# Explain, in terms of molecular motion and collisions, why the pressure of a fixed mass of ideal gas increases when its temperature is raised at constant volume.

> IB DP Physics Standard Level (2023 syllabus) — B.3 Gas laws · Explain · 4 marks

## Mark scheme (4 marks)

1. Raising temperature increases the average kinetic energy (or speed) of the molecules.
2. Faster molecules collide with the walls of the container more frequently.
3. Each collision transfers greater impulse / momentum to the wall because molecules arrive with greater speed.
4. Greater force per unit area on the walls means pressure increases; volume is unchanged so the increase is due entirely to molecular effects.

## Key terms

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

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](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/explain-in-terms-of-molecular-motion-c3fd356b) · Published by Druglandscape Ltd.