# Barium oxide is an ionic compound. When barium oxide is dissolved in water, the resulting solution conducts electricity. Explain why solid barium oxide does not conduct electricity, but the aqueous solution does.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.6 Ionic compounds · Explain · 4 marks

## Mark scheme (4 marks)

1. In solid barium oxide, the ions are held in fixed positions (in a giant lattice) and cannot move freely
2. Because ions cannot move in the solid, charge cannot be carried / no electrical current can flow
3. When dissolved in water, the ions separate / dissociate and are free to move throughout the solution
4. The free-moving ions carry charge through the solution, allowing electrical conduction

## Key terms

- [ionic compound](https://www.gradenine.co.uk/glossary/ionic-compound)
- [ion](https://www.gradenine.co.uk/glossary/ion)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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/barium-oxide-is-an-ionic-compound-1d993694) · Published by Druglandscape Ltd.