In this module, you will learn:

  • the process of diffusion
  • the speed of diffusion between solids, liquids and gases

Resources to help you:

  • Textbook: page 54, 55 and 56
  • Notebook: page 27 (4)

Watch the video

See how the particles move during diffusion of sugar cube in water.


You can change the speed to 0.75x to make it easier to listen.

Before we begin to learn about diffusion, it is useful to recap what we learnt last week about the Kinetic Particle Theory.

The Kinetic Particle Theory


This theory is useful to help us understand about the atoms or molecules inside the three states of matter. It helps us to better understand the properties of solids, liquids and gases.

So there are a few things to consider:

  1. All matter are made of tiny particles (atoms or molecules or ions)
  2. All particles are constantly moving
  3. The speed of the movement depends on the amount of energy the particles have




What is diffusion?


Diffusion is the random movement of particles from an area of higher concentration to an area of lower concentration.

One way to visualise the meaning of concentration is the amount of particles in a particular area.

If there is a lot of particles, then it is of a higher concentration.

If there is very small amount of particles, then it is of lower concentration.


Watch the video

Watch the diffusion of bromine gas (a coloured gas) in action

Useful to answer Question 2, page 55 of your Homework


You can change the speed to 0.75x to make it easier to listen.

Particles in liquids

Particles in solids

Particles in gases

Speed of diffusion


The speed of diffusion depends on a few factors:

  1. Diffusion in gases happens faster than in liquids, and
  2. Diffusion in liquids are faster than in solids.
  3. Diffusion happens faster if the temperature is higher (hotter) and slower if the temperature is lower (colder)

This can be easily explained using the kinetic particle theory.

  1. Gas particles have higher energy than liquid particles.
  2. Liquid particles have higher energy than solid particles.
  3. Particles at a higher temperature (hotter) has more energy.

So the more energy the particles have, the faster they move and as a result, diffusion becomes faster.

Ready for the next module?

In the next module, we will look at elements.

Scroll to Top