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

> AQA GCSE Chemistry (8462) — 4.2.2 How bonding and structure are related to the properties of substances · Explain · 4 marks

> Silicon dioxide is used to line furnaces because it can withstand very high temperatures. It is a giant covalent structure.

## Mark scheme (4 marks)

1. Silicon dioxide has many strong covalent bonds
2. A large amount of energy is needed to break these bonds / overcome these bonds
3. There are no free/delocalised electrons (in silicon dioxide)
4. So there are no charged particles free to move / carry charge

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