# Explain why evaporation from the surface of a liquid causes the temperature of the remaining liquid to decrease.

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

## Mark scheme (4 marks)

1. Molecules in a liquid have a range / distribution of kinetic energies.
2. Only molecules with the highest kinetic energies (at the surface) have sufficient energy to overcome intermolecular attractive forces and escape.
3. The escaping molecules carry away more than the average kinetic energy, so the average kinetic energy of the remaining molecules decreases.
4. A decrease in the average kinetic energy of the molecules means a decrease in temperature.

## Key terms

- [evaporation](https://www.gradenine.co.uk/glossary/evaporation)
- [temperature](https://www.gradenine.co.uk/glossary/temperature)

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-evaporation-from-the-surface-f5b0b3fc) · Published by Druglandscape Ltd.