# Explain, using particle theory, why a solid substance keeps a fixed shape but a liquid takes the shape of its container.

> Edexcel GCSE Chemistry (1CH0) — 2.1 States of matter · Explain · 4 marks

## Mark scheme (4 marks)

1. In a solid, particles are held in a regular arrangement
2. Solid particles can only vibrate about fixed positions, so the overall shape cannot change
3. In a liquid, particles are arranged randomly and close together
4. Liquid particles are able to move past each other, so the liquid can flow and fill the shape of the container

## Key terms

- [particle theory](https://www.gradenine.co.uk/glossary/particle-theory)
- [solid](https://www.gradenine.co.uk/glossary/solid)
- [liquid](https://www.gradenine.co.uk/glossary/liquid)

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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-using-particle-theory-why-a-03b5391c) · Published by Druglandscape Ltd.