# A student mixes sodium hydroxide solution with hydrochloric acid in a polystyrene cup. The temperature of the mixture rises. Explain why the temperature rises and why a polystyrene cup is used instead of a glass beaker.

> AQA A-Level Chemistry (7405) — 3.1.4 Energetics · Explain · 5 marks

> Exothermic reactions release energy to the surroundings, causing a temperature rise. Polystyrene is a thermal insulator.

## Mark scheme (5 marks)

1. The reaction is exothermic
2. Energy is transferred from the reaction/chemicals to the surroundings/solution
3. The bonds formed in the products release more energy than is required to break bonds in the reactants
4. Polystyrene is a good thermal insulator / reduces energy transfer to the surroundings
5. This gives a more accurate/reliable temperature change measurement

## 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-mixes-sodium-hydroxide-solution-72eb9fea) · Published by Druglandscape Ltd.