# Iron reacts with sulfur to form iron sulfide. During the reaction, the temperature of the mixture increases. Explain, in terms of bond breaking and bond making, why this reaction is exothermic.

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

## Mark scheme (5 marks)

1. Energy is required / taken in to break bonds
2. Energy is released when new bonds are formed
3. The energy released forming bonds is greater than the energy required to break bonds
4. Therefore there is an overall release of energy to the surroundings
5. This causes the temperature of the mixture / surroundings to increase, showing the reaction is exothermic

## Key terms

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

## 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/iron-reacts-with-sulfur-to-form-249bf386) · Published by Druglandscape Ltd.