# Silicon dioxide is a giant covalent structure used to make glass and heat-resistant laboratory equipment. Explain why silicon dioxide has a high melting point and does not conduct electricity.

> OCR GCSE Chemistry A: Gateway Science (J248) — C2.3 Properties of materials · Explain · 4 marks

> Silicon dioxide is found naturally as quartz and is used in applications that require resistance to very high temperatures. Unlike metals, it does not conduct electricity in any state.

## Mark scheme (4 marks)

1. Silicon dioxide contains many atoms held together by strong covalent bonds
2. A large amount of energy is needed to break these strong covalent bonds, so the melting point is high
3. There are no free/delocalised electrons in silicon dioxide
4. Charge cannot be carried through the structure, so it does not conduct electricity

## Key terms

- [giant covalent structure](https://www.gradenine.co.uk/glossary/giant-covalent-structure)
- [melting point](https://www.gradenine.co.uk/glossary/melting-point)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/silicon-dioxide-is-a-giant-covalent-e0d538e9) · Published by Druglandscape Ltd.