# A student adds a spatula of ammonium nitrate crystals to a test tube containing a small volume of water and stirs the mixture. The outside of the test tube feels noticeably cold to the touch. Describe what this observation tells us about the energy change occurring, and explain, in terms of bonds, why the temperature of the surroundings decreases.

> Cambridge International IGCSE Chemistry (0620) — 5.1 Exothermic and endothermic reactions · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. The reaction is endothermic
2. Energy is transferred from the surroundings to the reaction / reactants
3. Energy is required to break bonds (in the reactants)
4. The energy needed to break bonds is greater than the energy released when new bonds form, so there is an overall net absorption of energy

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-adds-a-spatula-of-eddf719d) · Published by Druglandscape Ltd.