# A fixed quantity of gas is compressed to a smaller volume at constant temperature. Explain, in terms of particles, why the pressure of the gas increases.

> Eduqas GCSE Physics — 2.6 Particle physics and using physics to investigate the universe · Explain · 4 marks

## Mark scheme (4 marks)

1. The particles collide with the walls of the container, producing a (perpendicular) force on the walls / surfaces
2. Pressure is the (perpendicular) force per unit area on the container walls
3. At smaller volume the particles are closer together / the same number of particles occupy a smaller space, so collisions with the walls are more frequent
4. More frequent collisions mean a greater (perpendicular) force per unit area on the walls, so pressure is higher

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Physics](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-quantity-of-gas-is-06702052) · Published by Druglandscape Ltd.