# Explain why, at very high temperatures and low pressures, the behaviour of a real gas approaches that of an ideal gas.

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

## Mark scheme (4 marks)

1. At high temperatures, molecules have much greater (average) kinetic energy
2. Intermolecular forces become negligible compared to the kinetic energy of the molecules, so molecules behave as if no attractions exist between them
3. At low pressures, molecules are far apart / the volume of the molecules themselves is negligible compared to the total volume of the container
4. Both assumptions of the ideal gas model (negligible molecular volume and no intermolecular forces) are therefore satisfied, so the real gas obeys pV = nRT

## Key terms

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

## Related

- [Revision notes for IB DP Chemistry 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)

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