Kinetic particle theory

The kinetic particle theory explains the properties of the different states of matter. The particles in solids, liquids and gases have different amounts of energy. They are arranged differently and move in different ways.

The table summarises the arrangement and movement of the particles in solids, liquids and gases, and shows simple diagrams for the arrangement of these particles.

Particle arrangement and movement

Solid: Close together, regular pattern, vibrate on the spot. Liquid: Close together, random arrangement, move around each other. Gas: Far apart, random arrangement, move quickly in all directions.

Solids

Properties Why they are like this
They have a fixed shape and cannot flow The particles cannot move from place to place
They cannot be compressed or squashed The particles are close together and have no space to move into

Liquids

Properties Why they are like this
They flow and take the shape of their container The particles are free to move around each other
They cannot be compressed or squashed The particles are close together and have no space to move into

Gases

Properties Why they are like this
They flow and completely fill their container The particles can move quickly in all directions
They can be compressed or squashed The particles are far apart and have space to move into
Glossary
  1. botanist A scientist who studies plants.
  2. condensation A change of state in which gas becomes liquid by cooling.
  3. heat energy Heat energy is the product of the movement of particles such as, atoms, ions and molecules. It is also known as thermal energy.
  4. kinetic energy Energy which an object possesses by being in motion.
  5. mass The amount of matter an object contains. Mass is measured in grams (g).
  6. particle theory The scientific theory used to explain the properties of solids, liquids and gases. It involves the arrangement and movement of the particles in a substance.
  7. volume The volume of a three-dimensional shape is a measure of the amount of space or capacity it occupies, eg a can of cola has a volume of 330 ml.