# Explain why a substance in the gaseous state diffuses much more quickly than the same substance in the liquid state.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.1 States of matter · Explain · 4 marks

> Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It occurs in both liquids and gases, but at very different rates.

## Mark scheme (4 marks)

1. Gas particles move randomly / in all directions at high speed (much faster than liquid particles)
2. Gas particles are widely spaced / far apart, so there are fewer collisions / less obstruction between particles
3. Liquid particles are closely packed / close together, so collisions between particles are frequent, slowing diffusion
4. Intermolecular forces in a liquid are stronger than in a gas, restricting the movement of liquid particles

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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-a-substance-in-the-0f841413) · Published by Druglandscape Ltd.