iGCSE Chemistry (0620) Core:9.2 Uses of metals: Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
For overhead cables, low density is the key advantage of aluminium—it makes the cables lighter, so they can be strung over longer distances without sagging. Although copper has higher conductivity, aluminium’s lower density is the main reason it is preferred for this specific use. Reactivity doesn’t matter much here because aluminium is protected by its oxide layer. So, only statement 1 explains the choice.
▶️ Answer/Explanation
Detailed solution:
Aluminium is used for overhead power cables precisely because it has a low density (making the cables lighter and easier to support) and because it is a good conductor of electricity. Option A is wrong because aluminium has a low density, not high. Copper is used for wiring because it has excellent ductility, so C is wrong. Copper also has a high density, not low, so D’s description for aircraft manufacture is also incorrect.
▶️ Answer/Explanation
Detailed solution:
Option A is correct: aluminium’s low density (making cables lightweight) combined with its good electrical conductivity make it ideal for overhead power cables where minimising weight is critical. Option B is wrong: aluminium naturally forms a thin, protective oxide layer (Al₂O₃) on its surface that prevents further reaction — this is why aluminium is widely used for food packaging and can last indefinitely. Option C is wrong: copper wiring is insulated with plastic for electrical safety (to prevent electrocution and short circuits), not because copper corrodes easily — copper is actually very resistant to corrosion. Option D is wrong: it is aluminium, not copper, that is used in aircraft manufacture because of its low density; also copper is very malleable.