# Explain why a liquid evaporates at temperatures well below its boiling point, and why the rate of evaporation increases when the surface area of the liquid is increased.

> IB DP Chemistry Higher Level (2023 syllabus) — S1.1 Introduction to the particulate nature of matter · Explain · 4 marks

## Mark scheme (4 marks)

1. Particles in a liquid have a distribution (range) of kinetic energies at any given temperature.
2. Some particles at the surface have sufficient kinetic energy to overcome intermolecular forces and escape into the gas phase, even below the boiling point.
3. Increasing surface area exposes more particles at the surface, so more particles per unit time are able to escape.
4. Therefore the rate of evaporation increases because more high-energy particles can leave the liquid per unit time.

## Key terms

- [evaporation](https://www.gradenine.co.uk/glossary/evaporation)
- [surface area](https://www.gradenine.co.uk/glossary/surface-area)
- [rate of evaporation](https://www.gradenine.co.uk/glossary/rate-of-evaporation)

## Related

- [Revision notes for IB DP Chemistry 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-a-liquid-evaporates-at-c79e78fc) · Published by Druglandscape Ltd.