The particle model

Home learning focus

Learn about the particle model.

This lesson includes:

  • one video showing how particles changed when heated
  • two activities


  • 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 will differ.

The particle model

The particle model allows us to visualise how particles are arranged in solids, liquids and gases.

Arrangement of particlesRegular arrangementRandomly arrangedRandomly arranged
Movement of particlesVibrate around a fixed positionMove around each otherMove quickly in all directions
Closeness of particlesVibrate around a fixed positionMove around each otherMove quickly in all directions

Physical properties

It's these arrangement of particles that allows us to understand the different properties of solids, liquids and gases.


Solids tend to be hard and keep a fixed shape. This is because the particles of packed really close together.


Liquids will always fill the shape of the container they are in. This is because the particles move over one another and can move in every direction.


The particles in gases are really far apart from each other and move in all directions. This means they quickly fill the shape of any container they are in and will exert a pressure on the walls of the container.

Changing between states

You can change the state of a substance by increasing or decreasing the amount of heat energy applied to it.

Watch this short clip that demonstrates what happens when you heat up some frozen coconut.

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

As you apply more heat to a solid, the particles gain more energy, causing them to vibrate more and break apart.

This causes the solid to change into a liquid.

The same happen when you heat up a liquid.

The particles gain more energy, so they move further and further apart, becoming a gas.

When we increase the heat on a solid, it begins to melt to become a liquid.
When we increase the heat on a liquid, it will begin to evaporate to become a gas.

When we decrease the heat on a gas, it begins to condense to become a liquid.
When we decrease the heat on a liquid, it will begin to freeze and become a solid.

Did you know?

It’s also possible for a solid to transition directly to a gas! This process is called sublimation.



There are lots of ways to try out your science skills.

Activity 1

Objects around the home

Take an A4 piece of paper and split it into three columns.

Label each one, solid, liquid and gas.

Go around your home and see how many examples of each you can find.

Activity 2

Use this particle model worksheet from Twinkl to check what you have learned.

Particle model

Where next?

Find out more about particle models.

TES: States of matter in science

There's more to learn

Have a look at these other resources around the BBC and the web.

KS3 Chemistry
11-14 Chemistry
Bitesize Daily lessons