# Explain why a gas exerts a pressure on the walls of its container, and why this pressure increases when the gas is heated at constant volume.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.1 States of matter · Explain · 4 marks

## Mark scheme (4 marks)

1. Gas particles move randomly (in all directions) and collide with the walls of the container
2. These collisions (with the walls) exert / create a force on the walls, which produces pressure
3. When heated, particles gain (kinetic) energy and move faster
4. Faster-moving particles collide with the walls more frequently and/or with greater force, so pressure increases

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-a-gas-exerts-a-fce4800a) · Published by Druglandscape Ltd.