# Explain why the internal energy of a liquid increases as it evaporates, and describe what happens to the arrangement and movement of its particles during this change of state.

> Edexcel GCSE Physics (1PH0) — 14.1 Particle model · Explain · 4 marks

> A puddle of water left in the sun slowly disappears over several hours as the water evaporates.

## Mark scheme (4 marks)

1. The internal energy increases because energy is absorbed (from the surroundings/sun) during evaporation
2. The potential energy of the particles increases (as intermolecular forces are overcome / particles move further apart)
3. The particles spread far apart / become widely spaced (from being in contact in the liquid state to being spread apart in the gas state)
4. Particles move randomly in all directions with high kinetic energies (rather than flowing over each other as in a liquid)

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](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-the-internal-energy-of-0f6c5f61) · Published by Druglandscape Ltd.