# 2. States of matter

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## The three basic states of matter and their properties

There are 3 basic states of matter:

### Solids

In solids, the forces of attraction between particles are very strong. This means that the particles can only vibrate about a fixed position.

If you heat up the solid, those vibrations increase in amplitude making the particles take up more space. The volume of the solid therefore increases and the material expands slightly.

In a solid, the particles form a regular pattern for many types of materials such as in metals and have a fixed volume and shape.

### Liquids

If you heat up a solid enough, then the solid bonds will break to form weaker liquid bonds.
The particles in a liquid can slide around each other freely creating a random arrangement. However, they are still very close together. This means that it is actually quite difficult to compress a liquid. Try squeezing a full plastic bottle of water to demonstrate this

The shape of a liquid will change to fit its container.

### Gases

Particles in a gas move quickly and randomly in straight lines, until they collide with one another and the container walls.

The distance between particles in a gas is a lot further apart than in a liquid or solid and so the inter-molecular forces between the particles are very weak.

The volume of a gas will change to fill the container it is held in.

N.B. There is another extremely hot state of matter called 'plasma' in which the atoms lose control of their orbiting electrons to form a 'soup' of nuclei and electrons zooming around in random directions. Plasma is found in stars where the temperatures are above 100,000 Celsius!

GCSE Physics Keywords: Solid, Liquid, Gas, Particles

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