# A student places a hot drink in a polystyrene cup and notices it stays warm for much longer than when placed in a metal cup. Explain why polystyrene is a better thermal insulator than metal, and describe how adding a lid to the cup improves the situation further.

> Eduqas GCSE Physics — 1.3 Making use of energy · Explain · 4 marks

> Polystyrene cups are often used to keep hot drinks warm. Metal cups allow drinks to cool quickly.

## Mark scheme (4 marks)

1. Metal has a higher thermal conductivity than polystyrene, so energy is transferred by conduction more quickly through metal.
2. Polystyrene acts as thermal insulation, reducing the rate of heat transfer from the drink to the surroundings.
3. Without a lid, energy is also lost from the surface of the drink (by evaporation or convection currents in the air above the liquid).
4. A lid provides thermal insulation at the top, reducing the overall waste energy transfer and slowing the rate of cooling.

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-places-a-hot-drink-5f5cc6a8) · Published by Druglandscape Ltd.