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States of Matter

Exam code: 5054
Written by: Ashika|Reviewed by: Caroline Carroll|Updated 2 July 2026

Properties of Solids, Liquids & Gases

Properties of Solids, Liquids & Gases

  • The three states of matter are solids, liquids and gases

A solid, a liquid and a gas

Shape and volume, IGCSE & GCSE Physics revision notes

The three states of matter in terms of shape and volume

Solids

  • Solids have a definite shape and a definite volume

    • Solids cannot flow and are incompressible

Liquids

  • Liquids have no definite shape but do have a definite volume

    • Liquids are able to flow to take the shape of a container but they are incompressible

Gases

  • Gases have no definite shape and no fixed volume

    • Gases can flow to take the shape of their container and are highly compressible

Changes of State

Changes of State

When a substance changes state, the number of molecules in that substance doesn't change and so neither does its mass

  • The only thing that changes is its energy

  • Changes of state are physical changes and so they are reversible

Melting & Freezing

  • Melting occurs when a solid turns into a liquid (e.g. ice to water)

  • Freezing occurs when a liquid turns into a solid

Boiling & Condensing

  • Boiling occurs when a liquid turns into a gas

    • This is also called evaporating

  • Condensing occurs when a gas turns into a liquid

Diagram of Changes of State

2-1-1-states-of-matter-changes-of-state-cie-igcse-23-rn

Melting and freezing are changes between solid and liquid states, boiling and condensing are changes between liquid and gas states