# Evaporation from the surface of a liquid causes the liquid to cool. Explain why the liquid cools as evaporation takes place.

> Pearson Edexcel International GCSE Physics (4PH1) — 5.2 Change of state · Explain · 4 marks

> Nurses sometimes wipe a patient's skin with a liquid alcohol solution before giving an injection. The patient feels a cooling sensation on their skin as the alcohol evaporates.

## Mark scheme (4 marks)

1. Only molecules with the highest kinetic energy escape from the surface during evaporation
2. The remaining molecules have a lower average kinetic energy
3. Temperature is a measure of the average kinetic energy of the particles, so a lower average kinetic energy means a lower temperature
4. Evaporation occurs at the surface of the liquid and can happen at any temperature (not just the boiling point)

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](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/evaporation-from-the-surface-of-a-8aca60a6) · Published by Druglandscape Ltd.