# A fixed mass of gas is compressed to a smaller volume at constant temperature. Explain why the pressure of the gas increases.

> Cambridge International IGCSE Physics (0625) — 2.1 Kinetic particle model of matter · Explain · 4 marks

## Mark scheme (4 marks)

1. Gas molecules collide with the walls of the container (to produce pressure)
2. At smaller volume, molecules are closer together / the space is smaller
3. Molecules collide with the walls more frequently
4. More frequent collisions means a greater force per unit area / greater pressure on the walls

## Key terms

- [pressure](https://www.gradenine.co.uk/glossary/pressure)
- [volume](https://www.gradenine.co.uk/glossary/volume)
- [temperature](https://www.gradenine.co.uk/glossary/temperature)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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/a-fixed-mass-of-gas-is-22694a90) · Published by Druglandscape Ltd.