chemistry igcse sow

Chemistry for IGCSE, 1

Chemistry for IGCSE, 1.1 Solids, liquids and gases, pp. 23 (S refers to material in the supplement) Approximate timing for this section: 80 minutes (including experiments)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the states of matter and explain their interconversion in terms of the kinetic particle theory (1 core)

Learning Objectives

The properties of solids, liquids and

gases can be explained in terms of

the closeness of the particles and the

extent of movement of the particles The terms melting point and boiling

point are used for specific changes of

state

The meaning of the terms melting,

boiling, freezing, condensing

Energy is absorbed on melting and

boiling

Energy is released on condensing

and freezingSuggested Teaching Activities

This section may be mainly for revision, but many students still get confused with the structure of liquids so it is best to concentrate on this and on the energy aspects of change of state.

The bulk properties of solids liquids and gases can be demonstrated using a beaker and a block of ice, then melting the ice and boiling the water.The difference between a gas and a vapour could be mentioned.

Tables of data about melting points and boiling points could be used and students draw thermometers to show at what temperatures the substance is solid, liquid or gas. Students may then be asked to identify the state of a substance at a certain temperature. Focus on substances which are gases or liquids at room temperature.

The terms melting, evaporating (and boiling), condensing and freezing could then be introduced, together with a discussion of the energy changes involved.

The arrangement and motion of particles in solids, liquids and gases can then be suggested. This can be done as a kinaesthetic activity by the students.Extension and Consolidation

The fact that some substances have melting and boiling points that are negative often causes difficulties, and additional questions might be given about the state of these substances at certain temperatures below 0oC.

Students could make a flickbook to show the movement of the particles of liquids and gases, or to show the change in arrangement and motion of the particles when a solid changes to a liquid and a liquid to a vapour. This is suitable for homework or for less able students.More advanced students could consider the energy changes on change of state in terms of forces between the particles.

Learning Outcomes

Describe the difference in

arrangements and motion of particles

in the three states of matter

Explain change of state in terms of

particles when substances are heated

or cooled Practical Work and Resources

A cooling or heating curve for salicylic acid could be undertaken by students to emphasise that heat is absorbed when a solid melts and is released when a liquid solidifies the horizontal portion of the curve indicating the point where energy is absorbed or being released see Chemistry for IGCSE, p.3. This can also be demonstrated using a temperature probe attached to a data logger and computer.

A kinetic particle model could also be used (ball bearings in a vertical tube with vibrator at one end to give the ball bearings more and more energy to model the change from solid to liquid to vapour).

Show a computer animation to show the arrangement and motion of the particles in solids, liquids and gases.

Chemistry for IGCSE, 1.2 Diffusion, pp. 45 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (including experiments)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe and explain diffusion (1 core)

Describe evidence for the movement of particles in gases and liquids (1 core)

Describe dependence of rate of diffusion on molecular mass treated qualitatively (1 supplement)

Learning Objectives

The kinetic particle theory states that

molecules in liquids and gases are

constantly moving and in solids they

are constantly vibrating

Diffusion is the random movement

of particles which leads to them

spreading out

Evidence for the movement of

particles comes from experiments

showing the bulk flow of substances,

e.g. bromine vapour spreading out/

perfumes being smelled / ink

diffusing into water

Substances with a higher relative

molecular mass diffuse slower than

those with a lower relative molecular

mass (S)

Suggested Teaching Activities

Diffusion is best discussed in terms of randomly moving particles. There is no attempt at this stage to define what the particles are.

Some planning is needed to set up the experiments in advance.

You could start by placing an ester or other scented substance at the front of the class and asking students to put their hands up when they smell the scent.Demonstrate one or more of the other diffusion experiments, preferably one involving gases and one involving diffusion in solution.

Get students to suggest what is happening in terms of movement of particles stress that the movement is random.

Make sure that students distinguish between processes of evaporation and diffusion (or dissolving and diffusion for a coloured solid placed in liquid).

Complete the session by getting the students to suggest that diffusion is one piece of evidence for the movement of particles (kinetic particle theory).

Finally the idea of relating the rate of diffusion to relative molecular mass of the molecules can be discussed. You can just talk about the mass of the molecules at present, since the idea of relative molecular mass has not been covered yet. Refer to the experiment involving a long tube with ammonia and hydrogen chloride gas diffusing. The white ring appears nearer the hydrogen chloride end of the tube because hydrogen chloride molecules are heavier than those of ammonia and move slower.Extension and Consolidation

Students could make a flickbook showing a gas diffusing into air (show air particles as well as e.g. bromine particles).Give further examples of diffusion involving mixing of different liquids. More advanced students could be asked why if lead and gold are held together for a long time, they appear to become joined in one block a rather rare example of diffusion in solids.

More advanced students can predict the effect of similar experiments to the white ring experiment, for example using different gases which diffuse and then react, e.g. methylamine and hydrogen chloride.

Learning Outcomes

Describe and explain diffusion Explain how the rate of diffusion

depends on the mass of the molecules

(S)Practical Work and Resources

Set up a syringe with ink in the bottom and water at the top and watch the ink diffuse into the water over a few days.Observe the dissolving then diffusion of a crystal of potassium manganate(vii) placed in the bottom of a beaker of water.

Demonstrate the diffusion of bromine in air (see Chemistry for IGCSE, p.5).

Demonstrate rate of diffusion using a long glass tube with hydrochloric acid at one end and ammonia at the other (see Chemistry for IGCSE, p.5)

Chemistry for IGCSE, 1.3, Apparatus for measuring, pp. 67 (S refers to material in the supplement)Approximate timing for this section: 40 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Name appropriate apparatus for measurement of time, temperature, mass and volume including burettes, pipettes and measuring cylinders (2.1 core)

Learning Objectives

Mass is measured in grams,

temperature in oC, and volume in cm3

or dm3 The measuring apparatus selected for

an experiment depends on the

accuracy required in the experiment

Know the uses of standard laboratory

glassware, including the burette, gas

syringe and condenserSuggested Teaching Activities

Introduce students to pieces of laboratory glassware. Much of this section could be introduced or returned to at appropriate points in the course rather than doing this as a section.

It is especially important that students distinguish between volumetric pipettes and just ordinary pipettes. Students should be able to understand the conventions of drawing sectional diagrams of the apparatus as well as identifying apparatus in the round.

This can be done through a few simple experiments on measuring volumes of gasses and liquids (see Practical work below). It must be stressed, though, that at this stage, the emphasis is on using the correct apparatus for the correct job rather than focusing on the particular chemical reactions. The selection of apparatus according to the degree of accuracy required is also important.

Methods of collecting gases could be done here or later when the tests for different gases are discussed.Students could be given a series of cards with pictures of apparatus and asked to match them up with the job they are used for. Extension and Consolidation

Students could label apparatus set up in a variety of ways, e.g. for distillation, a flask with a reflux condenser, titration apparatus.If insufficient apparatus is available, a demonstration set should be used or diagrams.

Students could be asked to criticise various sectional diagrams of apparatus, e.g. with mistakes such as corks cutting across the tubes, absence of a proper closed system, etc.

Learning Outcomes

Explain how to measure mass, time

and temperature

Explain how to measure volume

Practical Work and Resources

Reading a burette and using it to deliver a fixed amount of liquid into a flask (which could have an indicator in it).Using a volumetric pipette / volumetric flask.Collecting a gas, e.g. carbon dioxide from acid + carbonate in an upturned measuring cylinder over water and using a stopclock to measure the volume of gas produced in 10 seconds.

Chemistry for IGCSE, 11.4, Whats that gas? pp.13839 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (but 30 minutes if tests demonstrated)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the following tests to identify gases: ammonia (using damp red litmus paper), carbon dioxide (using limewater), chlorine (using damp litmus paper) , hydrogen

(using a lighted splint), oxygen (using a glowing splint) (8.4 core)

Learning Objectives

Oxygen relights a glowing splint

Hydrogen gives a squeaky pop with a

lighted splint

Chlorine bleaches damp litmus paper

Carbon dioxide turns limewater

milky

Ammonia turns damp red litmus

paper blueSuggested Teaching Activities

This section is introduced early in the course to ensure that students are conversant with the common gases that they will meet throughout the course and to gain more experience with apparatus following on from the last section.

Introduce the section by asking students how they would collect gases that are heavier than air or are lighter than air. The different methods of collection can then be demonstrated using some standard reactions (see practical work).

Relate the insolubility of some gases to the fact that they can be collected over water.

The fact that some gases are denser than air and others are lighter than air can be demonstrated by simple test tube experiments in the following way (use the fume cupboard): take a test tube of ammonia, put a moist red litmus paper a few centimetres above the tube, then time how long it takes for the litmus to turn a definite blue colour. Repeat with the tube inverted and the litmus the same distance away from the mouth of the tube.

The tests are best done with previously prepared test tubes of gas, or gas from a cylinder or Kipps apparatus, so that students concentrate on the gas rather than on the chemical reaction producing the gas. Extension and Consolidation

Students could be given various problems of a practical nature to solve involving method of gas collection e.g. of gases they are unfamiliar with e.g. sulfur dioxide.

Students could be given a set of cards about gas tests and asked to match the gas with the correct test and with the correct result.

Learning Outcomes

Describe the tests for hydrogen and

oxygen

Describe how litmus is used to test

for ammonia and chlorine

Describe that carbon dioxide turns

limewater milky


Students test for carbon dioxide using limewater (acid on carbonate) (see Chemistry for IGCSE, p.139)Students test for hydrogen (a calcium chip in acid) (see Chemistry for IGCSE, p.138)

Students test for oxygen (potassium manganate(vii) heated) (see Chemistry for IGCSE, p.138)

Demonstration test for chlorine (sodium chlorate(i) and hydrochloric acid) (See Chemistry for IGCSE, p.139)

Chemistry for IGCSE, 1.4 Paper chromatography, pp. 89 and p. 243 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (including experiments)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe paper chromatography (2.2a core) Interpret simple chromatograms (2.2a core)

Interpret simple chromatograms including the use of Rf values (2.2a supplement)

Outline how chromatography techniques can be applied to colourless substances by exposing chromatograms to substances called locating agents (2.2a supplement)

Learning Objectives

Chromatography is used to separate

and purify mixtures of coloured

compounds using a filter paper and

solvent

Chromatography can be used to

identify compounds

Locating agents are used to make

colourless compounds visible on

chromatograms (S) Compounds on a chromatogram can

be identified by their typical Rf

values (S)Suggested Teaching Activities

Start by showing a variety of coloured substances which are mixtures of coloured pigments (dyes), e.g. colourings in sweets, inks in felt-tip pens.Place a spot of ink on a piece of moist filter paper and after a few seconds note the coloured bands (black ink or blue ink are best for this).

Introduce the idea of chromatography to separate different colours.Students can then carry out chromatography using coloured sweets or non-permanent felt-tip pen colourings. Stress the importance of the solvent being below the origin (base) line and the fact that the base line should be in pencil not ink!Students could compare the heights of spots and calculate Rf values.

They might also identify compounds (amino acids) from known Rf values if a mixture of these is available; or they could do this from diagrams.

The importance of chromatography for identifying the absence of amino acids in some diseases could be mentioned. Extension and Consolidation

Students could be asked to draw / complete diagrams of chromatography apparatus. Students could carry out Rf analysis and identification of compounds for homework

Extend to demonstrate the chromatography of amino acid using ninhydrin as a locating agent (fume cupboard) then warming the chromatogram (after the solvent has evaporated) in an oven to bring out the purple colour.Students could also research food colourings and some problems associated with their use e.g. Sudan dyes / tartrazine.

Learning Outcomes

Describe paper chromatography

Interpret simple chromatograms

Interpret chromatograms using Rf values (S) Outline how chromatography

techniques can be applied to

colourless substances using locating

agents (S)Practical Work and Resources

Carry out chromatography of sweet colourings or inks (use a small spot of ink felt-tip pens are useful for this) (see Chemistry for IGCSE, p.9).Demonstration chromatography of chlorophyll (extract chlorophyll with warm or petroleum ether or ethanol flammable and carry out chromatography with propanone or another suitable solvent) links with photosynthesis.Video clips of chromatography of various types are readily available and can be shown.

Chemistry for IGCSE, 1.5 Is that chemical pure? pp.1011 (S refers to material in the supplement)Approximate timing for this section: 40 minutes including practicals (otherwise 10 minutes)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Identify substances and assess their purity from melting point and boiling point information (2.2a core)

Understand the importance of purity in substances in everyday life, e.g. foodstuffs and drugs (2.2a core)

Learning Objectives

Medical drugs and food additives

must contain pure compounds to

avoid harming people

A pure substance melts and boils at a

sharp (definite) temperature. An

impure substance melts or boils over

a range of temperatures

Impurities lower the freezing point

and raise the boiling point of a

substance Suggested Teaching Activities

Start by asking students about the range of substances we either take into our bodies or put on our skins. This leads to a discussion of purity. Use labels from bottles of mineral water to indicate that mineral water is not pure water. You could also discuss the concept of pure orange juice.

The importance of purity can then be introduced in terms of the compounds that go into medicines and foodstuffs. Impurities are present in these, but they should be uncontaminated by harmful impurities.

Develop the idea of how to test whether a substance is pure or not by measuring melting and boiling points (see practicals) leading to the idea that pure solids have sharp melting points and impure ones melt over a range of temperatures. Extension and Consolidation

Students could undertake a literature/ internet search to find examples of where impurities have got into foods (bacteria / poisons e.g. mercury in fish) or into drinking water e.g. aluminium compounds / insecticides / heavy metal ions.

Learning Outcomes

Assess purity from information about

melting and boiling points

Understand the importance of purity

of substances used in everyday life


Students measure the boiling point of distilled water and salt water.

Students measure the melting point of crushed ice in a filter funnel with and without added salt.

Chemistry for IGCSE, 1.6 Methods of purification, pp. 1213 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (including experiments)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe methods of purification by the use of a suitable solvent, filtration, crystallisation (2.2b core)

Learning Objectives

Solids can be separated from

solutions by filtering (or decanting or

centrifuging)

Crystals are formed when a solution

is partly evaporated to saturation

points then allowed to cool

Solvent extraction is used to separate

substances, one of which is more

soluble in the solvent than the otherSuggested Teaching Activities

Demonstrate addition of aqueous sodium hydroxide to aqueous copper (ii) sulfate and filter off the precipitate. While doing this, introduce or reintroduce the terms solvent, solution, precipitate, filtrate and residue. You could discuss why filtration is often used rather than decanting or centrifuging.

Show samples or pictures of crystals showing their regular structure.

Introduce the standard method of crystallisation, stressing that to form good crystals the solution should be heated only to the crystallisation point.

Students could make their own crystals of, e.g., copper(ii) sulfate.

Demonstrate solvent extraction, stressing the fact that many substances are soluble in water but insoluble in organic solvents or vice versa (see below). Extension and Consolidation

Make different types of crystal. Investigate different crystal shapes and the range of substances which form crystals. This might form a suitable internet search, perhaps for homework.Give a number of separation problems when given suitable information about solubilities of the individual substances concerned.

Learning Outcomes

Describe the processes of filtration

and crystallisation

Describe how to use a solvent to

extract a particular chemical


Students could make crystals of copper sulfate from a dilute solution of copper sulfate (or mixture of copper sulfate solution and sand) (see Chemistry for IGCSE, p.13).Students separate sand from salt (sodium chloride) by dissolving the salt in water, filtering, then crystallising the salt.Demonstrate the solvent extraction of chlorophyll: grind plant material in a small amount of water and put the mixture into a separating funnel, then add petroleum ether and shake chlorophyll is extracted into the solvent layer.Demonstrate the extraction of iodine from aqueous solution into hexane (see Chemistry for IGCSE, p.13).

Chemistry for IGCSE, 1.7 More about purification, pp. 1415 (S refers to material in the supplement)Approximate timing for this section: 40 minutes (including practical demonstrations)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe methods of purification by the use of distillation including the use of the fractionating column (2.2b core)

Suggest suitable purification techniques given information about the substances involved (2.2b core)

Learning Objectives

Simple distillation is used to separate water from a dissolved solid

Fractional distillation is used to

separate a more volatile liquid from a

less volatile liquid in the mixture

Purification of a mixture often

involves a variety of methods, e.g.

separating sand from salt Suggested Teaching Activities

Introduce simple distillation by referring to differences in boiling points of solids and liquids.

Introduce idea of simple distillation with demonstration experiment (see below).

Link this in with the use of simple distillation for producing drinking water from salt water as done in several places in the Middle East.

Remind students about ease of evaporation and boiling points. Get students

to suggest which of a pair of liquids in a mixture will evaporate first when heated.

Demonstrate fractional distillation or show a video clip of fractional distillation. Link this with production of ethanol for a solvent, use in alcoholic drinks, such as whisky, and for the production of fragrances.

Extension and Consolidation

More advanced students could find out about desalination plants and membrane cells. They could research the internet for examples of membrane cells and desalination plants in outline and discuss the economic and environmental reasons for adoption of these processes.Extension work could include discussion of steam distillation for producing oils for perfumes.

Learning Outcomes

Describe how distillation is used to

purify mixtures of liquids

Describe some applications of

distillation

Suggest appropriate methods to

purify a given mixture of substances


Demonstrate simple distillation of water from copper(ii) sulfate to leave concentrated solution of copper(ii) sulfate in flask. This can be simply done by students by boiling copper(ii) sulfate solution in a hard glass boiling tube connected to an L-shaped delivery tube which is cooled by a damp cloth. Demonstrate (partial) separation of ethanol from water, especially if a fractional distillation column is available (see Chemistry for IGCSE, p.15). The ethanol can be collected and its flammability tested.

Pictures/ video clips of perfume production using distillation could be shown, e.g. lavender oil, orange flower oil.

Chemistry for IGCSE, 12.1 The Periodic Table, p.146 (S refers to material in the supplement)Approximate timing for this section: 30 minutes (or less depending on previous experience)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the Periodic Table as a method of classifying elements (9 core) Describe the change from metallic to non-metallic character across a period (9.1 core)

Learning Objectives

Elements are arranged in the Periodic

Table in order of their proton number

Metallic character decreases across a

period but increases down a group

Know the position of some elements

and groups, e.g. alkali metals,

halogens and noble gases, in the

Periodic TableSuggested Teaching Activities

This section serves as an introduction / reintroduction to the Periodic Table to remind the students of its structure and its use in classifying the elements.

Start by giving students labelled samples of selected elements, if available (or pictures of these) so that they become familiar with their character as solids, liquids or gases.

Giving a historical background to the Periodic Table helps emphasise the difficulty of the problems involved.

Use the version of the Periodic Table in the syllabus. Large coloured versions are more useful, especially those with pictures of the elements. Students could make observations from a photographic version of the Periodic Table.

Get students to annotate their own blank copies of the Periodic Table using shading and a key to show metals and non-metals and the step transition between the two.Concentrate at his stage only on the names of selected elements, the way the Periodic Table is arranged and the names of the major groups (alkali metals, halogens, noble gases) as well as the metalnon-metal transition and which elements are liquids and gases. Extension and Consolidation

Ask groups of students to research different elements especially Group I and VII and 0 and transition elements and report back to the class on what they have found. This could also be set for homework.

Students could product fact cards to show proton number and neutron number in preparation for next lesson cards. The cards could be compared and trends shown. A database of properties and states for elements could be set up. Students could suggest relevant questions to find the metals, solids, liquids etc and enter their results on a blank copy of the Periodic table.

Learning Outcomes

Describe the arrangement of the

elements in the Periodic Table

Describe how the metallic and non-

metallic character of the elements

changes across a period Be able to name and give examples

of the alkali metals, halogens and

noble gasesPractical Work and Resources

Periodic Table with pictures of elements.

Selection of elements or pictures of the elements.

Web Periodic Tables to investigate limited range of properties of elements.

Chemistry for IGCSE, 2.1 Inside the atom, pp. 1819 (S refers to material in the supplement)Approximate timing for this section: 25 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) State the relative charges and the approximate relative masses of protons, neutrons and electrons (3.1 core) Define proton number and nucleon number (3.1 core)

Use proton number to explain the structure of the Periodic Table (3.1 core)

Learning Objectives

An atom is the smallest uncharged

particle that can take part in a

chemical change

The subatomic particles are protons

and neutrons in the nucleus and

electrons in shells outside the nucleus

Know the charges and relative

masses of the proton, neutron and

electron

Atoms are neutral because the

number of positive protons equals the

number of negative electrons

Atoms are arranged in the Periodic

Table in order of their proton numberSuggested Teaching Activities

Ask students what they think about the structure of the atom. They may think that they are like hard balls. Introduce the structure of the atoms as a central nucleus surrounded by rings of electrons, but draw to students attention that scientists are not sure where the electrons actually are in space; a better model is to show that electrons are arranged in a complex three-dimensional way in space. However students should realise that it is convenient to draw the electrons as behaving like a planetary system.

The size of the nucleus compared with the diameter of the atom might be compared with the size of a lemon pip compared with that of a football field.

The importance of proton number in the arrangement of the elements in the Periodic Table might then be discussed.Extension and Consolidation

Look at different models of the atoms through the ages e.g. hard balls, plum pudding model, planetary model , modern model and put these in historical context of the discovery of various types of particle and development of new theories.The size of the various atoms might also be discussed and patterns in the size related to the position in the Periodic Table.

Learning Outcomes

State the relative mass and charge of

a proton, neutron and electron

Define proton number and nucleon

number

Use proton number to explain the

basis of the Periodic Table


Model of atom showing various shells.Video clips or simulations of structure of atoms showing moving electrons.

Chemistry for IGCSE, 2.2 Isotopes, pp. 201 and Energy from radioactivity, p.89 (S refers to material in the supplement)Approximate timing for this section: 30 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Define isotopes (3.1 core) State the two types of isotope as being radioactive and non-radioactive (3.1 core)

State one medical and one industrial use of radioactive isotopes (3.1 core)

Describe radioactive isotopes such as U-235 as a source of energy (6.2 core)

Learning Objectives

The number of protons + nucleons in

the nucleus is called the nucleon

number

The number of neutrons in an atom is

found by subtracting the proton

number from the nucleon number

Isotopes are atoms with the same

number of protons but different

numbers of neutrons

Isotopes can be radioactive or non-

radioactive

Know one medical and one industrial

use of radioisotopes

Uranium-235 is a radioisotope that is

a source of energy in atomic power

Suggested Teaching Activities

Before discussing uses of isotopes it is important to discuss the general idea of isotopes as being described as non-radioactive as well as radioactive. Examples could be given of writing the isotopes in standard form showing nucleon number as well as atomic (proton) number. Filling in the gaps in tables showing numbers of neutrons, electrons and protons in given isotopes gives students plenty of practice in understanding atom structure.

The uses of isotopes can be shown using video clips, sources from the internet or from books. Students could research the use of one industrial and one medical use and feed back to either small groups or to the whole class.

Details about alpha, beta and gamma radiation are not required.

The use of isotopes of uranium in the production of energy can be discussed in terms of perceived problems about nuclear fuels, but that they are non-polluting in terms of minimal carbon dioxide production. Extension and Consolidation

Finding out about the range of isotopes and types of radiation.Students could hold a discussion or a mock meeting about the pros and cons of building a nuclear power station in a rural area near the sea. Some students could represent the contractor, nuclear authority and government department of energy, others could represent worried local residents, pressure groups etc.

Learning Outcomes

Define the term isotope State the difference between

radioactive and non-radioactive

isotopes

State some industrial and medical

uses of isotopes

Describe the use of specific

radioactive isotopes as a source of

energyPractical Work and Resources

Video clips about uses of non-radioactive and radioactive isotopes.Leaflets / information from internet about nuclear fuels and nuclear power.

Chemistry for IGCSE, 2.3 Electronic structure and the Periodic Table, pp.223 (S refers to material in the supplement)Approximate timing for this section: 30 minutes (if the activity is done)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the build-up of electrons in shells and understand the significance of the noble gas electronic structures and of valency electrons (3.1 core) Use the simple structure of atoms to explain the basis of the Periodic Table (3.1 core)

Learning Objectives

Electrons in atoms are arranged in

shells

The outer shell electrons in an atom

are the valency electrons

The number of valency electrons in

an atom of an element determines the

chemical properties

Atoms of elements in the same group

in the Periodic Table have the same

number of valence electronsSuggested Teaching Activities

Students already know that the number of electrons in a neutral atom equal the number of protons. Here they build up a picture of the atoms in shells for the first 20 elements.

Start by giving the rules for the build-up of electrons in shells together with the concept of full shells of electrons. Students can then draw the electronic structure of particular atoms in empty shells and arrange them on a blank Periodic Table according to the proton number. Alternatively, they could be given the electronic structure of the first 20 elements and asked to arrange them to find the periodic pattern out for themselves.

From the general arrangement so discovered emphasise that the number of valency electrons is the same as the group number. Then go on to draw out similarities of chemical / physical properties of elements in some groups of the Periodic Table, e.g. Groups I, II, VII and 0.

Finish off by discussing the relationship between the unreactivity of the noble gases and their electronic structure. Extension and Consolidation

Less able students could be given the task of making model atoms using different coloured circles of cards representing the electron shells and circle of white sticky dots to represent the electrons. Each student does one, two or three of the first 20 elements. They then come out to the board and place the atom they have made in the appropriate place on a blank Periodic Table (using sticky tape).

Learning Outcomes

Describe the build-up of electrons in

shells

Explain the significance of the noble

gas electronic structure and valency

electronsPractical Work and Resources

Blank Periodic Tables. Photocopied empty electron shells for students to fill in.

Chemistry for IGCSE, 2.4 Elements, compounds and mixtures, pp. 245 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (if demonstrations included and models made)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the differences between elements mixtures and compounds (3.2 core)

Learning Objectives

An element contains only one type of

atom

A compound is a substance

containing two or more different

atoms bonded together

Mixtures do not have a fixed

composition and their components

can be separated by physical means Suggested Teaching ActivitiesShow models of elements with different numbers of atoms, e.g. sulfur, chlorine, nitrogen, carbon, and ask students what they notice about each. From this develop the definition of an element.Demonstrate the difference between elements and compounds by experiment, comparing the properties of, e.g., sodium and chlorine with sodium chloride or iron and sulfur with iron sulphide (see experiments below).

From this develop the concept of a compound.

Students could make models of compounds using model kits, or using clay or Plasticine of different colours and straws or cocktail sticks. It is best to stick to models of simple molecular structures at this stage.

Finish off by discussing. Extension and Consolidation

Students could look at models of selected compounds on appropriate DVDs or on the internet. Pictures of compounds which are able to be rotated are useful to give a three dimensional representation and show students that there are a variety of different shapes of simple molecules

Learning Outcomes

Define the terms element and

compound Explain the differences between

elements, compounds and mixturesPractical Work and Resources

Demonstration of burning sodium in chlorine to compare the properties of the elements with that of the compound sodium chloride (see Chemistry for IGCSE, p.25).Demonstration of difference between iron, sulfur and iron sulphide. The sulphide is dark brown and reacts with acid to give off a gas which turns lead ethanoate paper grey-brown: demonstrate using a fume cupboard since the hydrogen sulfide is very poisonous. Sulfur does not react with acid, but iron gives off hydrogen (although there are small amounts of hydrogen sulfide from impurities in the iron).

Chemistry for IGCSE, 2.5 Metals and non-metals, pp. 267 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (if demonstrations or class experiments included)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the differences between metals and non-metals (3.2 core)

Learning Objectives

Metals are good conductors of heat

and electricity and are malleable,

ductile and shiny

Non-metals are poor conductors and

are brittle and often dull

Many metals, but not all, have high

melting points

Exceptions are graphite (non-metal

which conducts) and Group I metals

and mercury (low melting points) Suggested Teaching ActivitiesIf sufficient strips of metal are available, students could investigate some of their properties such as electrical conductivity, flexibility and hardness by scratching. These may be compared with selected non-metals, e.g. sulfur.

The ideas of a fair test could be mentioned in relation to this experiment.

The idea of physical as opposed to chemical properties could be introduced here.

This is also an appropriate place to introduce ideas about density. Students could compare the densities of some metals and non-metals using tables of data.When a list of general physical properties of metals and non-metal has been produced, some exceptions to the rule might be demonstrated e.g. graphite, mercury.

The chemical properties of metals could also be mentioned briefly here, e.g. reaction with water, steam and dilute acids. These will however be covered in detail later.Extension and Consolidation

Students could compare the density of blocks of different metals, e.g. iron, aluminium, and tin, to see the range of densities. Irregular pieces of metal may have their volumes calculated by displacement of water.The hardness of metals could be compared by seeing which metals are able to scratch others.

They could search the internet to compare selected properties of a given set of metals and non-metals.

Learning Outcomes

Describe the differences between

metals and non-metals

Recognise that some metals and non-

metals have properties that are

exceptions to these general rulesPractical Work and Resources

Class practical or demonstration: comparing electrical conductivity of metals and non-metals (see Chemistry for IGCSE, p.26); suitable non-metals are sulfur and iodine (demonstration only). If lead is chosen as a metal, it should be place inside a transparent polythene bag. Students should wash their hands after the experiment. The flexibility of the metals could also be tested and ideas of a fair test brought up.

Video clips of metals and non-metals undergoing testing for strength or other properties.

Chemistry for IGCSE, 3.1 Ionic bonding, pp. 3031 (S refers to material in the supplement)Approximate timing for this section: 40 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the formation of ions by electron loss or gain (3.2a core)

Describe the formation of ionic bonds between elements from Groups I and VII (3.2a core) Describe the formation of ionic bonds between metallic and non-metallic elements (3.2a supplement)

Learning Objectives

When atoms from Groups I and VII

react, the atoms from the Group I

element loses the electron from its

outer shell and the atom from the

Group VII element gains this electron

Ions have the noble gas electronic

structure with a complete outer shell

of 8 electrons (or 2 for lithium)

Know how to draw dot and cross

diagrams to show the electronic

structure of ions between Group I

and VII elements

The attraction between oppositely

charged ions is called ionic bonding Know how to draw dot and cross

diagrams for ionic compounds with

multiple charges (S) Suggested Teaching Activities

Refer back to the experiment where sodium reacted with chlorine to ask what was happening when the reaction occurred. Introduce the idea that it is only the outer electrons that move when reactive metals react with reactive non-meals. A demonstration using small circular fridge magnets can be quite successful (outer electron shells only). There is also an opportunity to demonstrate the movement of the electron(s) with a kinaesthetic activity. There is no attempt at this stage to mention giant ionic structures.

Students practise drawing the ions formed from suitable elements showing the electron shells and overall charge.From ions with simple charges, the structure of ions with multiple charges may be accessed. Extension and Consolidation

Models of ionic structures can be built, so that the idea of giant structures is introduced concomitantly with the idea of ions and students do not get the impression that ions normally exist just as pairs.

Learning Outcomes

Describe the formation of positive

and negative ions

Draw dots and cross diagrams for

ions of Group I and Group VII

elements Draw dot and cross diagrams for

other ions including those with

multiple charges (S)Practical Work and Resources

Show video clips of atoms turning into ions or a computer simulation of this.Computer simulations to show the formation of ions from atoms can be shown.

Small fridge magnets to demonstrate the movement of the electrons.

Chemistry for IGCSE, 3.2 and 3.3 Covalent bonding (1) and (2) more complex molecules, pp. 325 (S refers to material in the supplement) Approximate timing for this section: 50 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the formation of single covalent bonds in H2, Cl2, H2O, CH4 and HCl as the sharing of pairs of electrons leading to the noble gas configuration (3.2b core) Describe the electron arrangement in more complex covalent molecules such as N2, C2H4, CH3OH and CO2 (3.2b supplement)

Learning Objectives

A covalent bond is formed when

atoms share a pair of electrons

When atoms combine to form

covalent bonds each atom has 8

electrons in its outer shell (except for

hydrogen which has 2)

A single covalent bond is shown by a

line, e.g. HH


diagrams for the molecules specified

in the core: H2, Cl2, H2O, CH4 and

HCl

Know that a double covalent bond

contains 2 pairs of shared electrons

and a triple bonds contains 3 (S)


diagrams for more complex

molecules, e.g. N2, C2H4, CH3OH and CO2 (S)Suggested Teaching Activities

Refer back to ball and stick models made earlier to introduce the idea that covalent bonding involves the sharing of pairs of electrons. A demonstration using small circular fridge magnets can be quite successful (outer electron shells only). Alternatively you can use different coloured counters or sticky paper circles. There is also an opportunity to demonstrate the movement of the electron(s) with a kinaesthetic activity.

Give examples of the types of atom that join to form covalent compounds, so that students get the idea that it is usually non-metals which combine here.

Students practise drawing the molecules formed from suitable elements, starting with the formation of single-bonded compounds only.

After this, students could go on to draw structures with more than two types of atom and then with double and triple bonds.Extension and Consolidation

Less able students could omit making dot and cross diagrams involving double and triple bonds. They can concentrate more on the ideas of pairing up the molecules using different coloured counters and ignoring the inner shell electrons.

Learning Outcomes

Describe the formation of covalent

bonds

Draw dot and cross diagrams for

hydrogen, chlorine, water, methane

and hydrogen chloride

Describe the electron arrangement in

covalent molecules with three or

more different types of atom (S) Describe the electron arrangement in

atoms containing double or triple

bonds (S) Practical Work and Resources

Show video clips of atoms combining to form molecules or a computer simulation of this.

Small fridge magnets to demonstrate the movement of the electrons to form shared pairs.

Chemistry for IGCSE, 3.4 Ionic or covalent?, pp. 367 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (including practical)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the differences in volatility, solubility and electrical conductivity between ionic and covalent compounds (3.2b core)

Describe the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions (3.2a supplement)

Learning Objectives

Ionic compounds generally have high

melting points, dissolve in water and

conduct electricity in solution Covalent compound generally have

low melting points, are insoluble in

water and so do not conduct

electricity

Know the meaning of the term ionic

lattice (S)Suggested Teaching ActivitiesStudents could start by looking at ionic crystalline structures with a hand lens or microscope to show the regularity of crystal structure. The question could then be asked about why these crystals are so regular. This leads into ideas about the structure of an ionic crystal lattice. This can be developed naturally out of the students knowledge about ionic bonding.

Models of the ionic structure could be shown at this point.

The question then arises as to what is the generalised difference between molecular and ionic compounds. This can be undertaken experimentally by students seeing how a range of ionic and molecular compounds behave on melting, dissolving in water and conducting electricity. Some molecular compounds are soluble in water, e.g. glucose (but mention there are exceptions). The point is that even if they do dissolve, they will not conduct. Students could undertake a data search concentrating on melting and boiling points of a range of ionic and covalent compounds, e.g. chlorides and oxides. The dissolving and subsequence conductance of electricity due to the movement of ions can be shown by means of computer simulations or by using counters marked with + and for the ions. It is also possible to do a kinaesthetic activity with some students being ions and others water molecules, freeing them from the surface of the crystal.

The point should finally be made that molecular structures cannot conduct because they have no charged particles. Extension and Consolidation

It is useful to demonstrate ionic conduction by carrying out electrophoresis experiments. This demonstration makes it clear to the students that it is the ions which move through the solution and not the electrons. It can be done with damp filter paper on a microscope slide attached to a 20 V power pack by wires and crocodile clips. A crystal of potassium(vii) manganate or copper(ii) sulfate is placed in the middle of the filter paper. After a while, the coloured ions are seen moving to one of the electrodes. Copper ions may be made more visible by adding aqueous ammonia to the filter paper. The electrophoresis of copper chromate in concentrated aqueous urea in a U-tube, with carbon electrodes dipping into sulfuric acid layered over the chromate in each arm, shows the movement of copper ions to the cathode and chromate ions to the anode.

Learning Outcomes

Describe the differences

in volatility, solubility and electrical

conductivity between ionic and

covalent compounds

Explain the term ionic lattice (S)Practical Work and Resources

Compare how easily ionic and molecular substances melt and conduct electricity in solution (see Chemistry for IGCSE, p.36). Suitable substances to use are sulfur, iodine, glucose and wax (carry out in fume cupboard) and sodium chloride, anhydrous copper sulfate and potassium chloride (which will not melt easily). If an electrical conductivity metre is available, this can be used to measure the electrical conductance in solution.

Chemistry for IGCSE, 3.5 Giant covalent structures, pp. 389 (S refers to material in the supplement)Approximate timing for this section: 50 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the giant covalent structures of graphite and diamond (3.2c core)

Relate their structures to the use of graphite as a lubricant and of diamond in cutting (3.2c core) Describe the macromolecular structure of silicon(iv) oxide (silicon dioxide) (3.2c supplement)

Describe the similarity in properties between diamond and silicon(iv) oxide related to their structures (3.2 supplement)

Learning Objectives

Diamond and graphite are

macromolecules

Describe the structures of diamond

and graphite

Know that graphite is a lubricant

because the layers slide over each

other

Know that diamond is used in cutting

because it has a 3-dimensional

network of strong bonds

Know why graphite conducts

electricity (S) Know the structure of silicon(iv)

oxide and compare its structure and

properties with diamond (S)Suggested Teaching Activities

If samples of natural graphite are available, students could feel the slippery surface and demonstrate how easily it flakes and can mark paper. A comparison could then be made with photographs or video clips of diamond, showing that it is very hard.

Now tell students these are both forms of carbon with very different properties. How can we account for this?Show students models or pictures of the structures and properties (high melting point etc.) of the two allotropes. Students can then try to work out for themselves why diamond is hard and graphite is soft and flaky. The most useful diagrams show the 3-dimensional structure which is rotatable on a computer simulation.

The electrical conductivity of graphite can then be explained in terms of the mobile electrons moving through the layers this conduction could be demonstrated.

Give students cards showing different properties of diamond and graphite and their explanations, and ask them to work out which property fits which explanation e.g. diamond is denser than graphite atoms in diamond matches with the atoms are closer together.The structure of silicon dioxide can then be discussed start with the premise that sand is largely silicon dioxide and that it does not conduct electricity. The similarity to diamond and the differences could then be discussed. Extension and Consolidation

The structure and properties of carbon allotropes could be extended to other forms of carbon, i.e. buckminsterfullerene and nanotubes. Other forms of silicates could be mentioned and the fact that silicates are glasses. Students could be asked why some forms of glass appear to conduct electricity when semi-molten; this could be demonstrated with a suitable sample of glass. This leads to the idea that there are ions in glass which, when it is semi-molten, can move.

Learning Outcomes

Describe the structures of graphite

and diamond

Relate the uses of graphite and

diamond to their structures

Describe the structure of silicon(iv)

oxide (S) Relate the properties of diamond,

graphite and silicon dioxide to their

structures (S)Practical Work and Resources

Show computer-generated pictures of graphite and diamond.Video clips of diamond-tipped drills being used for cutting.

Demonstrate that a pencil lead conducts electricity.

Chemistry for IGCSE, 3.6 Metallic bonding, pp. 401 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (including practical demonstrations)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe metallic bonding as a lattice of positive ions in a sea of electrons and use this to describe the electrical conductivity and malleability of metals (3.2d supplement)

Learning Objectives

The atoms in metals are arranged in regular layers (S)

A metallic structure consists of positive metal ions in a sea of electrons (S) Metals conduct electricity because the mobile sea of electrons can move freely through the structure (S) Suggested Teaching Activities

Start by getting students to reiterate the properties of metals.

Introduce the idea of metal structure by reference to metal crystals or grains. These can be seen, for example, on lamp posts and can be demonstrated by making an etching lead pancake (see below).Since metals have crystal structures, by analogy with ionic structures their atoms may be regularly arranged in layers. A demonstration of metal structure using a bubble raft could be shown (see below).Show a model of metal structures with layers of polystyrene spheres, and use the sliding of these layers to explain the malleability and ductility of metals.

Develop the metal cations in a sea of electrons model. Develop the model to show that the outer electrons have been lost, i.e. the ions are not touching. The electrons can then move through the structure when a voltage is applied. Extension and Consolidation

Metal crystals can be grown using displacement reactions, e.g. a copper wire dipping into a solution of silver nitrate.

Learning Outcomes

Describe metallic bonding (S) Explain the electrical conductivity

and malleability of metals (S)Practical Work and Resources

The crystal structure of metal can be shown by making an etched lead pancake: Melt a small amount of lead in a crucible. When it is molten, pour out the lead onto a flat surface to get a lead pancake. Immerse this in dilute sulfuric acid. After 2030 minutes remove the lead and observe the crystal structure.

A model of metallic structure can be demonstrated using a bubble raft. All the class can easily see this if it is carried out on an overhead projector (Chemistry for IGCSE, p.40).

Chemistry for IGCSE, 13.1 Alloys, pp.1589 (S refers to material in the supplement)Approximate timing for this section: 40 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets)

Describe an alloy, such as brass, as a mixture of metal with other elements (3.2 core)

Explain why metals are often used in the forming of alloys (10.1 core)

Identify representations of alloys from diagrams of structure (10.1 core)

Learning Objectives

Alloys are mixtures of metal atoms

with other metal atoms or non-metal

atoms

Know how to identify an alloy from

a diagram of its structure

The properties of metals are changed

by making it into an alloy

Metals are made into alloys to

improve their strength, hardness or

resistance to corrosionSuggested Teaching Activities

Introduce the idea of alloys as mixtures by reference to diagrams of their structure. By reference to larger or smaller atoms within the main metal, students should be able to see that the layers are prevented from sliding over each other. This can be modelled by polystyrene layers with several of the spheres increased in size by addition of Plasticine. Students should be able to see that the layers are prevented from sliding.

Students research properties of alloys compared with constituent elements.The difference in properties of alloys compared with the individual metals in their composition can be studied by reference to solder (see below).

Finish by mentioning that many alloys reduce corrosion. This can be taken further when rusting and corrosion is discussed later.Extension and Consolidation

Students could research the properties of alloys for homework or select particular alloys to study and feed back to groups or the whole class. Students could also ensure that they can draw accurate representations of alloys with the layers distorted compared with the layers in pure metals.

Learning Outcomes

Describe the general physical and

chemical properties of metals

Explain why metals are often used in

the forming of alloys

Identify representations of alloys

from diagrams of their structurePractical Work and Resources

Demonstrate the lower melting point of solder compared with tin and lead, by carrying out an experiment to demonstrate the order in which these three metals melt (see Chemistry for IGCSE, p.158).

Video clips about alloys and computer simulations about why alloys are stronger than pure metals could be shown.

Chemistry for IGCSE, 6.7 Conductors and insulators, pp. 823 (S refers to material in the supplement)Approximate timing for this section: 25 minutes (without practical work)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the reasons for the use of copper and (steel-cored) aluminium in cables and why plastics and ceramics are used as insulators (5 core)

Learning Objectives

Steel-cored aluminium cables are

used in HT power lines because

aluminium is lightweight as well as a

good conductor and steel strengthens

the cable

Copper is used in electrical wiring

because it is a good conductor of

electricity

Insulators, such as plastics and

Ceramics, prevent an electric current

from flowing: they are non-

conductorsSuggested Teaching ActivitiesShow a variety of conductors and insulators (including clay, cements, sand, porcelain and plastics described as solid inorganic non-metallic materials). The term insulator can be explained in terms of electrical resistivity. A link can be made back to the structure of silicon(iv) oxide as an insulator.

Show photographs of HT electricity pylons, focussing on the ceramic insulators and on the cables. A discussion can then ensue on the properties required for carrying electricity by over-ground cables (strength and low density as well as good electrical conductivity).

Students could select the best metals to use for electrical cables over- ground and underground from selected tables of data about particular metals and alloys. Finish off by discussing the use of plastic-coated copper wires for domestic electricity and why they must not be subjected to current overload.


Demonstrate the non-conduction of clays and ceramics compared with the conduction of metals.For more advanced students, the effect of increasing the temperature on the passage of electricity through wires could be mentioned (in terms of increased vibration of metal ions).

Learning Outcomes

Describe reasons for the use of steel-

cored aluminium in high voltage

electric cables and copper in

electrical wiring

Describe plastics and ceramics as

Insulators Explain why plastics and ceramics

are insulators (S)Practical Work and Resources

If a resistivity meter is available, the resistance of various conductors and insulators can be measured.

The comparative conductance of various materials can be compared using the apparatus shown on Chemistry for IGCSE, p.82, especially if this apparatus was not used when the properties of metals were discussed earlier on.

Chemistry for IGCSE, 4.1 Chemical formulae, pp. 445 (S refers to material in the supplement)Approximate timing for this section: 30 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Use the symbols of the elements and write the formulae of simple compounds (4 core)

Deduce the formula of a simple compound from the relative numbers of atoms present (4 core)

Learning Objectives

Know the chemical symbols for the

elements stated in the syllabus

Know how to name compounds

containing two elements

Know how to work out the formula

of a simple compound from valencies

(combining powers) Suggested Teaching Activities

You could start in the context of an historical introduction as to why symbols are important. Stress that if a symbol has a second letter that is always small. The Periodic Table can be used in conjunction with a discussion of element symbols to give students more experience in determining the position of elements in relation to each other.

Revise concept of valency / combining powers.

Go over naming of compounds with two elements and stress how the name ending changes when a compound is formed from two elements.

Students can test themselves with flash cards in two piles, one with the element / compound names and one with the symbols/ formulae. This could be done as a competition, the first group to finish all the cards correctly being the winners.


More advanced students could research the origins of some of the symbols of the elements. Core students could concentrate more on the names of the elements and compounds.

Learning Outcomes

Know how to write symbols for

chemical elements and formulae for

simple compounds

Deduce the formula of a simple

compound from the relative number

of atoms presentPractical Work and Resources

Samples of pictures of various elements and compounds to relate to symbols / formulae.

Chemistry for IGCSE, 4.2 Working out the formula, pp. 467 (S refers to material in the supplement)Approximate timing for this section: 50 minutes (including model making)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Deduce the formula of a simple compound from a model or diagrammatic representation (4 core) Determine the formula of an ionic compound from the charges on the ions present (4 supplement)

Learning Objectives

Know how to work out the formula

of an ionic or molecular compound

from a diagram Know how to work out the formula

of an ionic compound from the

charges on its ions (S)Suggested Teaching Activities

Students could start by working out the molecular and the empirical formulae from relatively simple molecular structures, e.g. P4O10. These could be provided as models or as diagrams/ downloads from the internet. Organic structures can also be included to widen the students appreciation of the range of molecules.

Students can be asked to write the full structural formulae (displayed) for molecular compounds, by considering the combining power of particular atoms.

Now introduce how to work out the formulae for giant covalent structures including ionic structures. The ionic structures should be of the sectional type not of the three-dimensional type.

More advanced students can go on the predict formulae from the charges on the relevant ions. The formula of the ions should be linked to the group number in the Periodic Table.Extension and Consolidation

More advanced students could try to write formulae for compounds with a greater range of ions e.g. phosphate, hydrogencarbonate, sulphite, nitrite.They could also try to build models of more complex structures.

Learning Outcomes

Be able to work out the chemical

formula of an ionic or molecular

compound from a diagram of its

structure

Be able to work out the formula of an

ionic compound by using the

charges on its ions (S)Practical Work and Resources

Models of compounds to calculate the formula from or downloaded molecular structures from the internet, e.g. Wikipedia, often give the structure of more complex molecules. Model kits to make models of selected structures or for students to investigate the formulae of pre-made structures.

Chemistry for IGCSE, 4.3 Chemical equations, pp.489 (S refers to material in the supplement)Approximate timing for this section: 60 minute (including model making and practical demonstrations)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Construct word equations and simple balanced chemical equations (4 core) Deduce the balanced equation for a chemical reaction given relevant information (4 supplement)

Learning Objectives

There is the same number of each

type of atom on each side of a chemical equation

In a chemical reaction, the mass of

the products is equal to the mass of

the reactants

To know how to write word

equations

To know how to balance simple

symbol equations by placing

numbers in front of particular

reactants or products Deduce a balanced chemical

equation given relevant information

(S)Suggested Teaching Activities

Start with ideas about reactants and products and perhaps carrying out selected chemical reactions. Word equations can then be introduced. Start with molecular examples so that the students have a clear picture of what the equation means.

Students could build model reactions of a molecular type, e.g. hydrogen reacting with chlorine to form hydrogen chloride. They could break the bonds in the reactants and form the new products. This leads to the idea that the number of atoms in the products is the same as in the reactants and hence there is conservation of mass (see experiments below).Students could then do more formal balancing of equations (including those involving ionic compounds), perhaps using the dot method for keeping account of the number of atoms in a sequential fashion as shown in Chemistry for IGCSE, p.49. More advanced students can go on to balance equations for compounds where use of brackets is involved.

If computer access is available, students could use suitable websites or CD ROMs to test their ability to balance equations. Extension and Consolidation

Making a flickbook of reactions showing reactants going into products helps to counteract the static impression given by an equation. This could be set for homework or could be additional work for core students. Core students could also concentrate more on model building.More advanced students can be given more complex examples of equations to balance.

Learning Outcomes

Construct word equations

Balance simple symbol equations

when given the chemical formulae of

some or all of the species in the

equation

Construct balanced symbol equations

when given suitable information (S)Practical Work and Resources

Demonstration of reactions to discuss the meaning of reactants, products and to discuss the conservation of mass, e.g. magnesium burning in air/ oxygen, reaction of zinc and iodine, reaction of iron and sulfur. For some reactions you could demonstrate that there is no mass change, e.g. adding sodium hydroxide pellets to a concentrated solution of iron(ii) chloride and shaking to dissolve the pellets. Some discussion could then be involved about why there is an apparent mass change when magnesium burns in air, the air having mass. The idea could be extended to the need to measure the mass of gases as well in reactions where these are evolved e.g. acid and carbonate.

Chemistry for IGCSE, 4.4 More about equations, pp. 501 (S refers to material in the supplement)Approximate timing for this section: 40 minutes

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Construct equations with state symbols including ionic equations (4 supplement)

Learning Objectives

The correct use of the state symbols

(s), (l), (g) and (aq) in equations (S) Ionic equations considered as

simplified symbol equations, showing only those ions which react and the products of their reaction (S) The ions which do not take part in a

reaction are called spectator ions (S)Suggested Teaching Activities

Ionic equations can be introduced through experimental work / demonstrations (see below). This has the advantage that students can reinforce their observational skills.

Start with simple examples where a precipitate is formed by adding two solutions together, then graduate to more complex examples e.g. reaction of acid with carbonate, reaction of chlorine with potassium iodide.


Core students could also study the use of state symbols. They could use them to reinforce the state of particular substances they are likely to come across in the course. They can do this given suitable information and simple equations.

Learning Outcomes

Write symbol equations to include

state symbols (S)

Construct balanced ionic equations

(S)Practical Work and Resources

Demonstrate a precipitation reaction to introduce the idea of ions combining e.g. copper(ii) sulfate + sodium hydroxide.Demonstrate (later) reaction of aqueous chlorine with aqueous potassium iodide to show a more complex example of an ionic equation.

Chemistry for IGCSE, 11.5 Testing for cations, pp.1401 (S refers to material in the supplement)Approximate timing for this section: 50 minutes (including equation writing and demonstration of the tests)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the following tests to identify aqueous cations: aluminium, ammonium, calcium, copper(ii), iron(ii), iron(iii) and zinc using aqueous sodium hydroxide and

aqueous ammonia (8.4 core)

Learning Objectives

The use of aqueous sodium

hydroxide and aqueous ammonia to

test for the cations specified above to

include the colour of the precipitate

where appropriate

When sodium hydroxide is heated

with a solution containing

ammonium ions ammonia gas is

produced Suggested Teaching Activities

The analysis of aqueous cations follows directly from the point where students have learnt how to write equations. This has the advantages that students can be encouraged to make observations early on in the course as well as giving them an early opportunity to write equations for some of the reactions. These tests can be referred back to later on in the course for reinforcement, e.g. test for transition element ions when transition elements are discussed, test for ammonium ions in relation to fertilisers.

Some of the tests can be demonstrated, but it is best if some are conducted by the students themselves using very small amounts of materials.Students can also be asked questions relating to a scheme to separate out ions or questions of a more demanding nature, e.g. How can you use sodium hydroxide to distinguish whether the sample of an alloy has zinc or copper or both in?

Flash cards can also be used to test students on their knowledge of these tests. Extension and Consolidation

This can be made more challenging by using unknown samples of an ionic compound, or even a mixture or compound where cation and anion have to be tested.More advanced students could research more modern methods for identifying ions.

Learning Outcomes

Describe test for the following ions

in aqueous solution using aqueous

sodium hydroxide or aqueous

ammonia: aluminium,

ammonium, calcium, copper(ii),

iron(ii), iron(iii) and zinc Practical Work and Resources

Test tube experiments on the reaction of aqueous ammonia and sodium hydroxide and the metal ions specified on the left (class or demonstration) including the effect of excess hydroxide and aqueous ammonia (see Chemistry for IGCSE, pp.1401). These experiments can be done using very small amounts of chemicals (a few drops only) on a spotting tile or in an ignition tube.

Demonstrate the reaction of sodium hydroxide with ammonium salts (see Chemistry for IGCSE, p.141).

Chemistry for IGCSE, 11.6 Testing for anions, pp.1423 (S refers to material in the supplement)Approximate timing for this section: 60 minutes (including equation writing if some of the tests are carried out by the students)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Describe the following tests to identify aqueous anions: carbonate (by reaction with dilute acid and then limewater), chloride (by reaction under acidic conditions with

aqueous silver nitrate), iodide (by reaction under acidic conditions with aqueous silver nitrate), nitrate (by reduction with aluminium), sulfate (by reaction under acidic

conditions with aqueous barium ions) (8.4 core)

Learning Objectives

The identification of carbonate,

chloride, iodide, nitrate and sulfate

ions using the tests above Suggested Teaching Activities

The analysis of aqueous cations follows directly from the point where students have learnt how to write equations. This has the advantages that students can be encouraged to make observations early on in the course, as well as giving them an early opportunity to write equations for some of the reactions. These tests can be referred back to later on in the course for reinforcement, e.g. test for carbon dioxide when discussing the decomposition of limestone, the test for sulfates when sulfuric acid is being discussed. Some of the tests can be demonstrated, but it is best if some are conducted by the students themselves using very small amounts of materials.

Stress the importance of writing down the correct observations (i.e. when a carbonate reacts with an acid, bubbles of gas are given off) rather than stating the inference from the observation. It is therefore best to start by allowing the students to undertake the carbonate test themselves and for you to demonstrate some of the others. Flash cards can also be used to test students on their knowledge of these tests.Extension and Consolidation

More advanced students could include the test for bromide ions using silver nitrate. Although not in the syllabus, this has relevance to the photochemical reaction of silver halides in the section on reaction rates.

Learning Outcomes

Describe the tests for chloride and

iodide ions using aqueous silver

nitrate

Describe the test for carbonate ions

using hydrochloric acid and testing

the gas with limewater

Describe the test for nitrate ions

using aluminium foil and sodium

hydroxide then testing the gas with

red litmus paper

Describe the test for sulfate ions

using acidified aqueous barium

chloride or barium nitratePractical Work and Resources

Experiment to test for carbonates (see Chemistry for IGCSE, p.142)

Demonstration of the test for chloride and iodide ions (see Chemistry for IGCSE, p.142)Demonstration of the test for sulfates (see Chemistry for IGCSE, p.143)

Demonstration of test for nitrates (see Chemistry for IGCSE, p.143)

Chemistry for IGCSE, 5.1 Reacting masses, pp. 545 (S refers to material in the supplement)Approximate timing for this section: 40 minutes (including calculations)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Define relative atomic mass, Ar (4 core)

Define relative molecular mass, Mr, as the sum of the relative atomic masses (or relative formula mass for ionic compounds) (4 core)

Calculate reacting masses involving simple proportions (4 core)

Learning Objectives

The relative atomic masses of atoms

are compared on a scale which gives

an atom of carbon-12 a mass of

exactly 12 units

Know how to calculate relative

molecular mass (or relative formula

mass for ionic compounds) as the

sum of the relative atomic masses

Know how to calculate reacting

masses of reactants and products

using simple proportionSuggested Teaching Activities

Weighted models of different atoms could be shown (polystyrene spheres with different masses put in them) to show that the size of the atom is not necessarily related to its mass. From this, go on to explain that a symbol equation shows the number of atoms which react and it is the number which is important.

A number of simple calculations could then be done showing, for example, how many helium atoms weigh the same as one carbon atom. This gets over the fact that if we want to compare numbers of atoms, we have to account for their mass as well.

From here, define relative atomic mass and relative molecular mass.

Give plenty of calculations involving the use of brackets for relative formula mass.


More advanced students could be asked to find out how relative molecular mass is found nowadays. If time needs to be saved, some of the calculations could be done for homework once the pattern has been established.

Learning Outcomes

Define relative atomic mass and

relative molecular mass

Perform simple chemical

calculations involving reacting

masses by using simple proportionPractical Work and Resources

Video clips about counting atoms and relative molecular mass.

Chemistry for IGCSE, 5.2 Chemical calculations, pp. 567 (S refers to material in the supplement)Approximate timing for this section: 40 minutes (including mole calculations)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Define the mole and the Avogadro constant (4.1 supplement)

Calculate stoichiometric reacting masses (4.1 supplement)

Learning Objectives

One mole of a substance contains

6 1023 atoms molecules or ions (S) The Avogradro constant is the

number of specified atoms,

molecules or ions in one mole of a

substance (S)

Using chemical equations and

relative formula masses to calculate

the mass of product obtained from a

given amount of reactant (S)Suggested Teaching Activities

Start by reference to the tiny size and mass of atoms and that we cannot possibly weigh individual atoms. Yet we have to weigh out atoms that are in the correct number so that they react in the correct amounts.

Refer back to the weighing experiment in the last section and develop the idea that you need a lot of particles to weigh things on a balance.

Develop the idea of the mole as a particular number of particles, and then give the formula relating moles to mass and relative atomic / formula mass.

It is important to stress that it should always be clear what the moles refer to. Practise at questions such as How many moles of oxygen atoms are there in 2 moles of sulfur trioxide? help focus students minds on this problem.

Plenty of practice is need not in the basic mole formula which can at this level be regarded as a formula like any other but in the application in calculations, such as finding the mass of product formed from a given amount of reactant. Extension and Consolidation

There is a lot of mythology written about how difficult mole calculations are, much of which is not true. Core students should still be able to do simple mole calculations of the type How many moles of ethanol are there in 5 g of ethanol? The difficult parts are how to apply the mole concept to equations. In place of the mole calculations, core students could be set calculations involving simple proportions as specified on p. 57 of Chemistry for IGCSE. More advanced students could calculate how many atoms of zinc it would be needed to weigh 0.01 g when given the actual mass of an average zinc atom.

Learning Outcomes

Define the mole and the Avogadro

Constant (S) Use the mole in calculations

involving reacting masses (S)Practical Work and Resources

For elements combining, different coloured counters with different masses could be used to represent moles of reactants or products and stoichiometric amounts of these could be weighed to mimic how moles work.

Chemistry for IGCSE, 5.3 How much product? pp. 589 (S refers to material in the supplement)Approximate timing for this section: 50 minutes including calculations (excluding experiment)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Calculate stoichiometric reacting masses involving limiting reagents (4.1 supplement)

Learning Objectives

The limiting reagent is the one that is

not in excess (S) Know how to work out which

reagent is limiting by using the

number of moles of each reagent as

well as the equation for the reaction

(S) Using chemical equations and

relative formula masses to calculate

the mass of product obtained from a

given amount of reactant (S)Suggested Teaching Activities

Limiting reactants can be introduced by way of an experiment with counters along the lines of the diagram on p.58 of Chemistry for IGCSE. Two sets of 10 counters of different colours represent the reactants. The coloured counters are removed in the stoichiometric reacting ratio until only one colour is left. The limiting reactant is the one that is no longer in the pile. This can be repeated using different stoichiometric removal ratios

Calculations of the amount of product obtained from a given amount of limiting reactant can then be undertaken.


More able students could use mole calculations to find the number of moles of water in hydrates copper(ii) sulfate.

Learning Outcomes

Be able to calculate the theoretical

yield of product obtained from a

given amount of reactant (S)

Apply the concept of limiting

reactants (S)Practical Work and Resources

(Extension) Finding the amount moles of water in one mole of hydrated copper(ii) sulfate. A given mass of copper sulfate is heated and the mass of the anhydrous copper sulfate is found. The moles of copper (ii) sulfate can therefore be calculated, knowing its formula. The moles of water are also known by subtraction and the ratio of moles water to moles of copper sulfate calculated.

Chemistry for IGCSE, 5.4 Percentages and volumes, pp. 601 (S refers to material in the supplement)Approximate timing for this section: 90 minutes (if experiments demonstrated as well)

Cambridge IGCSE Syllabus Link (curriculum content numbers in brackets) Calculate stoichiometric reacting masses (4.1 supplement)

Use the molar gas volume, taken as 24 dm3 at room temperature and pressure (4.1 supplement) Calculate volumes of gases (4.1 supplement)

Learning Objectives

Finding the % by mass of an

element in a compound using relative

atomic masses and relative formula

masses (S) The volume of one mole of any gas

is 24 dm3 at room temperature and

pressure (S) For reactions involving gases

calculating reacting masses using the

molar gas volume (S) Suggested Teaching Activities

Students could be introduced to calculations of percentage mass of an element in a compound by a demonstration experiment: finding the percentage by mass of copper in copper(ii) oxide by reducing copper(ii) oxide with natural gas (see details below)

Following on from this, students should be able to extend the calculation to further example

chemistry igcse sow

Documents

terms of particles

particles of liquids

boiling energy

motion of particles

change of state

energy changes

boiling points

able students