# State and explain two reasons why steel (an alloy of iron) is used to make bridges rather than pure iron.

> Cambridge International IGCSE Chemistry (0620) — 9.2 Uses of metals · State and explain · 4 marks

## Mark scheme (4 marks)

1. Steel is stronger / harder than pure iron
2. Explanation: carbon atoms (or other atoms) disrupt the regular layers of iron atoms, preventing them from sliding over each other
3. Steel is more resistant to corrosion / rusting than pure iron
4. Explanation: the presence of other elements (e.g. chromium in stainless steel) prevents oxygen and water from reacting with the iron / reduces oxidation

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "State and explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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