# Explain why the volume of a fixed amount of an ideal gas increases when its temperature is raised at constant pressure.

> IB DP Chemistry Standard Level (2023 syllabus) — S1.5 Ideal gases · Explain · 4 marks

## Mark scheme (4 marks)

1. Raising temperature increases the average kinetic energy (or speed) of the gas particles.
2. Faster-moving particles collide with the container walls more frequently and/or with greater force, tending to increase pressure.
3. Because pressure is held constant, the volume must increase to restore (keep) the same rate/force of collisions per unit area.
4. This is consistent with Charles's law: volume is directly proportional to absolute (kelvin) temperature at constant pressure.

## Key terms

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

## Related

- [Revision notes for IB DP Chemistry 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-why-the-volume-of-a-93c4b10b) · Published by Druglandscape Ltd.