2.5.3Atoms, Elements and Compounds
Using Metals — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 4 parts Lesson 12 of 26 Unit quiz
Section 1 of 4Aluminium
Aluminium is light, a good conductor and resists corrosion, which makes it useful in transport, cooking and power lines.
Aircraft bodies
- A high strength-to-weight ratio, because aluminium has a low density, keeps aircraft light but strong.
Saucepans
- Aluminium conducts heat very well and is unreactive, so it heats food evenly without being affected by it.
Overhead cables
- Aluminium is a very good conductor of electricity and it is light enough to be supported on pylons.
Food cans
- It is non-toxic and resists corrosion and attack by acidic foods, so the contents stay safe.
Section 2 of 4Copper and Steel
Copper is chosen for its conductivity and ductility, and steel for its strength and hardness.
Copper and Steel
Electrical wiring
- Copper conducts electricity very well and is ductile, so it can be drawn into long thin wires.
Water pipes
- Copper does not react with water, is non-toxic and is malleable, so it can be bent into shape.
Mild steel
- Steel with about 0.25% carbon is soft and malleable, which suits car body panels and wiring.
Stainless steel
- Steel alloyed with chromium and nickel is strong and resists corrosion, so it suits cutlery and sinks.
| Metal | Use | Key property |
|---|---|---|
| Aluminium | Aircraft bodies | High strength-to-weight ratio |
| Aluminium | Overhead cables | Very good conductor of electricity |
| Copper | Saucepans | Very good conductor of heat and unreactive |
| Iron (steel) | Building material | Good strength, malleable and relatively inexpensive |
Section 3 of 4Matching Property to Use
Engineers and manufacturers choose a metal by comparing its properties with the job it must do.
1
First identify what the object must do, such as carry current, resist corrosion or bear a heavy load.
2
Then choose the metal whose property matches that requirement, such as copper for electrical wiring.
3
Consider cost and mass as well, because a light, cheap metal may be preferred even if another is stronger.
4
Finally check that the chosen metal is safe for its purpose, such as non-toxic aluminium for food cans.
Section 4 of 4Exam Checklist & Tips
2.5.3 – Key Points for the Exam
- Ductile Able to be drawn into a wire without breaking.
- Malleable Able to be hammered or rolled into shape without breaking.
- Strength-to-weight ratio
- How strong a material is compared with its mass;
- high values suit aircraft.
- How strong a material is compared with its mass;
- Corrosion resistance The ability of a metal to resist being attacked by air, water or other substances.
- Conductor A material that allows electricity or heat to pass through it easily.
Common Mistakes
- Giving a use without linking it to a property; the answer must say why the property matters for that use.
- Saying aluminium resists corrosion because it is unreactive;
- it is protected by a thin, tough layer of aluminium oxide.
- Confusing ductile (drawn into wires) with malleable (hammered into sheets).
- Stating that steel is a pure metal; steel is an alloy of iron with carbon.
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