# Explain, using the kinetic model of an ideal gas, why the pressure of a fixed mass of gas increases when its temperature is raised at constant volume.

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

## Mark scheme (4 marks)

1. Raising the temperature increases the average kinetic energy (or average speed) of the gas molecules.
2. Molecules collide with the container walls more frequently (because they travel between walls in less time).
3. Each collision transfers greater impulse (or force) to the wall because the molecules arrive with greater momentum.
4. The total force per unit area (pressure) on the walls therefore increases; since volume is constant, no competing effect reduces the pressure.

## Key terms

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

## Related

- [Revision notes for IB DP Physics Higher 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-using-the-kinetic-model-of-053eb865) · Published by Druglandscape Ltd.