# Explain why silicon dioxide has a high melting point and does not conduct electricity.

> Edexcel GCSE Chemistry (1CH0) — 1.7 Types of substance · Explain · 4 marks

> Silicon dioxide is used to line the inside of furnaces because it can withstand very high temperatures. It is also used as an electrical insulator in some electronic components.

## Mark scheme (4 marks)

1. Silicon dioxide has a giant covalent (macromolecular) structure
2. There are many strong covalent bonds throughout the structure
3. A large amount of energy is needed to break these bonds, so the melting point is high
4. There are no free/delocalised electrons (and no ions free to move), so it cannot conduct electricity

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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/explain-why-silicon-dioxide-has-a-f1c7b833) · Published by Druglandscape Ltd.