# Describe what happens to the particles in a fixed mass of gas when the gas is heated at constant volume, and explain how this causes the pressure of the gas to increase.

> Eduqas A-Level Physics — 3.4 Thermal physics · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Heating the gas increases the temperature of the gas / gives the particles more energy
2. The particles move faster / have greater average speed
3. Particles collide with the walls of the container more frequently
4. Each collision with the wall exerts a greater force on the wall / particles hit the walls harder
5. More frequent and/or harder collisions result in greater force per unit area on the walls, so pressure increases

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/describe-what-happens-to-the-particles-a0bafd9d) · Published by Druglandscape Ltd.