What are solids, liquids and gases?

  • Everything is made up of tiny particles.

  • The properties of a substance depend on what its particles are like, how they move and how they are arranged.

  • The particles in a substance are the same whether it's in the solid, liquid or gas state, but their arrangement and movement change.

Lard melting in a frying pan
A case study video on how a chef applies the concept of solid, liquid and gas to their job.

How do solids, liquids and gases differ?

Everything is made up of tiny particles. The properties of a substance depend on what its particles are like, how they move, and how they are arranged.

Most substances can exist in three states: solid, liquid and gas. The particles of a substance are the same in each state, but their arrangement and movement change. This explains the different behaviour of a substance in its three states.

Solids

In the solid state the vibrating particles form a regular pattern. This explains the fixed shape of a solid and why it can’t be compressed or poured.

Liquids

In a liquid the particles still touch their neighbours but they move around, sliding over each other. This is why you can pour, but not compress, a liquid.

Gases

In the gas state, widely-spaced particles move around randomly. This explains why you can compress gases and why they flow.

Models of atomic structure for solid, liquid and gas.