# Explain why silicon dioxide has a much higher melting point than carbon dioxide, even though both substances contain covalent bonds.

> Edexcel GCSE Chemistry (1CH0) — 1.6 Covalent bonding · Explain · 4 marks

> Silicon dioxide is used to line furnaces because it can withstand very high temperatures. Its melting point is above 1600 °C. Carbon dioxide, which also contains covalent bonds, is a gas at room temperature.

## Mark scheme (4 marks)

1. Carbon dioxide is a simple molecular substance
2. Carbon dioxide has weak intermolecular forces between its molecules
3. Silicon dioxide has a giant covalent structure
4. Many strong covalent bonds must be broken to melt silicon dioxide, requiring much more energy

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](https://www.gradenine.co.uk/learn)
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