# When iron rusts, it reacts with oxygen and water to form iron oxide. Explain why rusting is a chemical change and not a physical change.

> Eduqas GCSE Chemistry — C4 Chemical changes · Explain · 4 marks

> Iron gates left outside over winter develop a reddish-brown coating of iron oxide (rust). Rusting is a slow process that happens when iron is exposed to both oxygen and water.

## Mark scheme (4 marks)

1. A new substance (iron oxide) is formed
2. The change is irreversible / cannot be easily reversed
3. In a physical change, no new substance is formed / the original substance can be recovered
4. The properties of iron oxide are different from those of iron, showing a chemical reaction has occurred

## Key terms

- [chemical change](https://www.gradenine.co.uk/glossary/chemical-change)
- [physical change](https://www.gradenine.co.uk/glossary/physical-change)
- [iron oxide](https://www.gradenine.co.uk/glossary/iron-oxide)

## Related

- [Revision notes for Eduqas GCSE Chemistry](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/when-iron-rusts-it-reacts-with-853a5add) · Published by Druglandscape Ltd.