer to question 8 explain your answer to question 7?

10 Why does the reaction gradually slow down and stop in both parts of theexperiment?

11 What was the final loss in mass with a large chips and b small chips?

12 Explain the connection between your answers to parts a and b of question 11.



Worksheet C15C [side 1]Temperature and the rate ofreaction of a rock with an acidA convenient example to study is the reaction of marble with dilute hydrochloricacid. The equation for the reaction is:


CaC03(s) + 2HCI(aq) - CaClz(aq) + COz(g) + HzO(l)

In this experiment you will study the rate of reaction by measuring the time taken fora fixed quantity of marble to react completely.

II• Select 4 marble chips with the same size and mass.They should be about 3 mm across.

D[~_' _r'i"_:; _~ I

marble~

chip ~thermometer

~5 ml dilutehydrochloricacid

hot water

fresh 5 mlsample ofhydrochloricacid

III • Take 5 ml of dilutehydrochloric acid in a test-tube.• Measure and record thetemperature.• Add a marble chip and starttiming.• Stop the clock when the flowof gas bubbles stops.

Results

II•Take a fresh sample ofhydrochloric acid.• Warm it up in a beakerof hot water. (See the table belowfor suitable temperatures.)• Remove the tube of acid fromthe water, and then repeatstep b.

1 Record your results in a table. Record the temperatures shown on the thermometerwhen you do the experiment. It does not matter if your values differ by a few degreesfrom those suggested below

Temperature in °C 20 30 40 50

Time taken in s

2 Plot a graph of your results. Plot the 'time taken' on the vertical (y) axis and the'temperature' on the horizontal (x) axis (with a scale running from 0 to 60 °C).

Predictions3 From your graph, predict the time which it would take for one of your marblechips to react with acid a at 25 °C and b at 45 °C. If you have time, test yourpredictions by experiment._______________________________ CONTINUED© Nuffield-Chelsea Curriculum Trust 1988.


Ouestions4 How accurately could you fix the moment when all the marble had disappeared?

5 What effect does a rise in temper~ture have on the speed of this reaction?

6 From your graph, make an estimate of the temperature rise needed to double therate of this reaction.

Rate of reaction of marble with acidIn this experiment you are measuring the time taken for a fixed mass of marble todissolve. Suppose that the mass is m g and the time is t s. Then the average rate atwhich marble reacts is

m g = (~) g/st s t

The rate is measured in grams of marble reacting per second.

In all your experiments you used the same mass of marble, so the value of m stayedthe same.

When the reaction was slow, the value of t was big, making ~ small.t

When the reaction was fast, the value of t was small, making ~ big.t

You can see that we can take ~ as a measure of the rate at which m g of marble reacts.t

7 Calculate the value of ~ for each experiment, and enter the results in a table likethis. t

Temperature in °C

Rate at which m g marble reacts with acid (~)t S

8 Plot a graph to show how the rate at which marble reacts (y axis) varies withtemperature (x axis).

9 Use this graph to make an estimate of the temperature rise needed to double therate of this reaction.



Worksheet C15D [side 1]Investigating the effect of pHon the solubility of soil mineralsIn this experiment you will mix solutions containing the ions found in soil. You willlook to see whether or not a precipitate forms, then you will go on to see if theamount of precipitate changes when the solution is made acidic or alkaline.

dilute nitric aciddilute ammonia solution

5mlofsolution 2

stir with aglass rod

5 ml ofsolution 1

i alkaliii acid

¢~7E// 7indicator paper

II •Take 5 ml of solution 1 (see the table ofresults) in a beaker and then add 5 ml ofsolution 2.• Stir and look to see whether or not aprecipitate forms at once or after standing fora little while .• Now use the mixture in the beaker forstep b.

Results

II•Test the pH of the mixture from a, thenadd dilute ammonia solution drop by dropuntil the pH is about 8.• Note whether or not the thickness of theprecipitate increases or decreases.• Next, add dilute nitric acid drop by dropuntil the pH is about 2.• Again, note any changes in the thickness ofthe precipitate.

1 Put your results in a table like this. Use this key: 0 = no precipitate,v' = slight cloudiness,

.j.j = definite precipitate,.j.j.j = very thick precipitate.

Solution 1 Solution 2 Thickness pH of the Thickness Thicknessof the mixture of the of theprecipitate precipitate precipitate(if any) (if any) (if any)on mixing at pH 8 at pH 2

sodium sulphate calcium chloride

potassium chloride ammonium nitrate

disodium iron(m) nitratehydrogensulphate

dis odium calcium chloridehydrogenphosphate

sodium sulphate manganese(n) chloride

sodium sulphate magnesium nitrate

calcium chloride ammonium sulphate

potassium chloride ammonium sulphate


NUFFIELO CO-ORDINATED SCIENCES CHEMISTRY WORKSHEETS

Ouestions2 For each of the pairs of solutions which produce precipitates when mixed:a identify the precipitate with the help of a table showing the solubilities of salts;b write word and symbol equations for the reactions.

3 Which of the salts are likely to affect the pH of the soil if used as fertilizers? (Ifnecessary, carry out further tests to check your conclusions.)

4 Which ions form insoluble precipitates at a pH 8 and b pH 2?(If necessary, carry out further tests to check your conclusions.)

5 Only soluble ions are available as nutrients for plants. What conclusions can youdraw from this experiment about the availability of soil nutrients to plants atdifferent pH values?



Worksheet e16AThe catalyst crisis I~I...:. ..

concentrated ammonia solution

The oxidation of ammonia to oxides of nitrogen is a vital stage in the manufacture offertilizers, dyestuffs and explosives. The usual catalyst for the process is platinum, butplatinum is scarce and expensive.

Imagine that you are an industrial chemist in a country suddenly cut off fromsupplies of platinum. There is an urgent need to find an alternative. You have beengiven the job of finding the best metal or alloy to use as an alternative catalyst.

A possible apparatus for the investigation is shown in the diagram. The apparatusshould be set up in a fume cupboard. An outline of the procedure is given too, butthe experiment will have to be carefully supervised by your teacher. It is veryimportant that the flow of oxygen from the cylinder is carefully controlled so that noammonia solution splashes out of the flask.

You will be supplied with a selection of wires of different metals and alloys. Youmay also be able to use wires of different lengths and thicknesses.

Plan your investigation and then ask your teacher to help you to carry out theexperiment according to your plans.

A possible procedureStep b must be carried out by your teacher.

stand andclamp

coil ofmetalwire

glass rod

----+oxygen gas

In a fume cupboard

glass tube

Watch carefully to see if there is any sign of achemical reaction.

IIWind the chosen metal wire into a coil and thenhang it from the angled piece of the glass rod.

D Turn on the oxygen supply until there is a steadystream of bubbles through the ammonia solution.

IIHeat the wire in a burner flame until it glows.Then lower the wire into position just above theammonia solution.

concentratedRepeat steps a to d using a variety of metals ammonia solutionand alloys until you find a replacement for platinum.

Results1 What changes can you observe when you see the reaction demonstrated withplatinum? Which of these observations are evidence that there is a chemical reaction?2 Which of the wires you have tested seem to act as catalysts for the reaction?3 When you use the alternative catalyst(s), does the reaction seem to go as well aswith platinum, and are your observations the same?4 How does your new catalyst compare with platinum?

Further investigations5 If you manage to find an alternative catalyst, you can try to discover how to use itto get the best results.• Does the thickness of the wire make any difference?• Does the height of the wire above the ammonia solution have any effect?• Does the way the wire is coiled matter?



Worksheet C16B [side 1]Making a fertilizer dilute sulphuric acid

ammonia solution

Ammonium phosphate is a useful fertilizer because it supplies nitrogen (N) andphosphorus (P) for plant growth and is fairly soluble. This compound can be madefrom phosphate rock in two stages. Phosphate rock consists mainly of calciumphosphate. For this experiment you will use pure calcium phosphate.

Stage 1

III Weigh out 3 g of calciumphosphate into a smallbeaker. Add 10 ml ofdistilled water.

10 ml ofdistilledwater

~

390fphosphaterock

UJ15ml of dilute stir.all the timesulphuric acid whl~e slowly .~dlngtheaCld

m Stir the mixture in thebeaker with a glass rod.Keep stirring as you slowlyadd 15 ml of dilutesulphuric acid.

IIFilter off the solid. Pour themixture down a glass rodinto the funnel to stop itrunning down the outside ofthe beaker. Keep the liquidin the beaker for stage 2.

Stage 2

labelled Petri concentrateddish r- solution from

I I step e

~_l j

IITransfer your dry productto a weighed sample tube.Reweigh to find the massof your product.

Pour into a labelled Petridish and set aside untilcrystals of ammoniumphosphate form.

n Pour off any remainingsolution and then dry thecrystals between layers ofblotting paper.

II

II Pour the solution fromstep d into an evaporatingbasin and boil off about halfof the water. (Keep a recordof the time taken toevaporate the water, sothat you can cost theprocess.)

dilute ammoniasolution (2 moVL)

IIAdd 5 ml of ammoniasolution to the solutionmade in step c. Stir.Gradually add moreammonia solution, stirringall the time, until thepH = 5. (Transfer drops ofthe solution to indicatorpaper with the glass rod totest the pH.)

_______________________________ CONTINUED© in this format Nuffield-Chelsea Curriculum Trust 1988.


]

Ouestions1 In stage 1 you have reacted calcium phosphate, Ca3(P04h with sulphuric acid tomake phosphoric acid, H3P04. This is the unfinished word equation:

calcium phosphate(s) + sulphuric acid(aq) - phosphoric acid(aq) + _What is the other product of the reaction? Complete the word equation and then tryto write a balanced symbol equation.

2 In stage 2 you have partly neutralized the phosphoric acid. The main product isdiammonium hydrogenphosphate, (NH4)2HP04'Write word and symbol equations for the reaction.What are the two other possible products?

3 Estimate the cost per kilogram of your product, using the sheet provided to guideyou. You can look up the cost of the chemicals used in a catalogue from one of thefirms which supplies chemicals to your school or college.

You can arrive at a labour cost by considering what you, or your friends, are paid forpart-time work, such as a paper round.

You can estimate your fuel costs by looking up the gas flow rate for the burner in acatalogue. You can look up the price of gas on a recent gas bill. The price of1 therm ~ the price of 2.8 cubic metres.

If the flow rate of the burner is y m 3fh, its running cost will be

(;8 x cost of 1 therm) for one hour.

The only expendable equipment is filter paper. (You can ignore capital costs, butremember that they are very important in industry.)

There is one by-product and you must decide whether it has any commercial value.You can look up the value of the pure by-product in a catalogue.

4 Calculate the, percentage by mass of nitrogen and of phosphorus in diammoniumhydrogenphosphate.

5 (Hard.) Use the two symbol equations to calculate the maximum possible yield ofdiammonium hydrogenphosphate which could be made from 3 g of calciumphosphate. How does your yield compare with this calculated value?

6 Plan an experiment to investigate the effect of the fertilizer you have made on thegrowth of plants. You can grow cress on moist filter paper. Alternatively you cangrow wheat or barley on moist cotton wool. The fertilizer concentration should besmall - about 0.05 gfL.

You might compare the fertilizer you have made with commercial products.

Worksheet C16B is based on an experiment in Chemicals for agriculture by Lyn Bossons in association with lei Agricultural Division.Experimenting with Industry series, published for the Standing Conference on School Science and Technology by the Association for Science Education.------ CONTINUED© in this format Nuffield-Chelsea Curriculum Trust 1988.


he

Laboratory costing

[si ]

Substance Operators' names

Date

A: MATERIALS Quantity Rate Cost (£)

Total cost of materials ...............................................

B: LABOUR No. of hours Rate (f/h) Cost (£)

Total cost of labour ............................................................

C:OVERHEADS Details Cost (£)

(1) Fuel

(2) Expendable equipment

(3) Other charges

Total cost of overheads ...........................................................

D: COST OF PRODUCTION

(1) Total production cost = Gross (A+B+C)

(2) Less by-products as specified (Based on catalogue value)

Total cost per batch (net) ........................................................

E: YIELD OF PROCESS PER BATCHg

=F: NET PRODUCTION COST PER KILOGRAM

D £= -- x 1000 £ ....................................................................E

Note: further comments, calculations, etc. may be made on a separate sheet and attached.

© in this format Nuffield-Chelsea Curriculum Trust 1988.


Worksheet C17 AA shortened form of the Periodic Table

Period Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Group 7 Group 8Alkali metals Alkaline earth Halogens Noble gases

metals

1 2

1H He

3 4 5 6 7 8 9 10

2u Be B C N a F Ne

11 12 13 14 15 16 17 18

3Na Mg AI Si P S CI Ar

19 20 21 31 32 33 34 35 13Sc

4 \K Ca ~ Ga Ge As Se Br Kr

Zn

37 38 39 49 50 51 52 53 54

5y

\.Rb Sr 48 In Sn Sb Te I Xe

Cd

55 56 57 81 82 83La

6 \.Cs Ba 00 TI Pb Bi

Hg

'-y---'

Transition series



Worksheet e178 [side 1]The Periodic Table

This worksheet is designed to help you to study sections C17.1 and C17.2 in yourChemistry book. You have here a copy of part of the text so that you can write on it.Most of the pictures are not included, but you can look at them in the book.

Study guideIIRead through the whole passage carefully.

IIMark the text according to the following instructions:

1 Find a sentence near the beginning of the passage which states the problemwhich D6bereiner, Newlands and Mendeleev were trying to solve. Underline thesentence and number it '1'.

2 Find two or three sentences which sum up D6bereiner's attempt at solving theproblem. Draw a box round the sentences and number it '2'.

3 Find a sentence which shows that Newlands thought he had found a bettersolution than D6bereiner. Underline the sentence and number it '3'.

4 Find two sentences which explain why Mendeleev was more successful thanother scientists in solving the problem. Underline them and label them '4a' and '4b'.

5 Underline a sentence which explains the use of the title 'Periodic Table'.Number the sentence '5'.

6 Find a paragraph which shows why Mendeleev was able to convince otherscientists that his ideas were correct. Draw a box round the paragraph andnumber it '6'.

IIPrepare a summary of the passage showing the main stages in the discovery ofthe Periodic Table. Set out your summary in the form of a flow diagram, or in aseries of short notes.

How was the Periodic Table discovered?Many new elements were discovered in the first half of the nineteenth century. At thetime a few chemists began to feel that a pattern might exist to help make sense ofthese exciting discoveries. They noticed that some of the elements had similarproperties. They knew about Dalton's work on atomic theory and began to wonder ifthere might be a connection between the chemical properties of elements and theiratomic masses.

One of the first attempts to investigate this problem was made by a Germanchemist called Johann D6bereiner (1780-1849). He studied groups of three elementswhich were similar chemically such as chlorine, bromine and iodine. He noted thatbromine seemed just half-way in its properties between chlorine and iodine. He alsonoticed that the atomic mass of bromine was the mathematical mean of the othertwo elements. He wondered if this was a coincidence and went on to look for otherexamples. He called these groups of three elements 'triads'.

D6bereiner's triads were not taken very seriously because most of the knownelements could not be fitted into the scheme. Many thought that his findings werejust coincidence. They could not see why the properties of elements should beconnected to their atomic masses.

D6bereiner's ideas were published in 1829. It was not until 1864 that the Englishchemist, John Newlands (1837-98) came up with another attempt to find a patternamong the elements. He arranged all the fifty or so known elements in order of



e ]

atomic mass. Newlands wrote: 'the eighth element starting from a given one, is a kindof repetition of the first, like the eighth note in an octave of music.' He called his rulethe 'Law of octaves'.

Look at the diagram. If you count sodium as one, and then continue countingalong the rows in the table, you get to the similar element potassium as numbereight. You can also see that one of Dobereiner's triads appears in the first part ofNewlands' table, and that the others could be found in the full table.

1 H

2 Li

3 Be

4 B

5 C

6 N

7 0

8 F

9 Na

10 Mg

11 AI

12 Si

13 P

14 S

15 CI

16 K

17 Ca

and so on

A modern version of part of Newlands' table.

Newlands' ideas were also not taken very seriously by many chemists. His law ofoctaves stopped working after the first seventeen elements. Most people felt that itwas all just chance and were put off by the idea of a link with musical scales.

It was in 1869 that a Russian chemist, Dmitri Mendeleev, published the table onwhich all later versions of the Periodic Table have been based. He succeeded whereothers had failed because he realized that Newlands had made two big mistakes. Onemistake was to assume that all the elements had already been discovered. The otherwas to think that the law of octaves would work throughout the Table with sevenelements in every row. Mendeleev realized that the later rows in the Table have to belonger than those at the beginning.

Mendeleev stated his 'periodic law' as follows: 'When the elements are arranged inorder of atomic mass, similar properties recur at intervals.'

To understand the name Periodic Table, picture a pendulum swinging backwardsand forwards. The movement of the pendulum is periodic - it traces out a repeatingpattern with time. Now look at a copy of the Periodic Table and run your eyes fromleft to right along the horizontal rows which we now call periods. The properties ofthe elements and their compounds show repeating patterns. The most obviousregular change is from metals at the left of each period to non-metals at the right andthen back to metals again.

Mendeleev made the bold move of leaving gaps in his table for undiscoveredelements. He even used his table to predict the properties of these unknownsubstances. For example, there was a gap between silicon and tin in group 4 of thetable. Mendeleev gave the name ekasilicon to the element. He predicted a number ofits properties. His predictions proved to be correct when the element was discovered.

Mendeleev was equally successful in predicting the properties of other missingelements including gallium (discovered 1875), and scandium (discovered 1879). Sowithin a few years it was impossible to doubt the usefulness of Mendeleev's tableeven though there were still problems which could not be solved.



Worksheet e18AIons into molecules at the anode

Cut out the 15 'pages' of the flick book. Arrange them in order with number 1 on top.Then staple the book together.

EB 2 EB 3

CI.l CI.l ~~ ~ CI.l.c .r:::.• .r:::. • CI.lCI.l CI.l •a. c.co a. co

U5 co U5U5• • •4 EB 5 EB 6 EBCI.l CI.l CI.lQ:i ~ ~

.r::. .r:::. .r:::.Q.J • CI.l • CI.l •a. a. c.co co co

U5 U5 U5• • •EB 8 EB 9

Q.J CI.l ~ , c:=:J~ ~ CI.l.r::. .r:::. , r=::J .r:::.

Q.J e= CI.l CI.la. c. a. c=:::Jco co co

U5 U5 r=::J U5ec:=:J10 EB 11 , EB 12 EB, r=::J c=:::J

=::::JQ.J CI.l

Q:i ~ c:::= ~.r::. .r:::. Q.J

CI.l =::::J CI.l ..ca. c. CI.lco co C.

U5 U5 coU5

13 EB 14 EB 15

CI.l ~ ~~.s::. CI.l III

CI.l.r:::. .r:::.

a. III III

(0 C. a.U5 co coU5 U5

Now make a flick book of your own to show a metal ion, such as a sodium ion,Na +, turning into a sodium atom at the cathode.


Documents

Nuffield co-ordinated sciences: chemistry worksheetsmypchem.com/root_pdf/Chemistry_Worksheets.pdf · NUFFIELD CO-ORDINATED SCIENCES CHEMISTRY WORKSHEETS Worksheet C2B [side 1] Cracking