Uses of Metals

Summary: Metal uses are determined by properties: Al (low density, corrosion-resistant Al2O3 layer) for aircraft and power cables; Cu (excellent conductor, ductile) for wiring and plumbing; Fe/steel (strong, cheap) for construction; Zn (sacrificial protection) for galvanising. Alloys are harder than pure metals because different-sized atoms disrupt the regular layers. Tags: igcse chemistry metals Created: 2026-07-14 Last Updated: 2026-07-16

Aluminium

Key properties:

• Low density (2.70 g/cm3) — about one-third the density of steel
• Corrosion-resistant — develops a thin, tough, impermeable Al2O3 layer that adheres strongly and prevents further attack
• Good conductor of electricity (about 60% as good as copper, but much lighter)
• Good conductor of heat
• Malleable and ductile
• Strong when alloyed (e.g., duralumin: Al + Cu + Mg + Mn)

Major uses linked to properties:

The Al2O3 layer is crucial: when exposed to air, aluminium instantly forms a very thin (about 4 nm) layer of aluminium oxide that is:

• Tough and impermeable — stops further oxygen or water reaching the metal beneath
• Strongly adherent — does not flake off (unlike rust on iron)
• Self-healing — if scratched, fresh Al reacts with O2 to reform the layer

Copper

Key properties:

• Excellent conductor of electricity (second only to silver; silver is too expensive for most uses)
• Excellent conductor of heat
• Malleable and ductile — can be drawn into thin wires without breaking
• Does not react with water at room temperature
• Resistant to corrosion — develops a green patina (copper carbonate/hydroxide) over decades of outdoor exposure which protects the metal beneath

Major uses linked to properties:

Iron and Steel

Pure iron is too soft for most structural uses. Adding carbon (and/or other elements) produces steels with a wide range of properties.

Steels are alloys of iron — the amount of carbon determines the type:

Why stainless steel does not rust: The chromium in stainless steel forms a thin, tough, invisible layer of chromium(III) oxide (Cr2O3) on the surface — similar to the Al2O3 layer on aluminium. This layer is impermeable and self-healing, protecting the iron from rusting.

Why carbon changes the properties of steel: Adding carbon interferes with the regular arrangement of iron atoms, making it harder for layers of iron atoms to slide over each other. More carbon = harder and more brittle.

Zinc

Key properties:

• More reactive than iron (zinc is above iron in the reactivity series)
• Forms a protective oxide/carbonate layer in air
• Resistant to corrosion

Major uses:

Galvanising iron and steel:

• A coating of zinc is applied to iron/steel by dipping in molten zinc (hot-dip galvanising) or by electroplating.
• The zinc layer provides two types of protection:
  1. Barrier protection: the zinc layer prevents oxygen and water from reaching the iron.
  2. Sacrificial protection: even if the zinc coating is scratched, the zinc corrodes preferentially because it is more reactive than iron. As long as zinc remains, iron is protected.
• Why zinc works better than tin: Tin is LESS reactive than iron. If tin-plated steel is scratched, the iron (more reactive) corrodes FASTER at the scratch because it acts as the sacrificial anode to the tin. Zinc, being MORE reactive, corrodes instead of iron.
• Uses: roofing sheets, buckets, dustbins, car underbodies, lamp posts, crash barriers.

Brass (copper-zinc alloy):

• Brass = approximately 70% Cu + 30% Zn (proportions vary).
• Properties: golden colour, harder than pure copper, more corrosion-resistant than pure copper, good acoustic properties.
• Uses: musical instruments (trumpets, trombones), taps and plumbing fittings, door handles, decorative items, electrical plugs and sockets.

Titanium

Key properties:

• Very high strength-to-weight ratio (as strong as steel but ~45% lighter)
• Excellent corrosion resistance — forms a very stable TiO2 layer, resistant to attack by seawater, acids, and chlorine
• High melting point (1668 degrees C)
• Biocompatible — not rejected by the human body

Uses:

Why titanium is expensive: Titanium is extracted by the Kroll process, which involves converting TiO2 to TiCl4, then reducing with molten magnesium under an inert argon atmosphere. The multi-step process, high energy requirements, and need for an inert atmosphere make titanium much more expensive than steel or aluminium.

Why Alloys Are Harder Than Pure Metals

Pure metal structure: In a pure metal, all atoms are the same size. They form regular layers (close-packed planes). When a force is applied, these layers can slide over each other easily — the delocalised electrons move with the ions, so metallic bonding is maintained, but the layers shift position. This makes pure metals soft and malleable.

Alloy structure: An alloy contains atoms of different sizes (e.g., iron atoms with smaller carbon atoms inserted in the gaps, or copper atoms with slightly different-sized zinc atoms substituting for some copper atoms).

• The different-sized atoms disrupt the regular layers.
• When a force is applied, the layers of atoms can no longer slide easily past each other.
• This makes the alloy harder and stronger than the pure metal.

Common alloys:

Key Points

• Aluminium: low density, corrosion-resistant Al2O3 layer → aircraft, power cables, cans, foil
• Copper: excellent conductor, ductile, unreactive with water → electrical wiring, plumbing
• Mild steel (0.05—0.3% C): car bodies, girders, ships
• Hard steel (0.6—1.2% C): cutting tools, chisels, drill bits
• Stainless steel (Fe + Cr + Ni): cutlery, surgical instruments — resistant to rust
• Zinc: galvanising = sacrificial protection (Zn more reactive than Fe, corrodes first)
• Titanium: strong, light, corrosion-resistant → jet engines, artificial joints; expensive (Kroll process)
• Alloys are harder than pure metals because different-sized atoms disrupt the regular layers, preventing easy sliding

Key Concepts from Past Papers

• Alloy: a mixture of a metal with one or more other elements (usually other metals or carbon)
• Galvanising: coating iron/steel with a layer of zinc to protect from rusting
• Sacrificial protection: protection of a metal by attaching a more reactive metal, which corrodes in preference
• Aluminium is used for aircraft bodies because it has a low density/high strength-to-weight ratio
• Aluminium resists corrosion because it forms a protective layer of aluminium oxide
• An alloy is harder because the different-sized atoms disrupt the layers, preventing them from sliding

Keywords from Past Papers

iron, copper, reactive, oxide, carbon, oxygen, chlorine, bromine, magnesium, zinc, metal, earth, line, time, high

Related Notes

• Reactivity of Metals
• Metal Extraction
• Rusting of Iron

Sources

• OpenStax Chemistry 2e — Chapter 12: Kinetics, Rice University (free, CC BY 4.0)
• BBC Bitesize GCSE Chemistry — Uses of Metals, BBC (free educational resource)
• Cambridge IGCSE Chemistry 0620 — Syllabus topic 9 (Metals), Cambridge Assessment International Education
• CK-12 Chemistry for High School — Uses of Metals, CK-12 Foundation (free, CC BY-NC 3.0)

Past Paper Sources

• 0620/31 May/June 2015: Q11(c)(ii) (0m), Q33(a)(i) (0m), Q33(a)(ii) (0m) (+1 more)
• 0620/32 Feb/March 2015: Q44(b)(iv) (2m), Q55(a)(i) (2m), Q55(a)(iii) (2m) (+5 more)
• 0620/32 Feb/March 2017: Q11(a)(iii) (1m)
• 0620/32 Feb/March 2018: Q22(a)(iii) (1m), Q55(a)(iii) (1m), Q55(b)(i) (1m) (+3 more)
• 0620/32 Feb/March 2019: Q33(c)(iii) (4m), Q66(a)(i) (1m), Q66(b)(i) (1m) (+1 more)
• 0620/32 Feb/March 2020: Q22(b)(i) (1m), Q22(d)(i) (1m), Q66(a)(iv) (0m) (+1 more)
• 0620/32 Feb/March 2021: Q55(f)(i) (1m), Q77(e)(iii) (1m)
• 0620/32 Feb/March 2022: Q33(b)(ii) (1m), Q88(d)(iii) (1m)
• 0620/32 Feb/March 2023: Q77(a)(ii) (4m)
• 0620/32 May/June 2018: Q88(e)(iii) (0m)
• 0620/32 May/June 2020: Q11(a)(iv) (1m), Q88(e)(ii) (0m)
• 0620/33 May/June 2016: Q33(b)(ii) (1m), Q44(c)(i) (1m), Q77(d)(i) (1m) (+1 more)

Common Misconceptions