# A student dissolves ammonium nitrate in water. The temperature of the solution decreases. Explain why the temperature decreases, in terms of energy changes in bond breaking and bond forming.

> AQA A-Level Chemistry (7405) — 3.1.8 Thermodynamics (A-Level only) · Explain · 5 marks

> When ammonium nitrate dissolves in water, the solution becomes noticeably colder.

## Mark scheme (5 marks)

1. Energy is needed / absorbed to break bonds (between ions in the lattice / between ammonium nitrate particles)
2. Energy is released when new bonds form (between ions and water molecules / during hydration)
3. More energy is absorbed (breaking bonds) than is released (forming bonds)
4. The overall process is endothermic
5. The solution / surroundings loses energy / heat energy is transferred from the surroundings to the reaction, so temperature of the solution decreases

## Key terms

- [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 A-Level Chemistry (7405)](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-dissolves-ammonium-nitrate-in-04033396) · Published by Druglandscape Ltd.