# A sealed metal canister contains a fixed mass of gas. The canister is placed in a freezer and left until the temperature of the gas has fallen significantly. The volume of the canister does not change. Explain why the pressure of the gas inside the canister decreases.

> AQA GCSE Physics (8463) — 4.3.3 Particle model and pressure (Phys only) · Explain · 4 marks

## Mark scheme (4 marks)

1. The temperature of the gas falls, so the average kinetic energy of the molecules decreases
2. The molecules move more slowly / have lower average speed
3. The molecules collide with the walls of the container less frequently
4. Each collision exerts a smaller force on the wall, so the total force per unit area (pressure) is lower

## Key terms

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

## Related

- [Revision notes for AQA GCSE Physics (8463)](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-sealed-metal-canister-contains-a-304c7e02) · Published by Druglandscape Ltd.