# Describe what is observed when excess sodium hydroxide solution is added to aluminium oxide, and explain why this observation shows that aluminium oxide is an amphoteric oxide.

> Cambridge International IGCSE Chemistry (0620) — 7.2 Oxides · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. Aluminium oxide dissolves (in the sodium hydroxide solution)
2. Aluminium oxide reacts with (or is neutralised by) the alkali / sodium hydroxide, showing it behaves as an acid
3. Aluminium oxide also reacts with acids (e.g. hydrochloric acid / sulfuric acid)
4. Because it reacts with both acids and bases/alkalis, it is described as amphoteric

## Key terms

- [amphoteric oxide](https://www.gradenine.co.uk/glossary/amphoteric-oxide)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
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