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IGCSE Chemistry 0620 Scheme of Work

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IGCSE Chemistry: Electrochemistry and Redox

Whole Unit Overview

(Please note: (S) denotes material in the Supplement (Extended syllabus) only)

Learning Outcomes Suggested Teaching Activi ties Resources

7.3 Define oxidation and reduction in terms of

oxygen loss/gain (see extraction andcorrosion of metals). (Oxidation statelimited to its use to name ions, e.g.iron(II), iron(III), copper(II),manganate(VII), dichromate(VI).)

Link to the reactions of metals (Unit 1 - Periodic

Table 1) and (section 6.2 in Unit 4 OrganicChemistry 1) and halogens (section 9.2 Unit 7 Periodic Table 2).

Experiments possible include reaction ofmetals/non-metals with oxygen and the reactionof metal oxides with carbon.

Link to ideas of the role of redox reactions in the

production of energy from fuels and theextraction of metals. The reactions in carcatalytic converters can also be studied here(link to Unit 2 - Air and Water).

7.3 (S) Define redox in terms of electron transfer. Link this to the reactivity series and reactions ofmetals and metal salt solutions in Periodic Table1, Halogens in Unit 7 and electrolysis later inthis Unit.

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7.3 (S) Identify redox reactions by changes inoxidation state and by the colour changesinvolved when using acidified potassiummanganate(VII)), and potassium iodide.(Recall of equations involving KMnO4 isnot required.)

Demonstrations can include the reaction ofethanol and acidified KMnO4 to yield ethanoicacid (link to Unit 4 - Organic Reactions 1);preparation of chlorine by reaction of conc. HC land KMnO4 solid and reaction of potassiumiodide solution with either chlorine or bromine(link to Unit 7 - Periodic Table 2). Otherreactions which could be demonstrated includezinc +copper(II) sulphate and iodide ions +

hydrogen peroxide.

7.1 (S) Describe the use of silver salts inphotography as a process of reduction ofsilver ions to silver.

A simple experiment can be done with the solidsilver halide salts and sunlight.

Students can make silver chloride, bromide andiodide by precipitation (link to Unit 3 - Acids,Bases and Salts) and watch them changecolour under strong light.

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5 Describe the electrode products in theelectrolysis of

Molten lead(II) bromide

Concentrated hydrochloric acid

Concentrated aqueous sodium chloride.

Between inert electrodes (platinum orcarbon).

These are demonstrations only and link with theproduction of halogens in Periodic Table 2.

The electrolysis of small quantities of aqueoussodium chloride can be safely carried out bystudents. Tests from Unit 3 - Acids, Bases andSalts, can be used to identify all three products.

Link this to the industrial electrolysis of brinelater in this unit.

Students can practice electronic half equationwriting and link this to ideas of redox from earlierin this unit.
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5 Describe the electroplating of metals. Students can electroplate zinc strips withcopper. An initial can be painted onto the stripwith clear nail varnish, to give a silver initial on acopper background.

Aid to electroplating (mainly lists of materials)

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5 (S) Relate the products of electrolysis to the

electrolyte used, exemplified by thespecific examples above together with

aqueous copper(II) sulphate using carbonelectrode and using copper electrodes(as used in the refining of copper).

Awareness of the need for very pure copper forelectrical wiring (pupils can cut open samples ofwire to find copper) due to the interruption of

current flow by impurities.

5 Name the uses of electroplating. e.g. plating cutlery with silver and jewellery withgold or silver.

5 State the general principle that metals orhydrogen are formed at the negative

electrode (cathode), and that non-metals(other than hydrogen) are formed at thepositive electrode (anode).

A demonstration of the electrolysis of leadbromide can be used to set the scheme

Students can electrolyse a range of aqueoussolutions of salts and collect and test electrodeproducts to confirm this.

5 (S) Describe electrolysis in terms of the ionspresent and reactions at the electrodes inthe examples given above.

This links with writing ionic equations (Unit 6 -Amount of Substance).

5 Predict the products of the electrolysis ofa specified binary compound in themolten state.

This should involve metal halides or metaloxides only.

5 (S) Predict the products of electrolysis of aspecified halide in dilute or concentratedaqueous solution.

Demonstrations of the electrolysis of dilute andconcentrated brine can show this.
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10.3(a)(S)

Name the main ore of aluminium

5 Describe, in outline, the manufacture of(i) aluminium from pure aluminium oxidein molten cryolite, (ii) chlorine and sodiumhydroxide from concentrated aqueoussodium chloride. (Starting materials andessential conditions should be given but

not technical details or diagrams.)

Link the production of aluminium back to theproduction of other metals from their ores (Unit1 - Periodic Table 1).

Link to methods of extraction linked to metalreactivity, Unit 1 - Periodic Table 1).

Awareness of the economic and environmentalimplications of the very high energy demand forelectrolysis (link to need for recycling ofaluminium and hydroelectric power).

Awareness of the importance of the products ofthe processes in terms of their uses e.g.chlorine for water treatment, NaOH for making

soap.

5 Describe the reasons for the use ofcopper and (steel-cored) aluminium incables, and why plastics and ceramicsare used as insulators.

The steel core provides additional strength.Aluminium is lightweight and a good conductor.Ceramics are found on pylons carrying hightension (voltage) cables.

6.2 (S) Describe the production of electricalenergy from simple cells, i.e. two

electrodes in an electrolyte. (This shouldbe linked with the reactivity series insyllabus section 10.2 and redox insyllabus section 7.3.)

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6.2 (S) State the use of batteries as aconvenient, portable energy source. Possible issues to discuss include. toxicity of heavy metals used in

batteries and subsequent hazards oftheir disposal.

usefulness of re-chargeable batteriesincluding their use for storage of energyfrom alternative energy sources such as

domestic solar panels and windpowered generators (and in cars).

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