2.2Unit 1 · Inorganic Chemistry
Extraction & uses of metals — Edexcel IGCSE Chemistry Modular - UNIT 1 Revision Notes & Topical Questions
10 min read 7 parts Lesson 2 of 4 1 quiz
Lesson summary
Explain why the extraction method depends on the metal's reactivity.Metals more reactive than carbon are extracted by electrolysis; less reactive ones by heating with carbon.Aluminium is extracted by electrolysis of aluminium oxide dissolved in molten cryolite.CathodeAl3+ + 3e− →…
- Sources of metals
- Extracting iron
- Extracting aluminium
- Using metals
- Common alloys
- Reactivity and oxidation
Section 1 of 7Extraction & uses of metals
1
Sources of metals
Sources of metals most metals occur in the Earth's crust as compounds such as oxides, sulfides and carbonates, in rocks called ores. Very unreactive metals such as gold and platinum occur native (uncombined). Extracting a metal from its compound is a reduction.
2
Reactivity series
The reactivity series (K, Na, Li, Ca, Mg, Al, [C], Zn, Fe, Cu, Ag, Au) predicts the method: a metal below carbon can have its oxide reduced by carbon, e.g. 2ZnO + C → 2Zn + CO2. Metals above carbon hold oxygen too strongly, so electrolysis is needed.
3
Extracting iron
Extracting iron in the blast furnace, coke burns to give heat and CO2, which is reduced to carbon monoxide. CO reduces iron(III) oxide to molten iron. Limestone is added to remove acidic silica impurities as slag.
4
Extracting aluminium
Extracting aluminium bauxite is purified to aluminium oxide, Al2O3.
- Its melting point is over 2000 °C, so it is dissolved in molten cryolite at about 950 °C, saving energy.
- Aluminium ions are reduced at the carbon cathode;
- oxide ions are oxidised at the carbon anodes, which react with oxygen to form CO2.
5
Using metals
Using metals uses follow properties. Aluminium: low density and corrosion resistance → aircraft, drinks cans, power cables (with steel core). Copper: good conductor, unreactive → wiring and water pipes. Iron/steel: strong and cheap → construction.
6
Alloys
Alloys in a pure metal, identical atoms form regular layers that slide easily, so the metal is soft and malleable. Adding atoms of a different size disrupts the layers, making sliding harder, so alloys are stronger and harder.
7
Common alloys
Common alloys steel (iron + carbon), stainless steel (iron + chromium + nickel), brass (copper + zinc, used for fittings and instruments), bronze (copper + tin).
8
Recycling metals saves ores, energy (especially for aluminium) and reduces waste in landfill and mining damage.
9
Reactivity and oxidation
The more reactive a metal, the more easily it is oxidised and the more strongly it holds on to oxygen in its compounds. That is why metals high in the series need the most energy, usually electricity, to extract.
10
Why carbon reduction is cheap
Metals below carbon are extracted by heating with carbon. Carbon (coke) is cheap and also burns to supply the heat needed, whereas electrolysis needs large amounts of costly electricity.
11
A continuous process
The blast furnace runs day and night: raw materials are added at the top and molten iron and slag are tapped off at the bottom. Heating it up from cold takes too much time and energy to stop it often.
12
More uses of aluminium and copper
Aluminium is used for saucepans (good heat conductor) and food cans (non-toxic and resists corrosion). Copper is used for water pipes because it does not react with water, is non-toxic and is easy to bend.
13
Alloy compositions
Mild (low-carbon) steel contains about 0.25% carbon and is soft and easily shaped. High-carbon steel (roughly 0.5–1.5% carbon) is harder, for tools. Stainless steel contains chromium and nickel. Brass is about 70% copper and 30% zinc.
Section 2 of 7Process & sequence
1
Iron ore (haematite, Fe2O3), coke and limestone are added at the top of the blast furnace.
2
Hot air is blown in at the bottom; coke burns: C + O2 → CO2 (strongly exothermic).
3
Carbon dioxide reacts with more coke: CO2 + C → 2CO.
4
Carbon monoxide reduces the ore: Fe2O3 + 3CO → 2Fe + 3CO2.
5
Limestone decomposes: CaCO3 → CaO + CO2.
6
Calcium oxide removes silica: CaO + SiO2 → CaSiO3 (slag).
7
Molten iron and slag sink to the bottom and are tapped off separately (slag floats on iron).
Blast furnacewrite these steps in this order; each step is a marking point.
1
Add ore, coke, limestone
2
Coke burns in hot air
3
CO2 + C → 2CO
4
CO reduces Fe2O3
5
Limestone forms slag
6
Tap molten iron
Section 3 of 7Compare
| Metal | Position | Extraction method |
|---|---|---|
| Potassium, sodium, calcium, magnesium, aluminium | Above carbon | Electrolysis of molten compound |
| Zinc, iron, tin, lead | Below carbon | Heat oxide with carbon (reduction) |
| Copper | Below carbon | Reduction with carbon (purified by electrolysis) |
| Silver, gold | Very unreactive | Found native; physically separated |
| Material | Property | Use |
|---|---|---|
| Aluminium | Low density, resists corrosion (oxide layer) | Aircraft bodies, overhead cables |
| Copper | Excellent electrical conductor, ductile | Electrical wiring |
| Low-carbon (mild) steel | Strong, easily shaped | Car bodies, girders |
| High-carbon steel | Hard but brittle | Cutting tools |
| Stainless steel | Resists rusting (contains chromium, nickel) | Cutlery, surgical instruments |
Section 4 of 7Worked examples
1
Write a balanced equation for the reduction of iron(III) oxide by carbon monoxide and identify what is oxidised.
- Fe2O3 + 3CO → 2Fe + 3CO2.
- Iron(III) oxide loses oxygen (reduced);
- carbon monoxide gains oxygen, so it is oxidised.
- Iron(III) oxide loses oxygen (reduced);
2Explain why aluminium cannot be extracted by heating its oxide with carbon.
- Aluminium is more reactive than carbon, so carbon cannot remove oxygen from aluminium oxide.
- Electrolysis of the molten oxide (in cryolite) must be used instead.
Section 5 of 7Key terms
Section 6 of 7Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Section 7 of 7Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Ore · Native metal · Reduction · Oxidation · Blast furnace · Electrolysis · Alloy · Cryolite · Slag
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. electronegativity, nucleophile, dynamic equilibrium, activation energy).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
Last updated: