# Explain why two objects made of different materials but with the same mass, initially at the same high temperature, cool down to room temperature at different rates when placed in identical surroundings.

> IB DP Physics Higher Level (2023 syllabus) — B.1 Thermal energy transfers · Explain · 4 marks

> Two metal blocks, one made of aluminium and one made of lead, each with a mass of 500 g and initially at 200 °C, are placed on a thermally insulating surface in a room at 20 °C.

## Mark scheme (4 marks)

1. Both blocks lose thermal energy to the surroundings at a rate that depends on their temperature difference with the surroundings and on surface properties, which are identical here.
2. The temperature change of each block depends on its specific heat capacity; a material with a larger specific heat capacity requires more thermal energy to change its temperature by 1 K per unit mass.
3. Aluminium has a much greater specific heat capacity than lead, so for the same rate of energy loss, aluminium's temperature decreases more slowly.
4. Therefore the lead block reaches room temperature faster / the aluminium block takes longer to cool because its temperature decreases by a smaller amount for each unit of energy transferred away.

## Related

- [Revision notes for IB DP Physics Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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