# A student leaves an iron nail outside in the rain for several weeks. The nail becomes covered in a reddish-brown solid. The student then places a second iron nail in a bowl of warm water and observes bubbles forming on its surface. Describe the differences between these two processes, stating which is a physical change and which is a chemical change, and giving a reason for each classification.

> Cambridge International IGCSE Chemistry (0620) — 6.1 Physical and chemical changes · Describe · 4 marks

## Mark scheme (4 marks)

1. The formation of reddish-brown solid (rust/iron oxide) on the first nail is a chemical change
2. Because a new substance (iron oxide / rust) is formed / the change is irreversible / difficult to reverse
3. Bubbles forming on the second nail in warm water is a physical change
4. Because no new substance is formed / the change can be reversed / the same substances are still present

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-leaves-an-iron-nail-9acc4fb2) · Published by Druglandscape Ltd.