# Explain why increasing the concentration of a reactant increases the rate of a chemical reaction.

> Eduqas GCSE Chemistry — C6 Rate and extent of chemical change · Explain · 4 marks

> A student is investigating how the concentration of hydrochloric acid affects how quickly it reacts with marble chips.

## Mark scheme (4 marks)

1. Higher concentration means more particles (of reactant) in the same volume
2. Particles collide more frequently / there are more collisions per unit time
3. More collisions have sufficient / enough energy to overcome the activation energy
4. Therefore the rate of reaction increases

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-increasing-the-concentration-of-630d6fbb) · Published by Druglandscape Ltd.