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

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

## Mark scheme (4 marks)

1. Molecules in a liquid have a distribution of kinetic energies / speeds (Maxwell–Boltzmann distribution).
2. Only the most energetic / fastest-moving molecules near 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 mean kinetic energy of the remaining molecules decreases.
4. Since temperature is proportional to the mean kinetic energy of the molecules, the temperature of the remaining liquid falls.

## 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 Higher 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-099916e1) · Published by Druglandscape Ltd.