• Understand that the particle model can be used to explain the different states of matter

There are three states of matter that you need to be concerned with in GCSE, these are solids, liquids and gases.

The particle model is a model used to help explain and understand the particle arrangement of the three states.

Why is it that solids are harder to break, pierce or change shape than liquids? Why are gases so hard to contain?

You should be familiar with the three states of matter as these were studied in year 7. They take the following form;

Image result for solids liquids and gases

Each state can be compared to one another by focussing on the particle arrangement, movement and distance from one another;


  • Particles are in the form of a pattern, they have a regular arrangement
  • They vibrate about their fixed positions
  • The are close together


  • Particles are not in a pattern, they have an irregular arrangement
  • They move around one another
  • They move quickly in all directions


  • Particles are randomly arranged
  • They move quickly in all directions
  • The average distance between particles is ‘far apart’.


Question:  Explain why the particles in a solid cannot move around freely.

The particles in a solid are in a fixed, regular arrangement and so can only vibrate about a fixed position. They are held together by strong forces of attraction.

You should get into the habit of linking areas of Physics together. In this case we can link the forces of attraction between particles and the energy that the particles have with the different states;

Changing State

The image above shows the different states of matter and the change of state required for the state to change. In any case show the difference ultimately is down to the difference in energy between the state of matter and the surrounding environment that that matter is in. In other words, if you took an ice cube, it currently has little energy which is why it is in a solid state. If you supply the ice cube with thermal energy using your body heat, you will transfer some of your energy to it and cause it to melt into a liquid. If you then secure that liquid above a Bunsen burner it will supply enough energy to break bonds further and to cause the liquid to turn to a gas.

The opposite thing happens if energy is lost from the state. The energy escapes, the state cools down and the particles move less. When they move less they get closer together and strong bonds between them form.

There is a fourth state of matter that you may have seen in images or read about, can you name it and explain what it is?

Click here for the answer

Further reading: