# A student is making bread at home. Yeast is added to the dough mixture to help it rise. The student notices that the dough rises much faster when left in a warm kitchen compared to a cold room. Explain why the dough rises faster at higher temperatures, using ideas about particles and activation energy.

> OCR A-Level Chemistry A (H432) — 5.2 Energy · Explain · 5 marks

> Yeast contains enzymes that act as biological catalysts. They break down sugars and release carbon dioxide gas, which causes the dough to rise.

## Mark scheme (5 marks)

1. Higher temperature means particles have more kinetic energy
2. Particles move faster so they collide more often / collision frequency increases
3. A greater proportion of particles have energy equal to or greater than the activation energy
4. This means there are more successful collisions per unit time / rate of reaction increases
5. The enzymes in yeast are biological catalysts that provide a different / alternative reaction pathway with a lower activation energy, increasing the rate of reaction

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](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/a-student-is-making-bread-at-1e5cf909) · Published by Druglandscape Ltd.