# Describe what an alloy is and explain why alloys are generally harder than pure metals.

> Cambridge International IGCSE Chemistry (0620) — 9.3 Alloys and their properties · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. An alloy is a mixture of a metal with one or more other elements (metals or non-metals)
2. In a pure metal the atoms are all the same size and arranged in regular layers
3. In an alloy, atoms of different sizes are present / the added element has a different atomic size
4. The different-sized atoms distort / disrupt the regular arrangement so the layers cannot slide over each other as easily, making the alloy harder

## Key terms

- [alloy](https://www.gradenine.co.uk/glossary/alloy)
- [pure metal](https://www.gradenine.co.uk/glossary/pure-metal)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/describe-what-an-alloy-is-and-1fc4ade5) · Published by Druglandscape Ltd.