# Explain why gases can be compressed much more easily than liquids.

> AQA A-Level Physics (7408) — 3.6.2 Thermal Physics · Explain · 5 marks

> A bicycle pump contains air. When the nozzle is blocked and the handle is pushed in, the air is compressed. A sealed syringe filled with water cannot be compressed in the same way.

## Mark scheme (5 marks)

1. In a gas, the particles are far apart (with large spaces between them)
2. In a liquid, the particles are close together / touching / almost touching
3. Compressing a gas reduces the space / volume between the particles
4. In a liquid there is (almost) no space between particles so they cannot be pushed closer together
5. Therefore a gas can have its volume reduced but a liquid's volume stays (almost) constant when pressure is applied

## Key terms

- [gas](https://www.gradenine.co.uk/glossary/gas)
- [liquid](https://www.gradenine.co.uk/glossary/liquid)
- [compressed](https://www.gradenine.co.uk/glossary/compressed)

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-gases-can-be-compressed-42dbdbd1) · Published by Druglandscape Ltd.