Solids, liquids and gases

This lesson covers: 

  1. The three states of matter
  2. Properties of solids, liquids and gases

The three states of matter

Matter exists in three main states - solid, liquid and gas.


The state depends on:

  • Temperature
  • Pressure
  • How strongly the particles are bonded


So heating or cooling a material, or changing the pressure, can cause it to change state.

Properties of solid, liquids and gases

We can tell solids, liquids and gases apart by testing their properties.

Properties of solids

Diagram showing the tightly packed particles in wood and ice, representing the properties of solids.

Solids have tightly packed particles. Examples include: wood, ice, and rocks.


This means that solids have the following properties:

  • A definite volume and shape
  • Very high density
  • Cannot be compressed
  • Do not flow

Properties of liquids

Illustration showing particles of water and honey in containers.

Liquids have particles that can slide past each other. Examples include: water, honey, and oil.


This means that liquids have the following properties:

  • Take the shape of the container
  • Medium density
  • Can’t be compressed
  • Can flow easily

Properties of gases

Illustration comparing the properties of air and helium gases with particles in containers.

Gases have freely moving particles. Examples include: air, helium, and steam (which is the gas form of water).


This means that gases have the following properties:

  • Can fill any container
  • Very low density
  • Easily compressed
  • Can flow and mix with ease