Cambridge IGCSE Chemistry · Syllabus 0620 · Metals
Density
What is Density?
The mass of a material per unit volume. A low-density material gives a large object for a small mass, which is why aluminium rather than a denser metal is chosen for aircraft bodies and for overhead cables that must not sag under their own weight.
This definition is part of the Metals chapter in Cambridge IGCSE Chemistry.
Common mistakes with Density
- 9. “Overhead cables should be copper, because copper is the better conductor.” Core 9.2.1 Defect Optimises the wrong property for the situation. Reason The cable also has to hold itself up over a long span. Aluminium’s low density is what makes that possible. Repair “Aluminium is used, because it has a low density and is a good conductor.” Transfer Why is copper right for house wiring? A short wire inside a wall does not have to support itself, so the better conductivity wins.
Examiner tips on Density
- Two-part structure. “Aluminium is used for aircraft because it has a low density” is half the answer. Adding “so the aircraft has a smaller mass and uses less fuel” is the other half. The property alone is never the whole answer.