States of Matter

This lesson covers the three states of matter — solid, liquid and gas — and the changes of state between them, as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the particle model, explain the properties of each state, and describe what happens during state changes in terms of energy and particle arrangement.

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The Three States of Matter

All substances can exist as solids, liquids or gases depending on the temperature and pressure. The particle model helps explain the properties and behaviour of each state.

Particle Arrangements

Property	Solid	Liquid	Gas
Arrangement	Regular pattern (lattice)	Irregular, close together	Random, far apart
Movement	Vibrate about fixed positions	Move around each other	Move rapidly in all directions
Spacing	Very close together	Close together (slightly more spaced than solid)	Very far apart
Energy	Lowest	Medium	Highest
Density	Highest	Medium to high	Very low