High School Physics

# The kinetic theory of matter

The idea that all substances contain incredibly small moving particles is called the kinetic theory of matter. The word ‘kinetic’ comes from a Greek word meaning moving.

[Related Post: Kinetic Theory of gases]

## The main points of the kinetic theory of matter

The main points of the kinetic theory of matter are:

• All matter is made up of tiny, invisible, moving particles. These particles are atoms, molecules, and ions.
• Particles of different substances have different sizes. Particles of elements, like iron, copper, and sulfur, are very small. Particles of compounds, like petrol and sugar, are larger, but still very small.
• Small particles move faster than larger particles at the same temperature.
• As the temperature rises, the particles have more energy and move around faster.
• In a solid, the particles are very close and arranged in a regular pattern. They can only vibrate about fixed positions.
• In a liquid, the particles are not in a regular arrangement. They have more energy and they can slide past each other.
• In a gas, the particles are far apart. They move very fast and randomly in all the space they can find.

Related Post: Kinetic Theory of gases

### Use of kinetic theory of matter

The kinetic theory of matter can be used to explain how a substance changes from one state to another. These changes are usually caused by heating or cooling.