# A student mixes citric acid and sodium hydrogencarbonate in a beaker. The temperature of the mixture decreases. Explain why the temperature decreases, in terms of energy transfer to or from the surroundings and bond breaking and bond forming.

> AQA GCSE Chemistry (8462) — 4.5.1 Exothermic and endothermic reactions · Explain · 4 marks

## Mark scheme (4 marks)

1. The reaction is endothermic
2. Energy is taken in from the surroundings (causing the temperature to decrease)
3. Energy is required / supplied to break bonds in the reactants
4. The energy needed to break bonds is greater than the energy released when new bonds are formed (in the products)

## Key terms

- [surroundings](https://www.gradenine.co.uk/glossary/surroundings)
- [bond breaking](https://www.gradenine.co.uk/glossary/bond-breaking)
- [bond forming](https://www.gradenine.co.uk/glossary/bond-forming)

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](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-mixes-citric-acid-and-29a0d597) · Published by Druglandscape Ltd.