CHEMISTRY REVIEW

Mary Rodriguez

C1. The particulate nature of matter

Demonstrate understanding of the term atom and molecule.

State the distinguishing properties of solids, liquids and gases

Describe qualitatively the

molecular structure of solids, liquids and gases.

Relate the properties of solids, liquids and gases to the forces and distances between molecules and to the motion of the molecules.

ATOM

Smallest particle of matter Neutral (#protons=#electrons)

Law of Conservation of Mass

Mass cannot be created or destroyed, it can only be transformed into energy

In a Chemical Reaction the mass of the products equals the mass of the reactants

http://sciencepark.etacude.com/chemistry/law.php

Molecule

The smallest physical unit of an element or compound. Consisting of one or more like atoms in an element and two or more different atoms in a compound.

Diatomic Molecules

Nitrogen Oxygen Hydrogen Fluorine Chlorine Bromine Iodine

Experimental techniques 2.1 Methods of separation and

purification Describe paper chromatography. Interpret simple chromatograms. Describe methods of separation and

purification: filtration, crystallisation, distillation, fractional distillation.

Understand the importance of purity in substances in everyday life, e.g. foodstuffs and drugs.

Identify substances and assess their purity from melting point and boiling point information.

Suggest suitable purification techniques, given information about the substances involved.

What is Chromatography?Chromatography is a technique for separating mixtures into their components in order to analyze, identify, purify, and/or quantify the mixture or components.

Separate

• Analyze

• Identify

• Purify

• QuantifyComponentsMixture

Uses for Chromatography

Chromatography is used by scientists to:

• Analyze – examine a mixture, its components, and their relations to one another

• Identify – determine the identity of a mixture or components based on known components

• Purify – separate components in order to isolate one of interest for further study

• Quantify – determine the amount of the a mixture and/or the components present in the sample

Uses for ChromatographyReal-life examples of uses for

chromatography:

• Pharmaceutical Company – determine amount of each chemical found in new product

• Hospital – detect blood or alcohol levels in a patient’s blood stream

• Law Enforcement – to compare a sample found at a crime scene to samples from suspects

• Environmental Agency – determine the level of pollutants in the water supply

• Manufacturing Plant – to purify a chemical needed to make a product

Definition of Chromatography Detailed Definition:

Chromatography is a laboratory technique that separates components within a mixture by using the differential affinities of the components for a mobile medium and for a stationary adsorbing medium through which they pass.

Terminology:

• Differential – showing a difference, distinctive• Affinity – natural attraction or force between things• Mobile Medium – gas or liquid that carries the

components (mobile phase)• Stationary Medium – the part of the apparatus that

does not move with the sample (stationary phase)

Simplified Definition:

Chromatography separates the components of a mixture by their distinctive attraction to the mobile phase and the stationary phase.

Explanation:

• Compound is placed on stationary phase• Mobile phase passes through the stationary

phase• Mobile phase solubilizes the components• Mobile phase carries the individual

components a certain distance through the stationary phase, depending on their attraction to both of the phases

Definition of Chromatography

Illustration of Chromatography

Components

Affinity to Stationary Phase

Affinity to Mobile Phase

Blue ---------------- Insoluble in Mobile Phase

Black

Red

Yellow

Mixture Components

Separation

Stationary Phase

Mobile Phase

• Liquid Chromatography – separates liquid samples with a liquid solvent (mobile phase) and a column composed of solid beads (stationary phase)

• Gas Chromatography – separates vaporized samples with a carrier gas (mobile phase) and a column composed of a liquid or of solid beads (stationary phase)

• Paper Chromatography – separates dried liquid samples with a liquid solvent (mobile phase) and a paper strip (stationary phase)

• Thin-Layer Chromatography – separates dried liquid samples with a liquid solvent (mobile phase) and a glass plate covered with a thin layer of alumina or silica gel (stationary phase)

Types of Chromatography

(A) uses charge, (B) uses pores, and (C) uses covalent bonds to create the differential affinities among the mixture components for the stationary phase.

Principles of Paper Chromatography

Capillary Action – the movement of liquid within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension. The liquid is able to move up the filter paper because its attraction to itself is stronger than the force of gravity.

Solubility – the degree to which a material (solute) dissolves into a solvent. Solutes dissolve into solvents that have similar properties. (Like dissolves like) This allows different solutes to be separated by different combinations of solvents.

Separation of components depends on both their solubility in the mobile phase and their differential affinity to the mobile phase and the stationary phase.

Paper Chromatography Experiment

What Color is that Sharpie?

Overview of the Experiment

Purpose: To introduce students to the principles and terminology of chromatography and demonstrate separation of the dyes in Sharpie Pens with paper chromatography.

Time Required: Prep. time: 10 minutesExperiment time: 45 minutes

Costs: Less than $10

Materials List

6 beakers or jars 6 covers or lids Distilled H2O Isopropanol Graduated cylinder 6 strips of filter paper Different colors of

Sharpie pens Pencil Ruler Scissors Tape

Preparing the Isopropanol Solutions

• Prepare 15 ml of the following isopropanol solutions in appropriately labeled beakers:

- 0%, 5%, 10%, 20%, 50%, and 100%

Preparing the Chromatography Strips

Cut 6 strips of filter paper

Draw a line 1 cm above the bottom edge of the strip with the pencil

Label each strip with its corresponding solution

Place a spot from each pen on your starting line

Developing the Chromatograms

Place the strips in the beakers

Make sure the solution does not come above your start line

Keep the beakers covered

Let strips develop until the ascending solution front is about 2 cm from the top of the strip

Remove the strips and let them dry

Developing the Chromatograms

Developing the Chromatograms

Observing the Chromatograms

Concentration of Isopropanol

0% 20% 50% 70% 100%

Black Dye

1. Dyes separated – purple and black

2. Not soluble in low concentrations of isopropanol

3. Partially soluble in concentrations of isopropanol >20%

Concentration of Isopropanol

0% 20% 50% 70% 100%

Blue Dye

Concentration of Isopropanol

0% 20% 50% 70% 100%

1. Dye separated – blue2. Not very soluble in low

concentrations of isopropanol

3. Completely soluble in high concentrations of isopropanol

Green Dye

Concentration of Isopropanol

0% 20% 50% 70% 100%

1. Dye separated – blue and yellow

2. Blue – Soluble in concentrations of isopropanol >20%

3. Yellow – Soluble in concentrations of isopropanol >0%

Red Dye1. Dyes separated – red and yellow2. Yellow –soluble in low concentrations of isopropanol and

less soluble in high concentrations of isopropanol

Concentration of Isopropanol

0% 20% 50% 70% 100%

3. Red – slightly soluble in low concentrations of isopropanol, and more soluble in concentrations of isopropanol >20%

FILTRATION

Is a method of separation used to remove undissolved solids from liquids.

Here, filter paper and a glass funnel is used to separate the solid from the liquid.

The filter works by allowing the liquid to flow through the paper, but not the solid.

This is because the particles of the solid are too big to pass through the minute holes in the filter paper.

At the end of the filtration, you are left the residue of the solid on the filter paper and the liquid in another container.

CRYSTALLIZATION

Is used to separate dissolved solids from liquids, unlike filtration.

The solution is heated in an open container. This allows the solvent to evaporate, leaving us

with a saturated solution. The saturated solution is a solvent which contains

as much of the solid dissolved within it. The saturated solution is left to cool. At this point, crystals of the solid will grow in the

solution. When the solution has completely evaporated, you

are left with the crystallized solids. Distillation:

DISTILLATION

Is a method of separation used to extract a pure liquid from a mixture.

How it works: Credit: http://

commons.wikimedia.org/w/index.php?title=User:Ayapici&action=edit&redlink=1

In this example, we will use a mixture of both ethanol and water.

The mixture is first heated in a round bottomed flask.

The fact that ethanol has lower boiling point is crucial.

At 78oc, the ethanol will evaporate into vapour. At this point, the vapour will travel down the

condenser filled with cool, running water and be cooled down into a liquid.

The ethanol liquid (distillate) will be collected into a beaker whilst the water is left in the flask.

The ethanol is now separated from the water.

FRACTIONAL DISTILLATION

Is similar to the normal distillation method above. Separates a liquid mixture into its individual components How it works: http://en.wikipedia.org/wiki/File:Crude_Oil_Distillation.png The above diagram uses the example of crude oil. Like distillation, the mixture is heated and evaporated. The substances within the crude oil have different boiling

points and they each evaporate at different temperatures. The temperature decreases as the gases go up the fractioning

column. The smaller molecules condense at the higher portions of the

column at lower temperatures. Conversely, the  larger molecules sink to the bottom and

condense at higher temperatures

FRACTIONAL DISTILLATION OF AIR

The Importance of Purity in substances

Purifying and separation methods allow us to obtain specific substances and chemicals needed for our everyday life. Like above, the separation of crude oil into its components is essential, as the petrol allows us to keep our cars running and the naphtha is used for making plastics.

Purifying chemicals and substances is important, especially if we ingest it. Impurities in things like drugs and food could be potentially hazardous and detrimental to our health if swallowed.

3.1 Physical and chemical changes

Identify physical and chemical changes, and understand the differences between them.

Chemical & Physical Changes

Note: the physical and chemical properties of the atoms will change when they combine to another atom

3.2 Elements, compounds and mixtures

1 Describe the differences between elements, compounds and mixtures.

Demonstrate understanding of the concepts of element, compound and mixture.

MATTER

SUBSTANCEComposition is definite (FIXED COMPOSITION)

MIXTUREComposition is variable; Two or more elements or compounds mixed together via physical means

ELEMENTOne Kind of atom (ALL ATOMS MATCH)

COMPOUNDTwo or more elements combined via chemical reaction

HOMOGENOUSEvenly mixed

HETEROGENOUS Unevenly mixed

3.3 Atomic structure and the Periodic Table

1 Describe the structure of an atom in terms of electrons and a nucleus containing protons and neutrons.

3 State the relative charges and approximate relative masses of protons, neutrons and electrons.

4 Define proton number and nucleon number. 5 Use proton number and the simple structure of atoms to

explain the basis of the Periodic Table (see C9), with special reference to the elements of proton number 1 to 20.

6 Define isotopes. 2 Describe the build-up of electrons in ‘shells’ and

understand the significance of the noble gas electronic structures and of valency electrons (the ideas of the distribution of electrons in s and p orbitals and in d block elements are not required).

Proton=1 amuNeutron=1 amuElectron= 0 amu

Proton Number:Atomic NumberWhole Number

Nucleon Number:Atomic Mass(Protons+Neutrons)

Isotopes Isotopes

The number of protons and electrons is the same The number of neutrons changes for that atom or

element

Valence Electrons The electrons on the

outer most shell of the atom.

S(2) P(6) D(10) F(14)

Octet Rule- each atom wants to have at a full shell of 8 valence electrons.

3.4 Ions and ionic bonds 1 Describe the formation of ions by electron

loss or gain. 2 Describe the formation of ionic bonds

between metals and non-metals as exemplified by elements from Groups I and VII.

3 Explain the formation of ionic bonds between metallic and non-metallic elements.

4 Describe the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions, exemplified by the sodium chloride structure.

OCTATE RULE

Atoms want a full outer shell, with 8 valence electrons and will lose or steal electrons from other atoms to fulfill this.

Ions

The number of protons and neutrons stays the same

The number of electrons changes for that atom or element

http://misterguch.brinkster.net/ionic.html

Cations: Metals lose their electrons to fulfill the octate rule(and become positive)

Anions: Non-Metals steal electrons from the Metals to fill up their orbitals (and become negative)

3.5 Molecules and covalent bonds

1 State that non-metallic elements form nonionic compounds using a different type of bonding called covalent bonding.

3 Describe the differences in volatility solubility and electrical conductivity between ionic and covalent compounds.

2 Draw dot-and-cross diagrams to represent the sharing of electron pairs to form single covalent bonds in simple molecules, exemplified by (but not restricted to) H2, Cl2, H2O, CH4 and HCl.

4 Draw dot-and-cross diagrams to represent the multiple bonding in N2, C2H4 and CO2.

COVALENT BONDING

The bonding between non-metals The electrons are shared with single,

double, and triple bonds

3.6 Giant structures

1 Describe the giant covalent structures of graphite and diamond.

2 Relate their structures to the use of graphite as a lubricant and of diamond in cutting.

3 Describe the structure of silicon(IV) oxide (silicon dioxide).

C4. Stoichiometry 1 Use the symbols of the elements to write the formulae of simple

compounds. 2 Deduce the formula of a simple compound from the relative

numbers of atoms present. 3 Deduce the formula of a simple compound from a model or a

diagrammatic representation. 4 Construct and use word equations. 5 Determine the formula of an ionic compound from the charges on

the ions present. 6 Construct and use symbolic equations with state symbols,

including ionic equations. 7 Deduce the balanced equation for a chemical reaction, given

relevant information. 8 Define relative atomic mass, Ar. 9 Define relative molecular mass, Mr, as the sum of the relative

atomic masses (relative formula mass or Mr will be used for ionic compounds).

Symbols Symbol Meaning

+ Separates two or more reactants or products

→ Separates reactants from products

(s) Identifies solid state

(l) Identifies liquid state

(g) Identifies gaseous state

(aq) Identifies water solution(aqueous)-mixture of water

Chemical Reactions & Balancing

Reactants → Product(s) C+O2 → CO2

CO2 + 2 H2→CH4+O2

In the law of conservation of mass it is stated that we can neither lose or gain mass so during a chemical equation what

we put in (reactants) has to equal what is put out (product) For example: If you start

with 2 hydrogen atoms and 1 oxygen atom as your reactants then there has to be 2 hydrogen atoms and 1 oxygen atom

http://misterguch.brinkster.net/eqnbalance.html

Reactions Decomposition -when one

breaks down, or decomposes, into two or more substances AB→A+B 2H2O(l)→2H2(g)+O2(g)

Single Displacement-when one element replaces another element in a compound A+BC→AC+B

Double Displacement-when the positive ion of

one compound replaces the positive ion of the other to form two new compounds AB+CD→AD+CB Ppt. (s) Produce H2O Get Gas as a product

Reversible H2O↔OH+ +H+

Re-dox-you can reduce oxidation number(gain electron) or oxidized (lose electron)

Chemical Reaction Rates Factors that change the rates are

Concentration When the concentration is increased of the reactants then

the rate increases too Surface area

More surface are the faster the reaction is Temperature

Endo-Cold Exo-Hot

Catalysts-A substance that increases the rate of the reaction and doesn’t change

4.1 The mole concept 1 Define the mole in terms of a specific

number of particles called Avogadro’s constant. (Questions requiring recall of Avogadro’s constant will not be set.).

2 Use the molar gas volume, taken as 24 dm3 at room temperature and pressure.

3 Calculate stoichiometric reacting masses and reacting volumes of solutions; solution concentrations will be expressed in mol / dm3. (Calculations involving the idea of limiting reactants may be set.)

C5. Electricity and chemistry

1 State that electrolysis is the chemical effect of electricity on ionic compounds, causing them to break up into simpler substances, usually elements.

2 Use the terms electrode, electrolyte, anode and cathode. 3 Describe electrolysis in terms of the ions present and the reactions

at the electrodes. 4 Describe the electrode products, using inert electrodes, in the

electrolysis of: • molten lead(II) bromide, • aqueous copper chloride, • dilute sulfuric acid.

5 State and use the general principle that metals or hydrogen are formed at the negative electrode (cathode), and that nonmetals (other than hydrogen) are formed at the positive electrode (anode).

6 Relate the products of electrolysis to the electrolyte and electrodes used, exemplified by the specific examples in the Core together with aqueous copper(II) sulfate using carbon electrodes and using copper electrodes (as used in the refining of copper).

C5. Electricity and chemistry (Continued)

7 Describe the electroplating of metals, using laboratory apparatus.

8 Predict the products of the electrolysis of a specified binary compound in the molten state, or in aqueous solution.

9 Describe, in outline, the chemistry of the manufacture of aluminium from pure aluminium oxide in

molten cryolite, chlorine, hydrogen and sodium hydroxide from

concentrated aqueous sodium chloride.

Reactivity Series http://en.wikipedia.org/wiki/Reactivity_series

On the reactivity series, hydrogen is less reactive than sodium. Hence hydrogen will be produced at the cathode (negative electrode.)

A metal will be produced if it is less reactive than hydrogen

Hydrogen will be produced if the metal is more reactive

The less reactive cation will be produced at the cathode.

Reduction occurs at the cathode. Cations are reduced (become neutral) by the e- at the cathode.

Hydrogen formed

When the hydrogen reaches the cathode, it is reduced (gains electrons.) The e- flowing in the circuit are attracted to the cation and the hydrogen ions are neutralized (reduced to neutral.2H+ + e - → H2

Electroylsis video

http://www.mybigcampus.com/items/hygrogen-and-oxygen-from-water?vc0d22fa0-afd1-012e-fa88-129babfcd502

http://www.mybigcampus.com/items/make-copper-sulfate-from-copper-and-sulfuric-acid-3-ways---296671?v0c8fa3e0-9bb6-012e-4534-569eeb3c0b2d

Copper purification

Impure copper would be used as the anode and pure copper would be used as the cathode in a copper sulfate solution.

Electricity is applied and the copper atoms in the anode are oxidized(their e- removed.)Cu – 2e- → Cu2+

The copper ions dissolve into the copper sulfate solution and are attracted to the copper cathode where they are reduced (e- added) and pure copper is added to the cathode.Cu2+ + 2e- → Cu

As the rxn continues the cathode grows larger and the anode shrinks.

Electroplating

Metal plating is similar to metal purification. The object to be plated becomes the cathode. The metal you are plating (coating) on the

object is the anode. The electrolyte used in electroplating must

contain the same ions as the metal you are plating onto the object.

When electricity flows the metal that is being plated onto the object is first oxidized and become ions in the solution. They are attacted to the cathode and reduced. Leaving a layer of metal on the object.

Salt mystery

The electrolysis of aqueous solutions of sodium chloride doesn't give the same products as electrolysis of molten sodium chloride.

Electrolysis of molten NaCl decomposes this compound into its elements.

2 NaCl(l)→2 Na(l) + Cl2(g)

Salt mystery part 2

Electrolysis of aqueous NaCl solutions gives a mixture of hydrogen and chlorine gas and an aqueous sodium hydroxide solution

2 NaCl(aq ) + 2 H2O(l) →2 Na+(aq) + 2 OH-

(aq) + H2(g)

+ Cl2(g)

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch20/faraday.php#aq

Aluminum smelting

The Hall–Héroult process is the major industrial process for the production of aluminium. It involves dissolving alumina in molten cryolite, and electrolysing the molten salt bath to obtain pure aluminium metal.

The Process

The molten mixture of cryolite, alumina, aluminum fluoride is electrolyzed using DC. Aluminum is deposited at the cathode (precipitate), and oxygen with carbon from the anode produces CO2. The rate of reaction proportional

to the amount of current. While solid cryolite is denser than solid aluminum (at room temperature), liquid

aluminum is denser than the molten cryolite and Al sinks to the bottom of the electrolytic cell, where it is periodically collected.

http://www.gcsescience.com/ex11.htm

Electrolysis and Redox compared

A , chemical reactions where electrons are transferred between molecules are called oxidation/reduction (redox) reactions.

In contrast, chemical reactions driven by an external applied voltage = electrolysis. In general, electrolysis deals with situations where oxidation and reduction reactions are separated in space or time, and connected by an external electric circuit.

REDOX

The loss of electrons from an atom or molecule is called oxidation.

The gain of electrons is reduction. mnemonic devices. "OIL RIG" (Oxidation Is Loss, Reduction Is

Gain) "LEO" the lion says "GER" (Lose Electrons:

Oxidization, Gain Electrons: Reduction).