Uses of Metals
Section: 9. Metals | Syllabus: Cambridge IGCSE Chemistry (0620)
Linking Physical Properties to Uses
Every use of a metal in this topic must be justified by naming the specific physical property/properties that make it suitable. The syllabus names four specific examples, all involving aluminium and copper.
| Metal | Use | Property/properties required |
|---|---|---|
| Aluminium | manufacture of aircraft | low density |
| Aluminium | manufacture of overhead electrical cables | low density and good electrical conductivity |
| Aluminium | food containers | resistance to corrosion |
| Copper | electrical wiring | good electrical conductivity and ductility |
Why "low density" for aircraft and cables? A lighter aircraft uses less fuel; lighter cables put less strain on the pylons that support them.
Why does aluminium resist corrosion? It reacts almost instantly with oxygen in the air to form a thin, tough layer of aluminium oxide that sticks firmly to the surface and stops further reaction underneath - this is covered in more detail in the reactivity series topic.
Why ductility for copper wiring? The metal must be drawable into long, thin wires without breaking.
Worked Example
- Question: give two properties of aluminium that make it suitable for the manufacture of overhead electrical cables. [2]
- Answer: low density (lightweight, so cables put less strain on the pylons) [1]; good electrical conductivity (conducts the current) [1]
Applying the Same Reasoning to Other Objects
An exam question can ask you to apply this property → use reasoning to a metal object that isn't one of the four memorised examples. The skill is always the same: pick out which of the metal's properties are actually relevant to that specific job.
- Question: copper is sometimes used to make cooking utensils. Three properties of copper are listed: 1 corrosion resistant, 2 good conductor of electricity, 3 good conductor of heat. Which properties make copper suitable for making cooking utensils? [1]
- Answer: properties 1 and 3. A cooking pan must transfer heat efficiently from the hob to the food (property 3), and must not corrode when exposed to water, steam and food (property 1). Being a good conductor of electricity (property 2) is irrelevant to a pan on a gas hob, so it is not one of the reasons.
Common Mistakes
- ❌ Naming a true property of the metal that isn't actually relevant to the use being asked about
- ✓ always check the property is actually needed for that specific job - e.g. electrical conductivity is irrelevant to a cooking pan, even though copper does conduct electricity well
- ❌ Giving only one property when a question with 2 marks asks for "two properties"
- ✓ count the marks - both the aircraft/cables use (2 properties for cables) and the copper-wiring use (2 properties) expect two distinct, relevant properties
Interactive revision notes, videos and practice questions load below.