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Home » Science Experiments for Kids » Diffusion Demonstration

Diffusion Demonstration

Modified: Mar 27, 2025 · Published: Mar 29, 2021 by Emma Vanstone · This post may contain affiliate links · 1 Comment

Imagine pulling a delicious cake out of an oven. The smell slowly spreads around the room and then through the house. This is diffusion! The lovely cake smelling particles move from where there are lots of them ( high concentration ) to where there are less of them ( low concentration ). Diffusion can be quite a slow process as the movement of particles is random. One very easy diffusion demonstration is to pour squash or food colouring into a glass of water and watch as the colour spreads through the glass.

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration until its concentration becomes equal throughout the available space.

This video shows diffusion in action.

Diffusion Demonstration with Squash and Water

Food colouring or juice in water is a great demonstration of diffusion. You can see the food colouring starts in one area and then starts to spread from areas of high food colouring concentration to areas of low food colouring concentration. Eventually, the food colouring spreads throughout the whole glass and the colour becomes paler and even throughout. ​

I used food colouring in the images below to make the process easier to see.

Diffusion using food colouring and water

Food colouring in water, used to demonstrate diffusion
yellow squash in water for a diffusion demonstration

​

Blue food colouring spreading through water for a diffusion demonstration

What is diffusion?

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

Diffusion occurs in gases and liquids. Particles in gases and liquids move around randomly, often colliding with each other or whatever container they are in. When they collide, they change direction, which means eventually they spread out through the whole available space.

Examples of Diffusion

Diffusion in humans

Oxygen diffuses from the alveoli of the lungs into red blood cells. This is because the concentration of oxygen in the alveoli is high, and the concentration of oxygen in the red blood cells is low. Red blood cells have very thin cell walls, which allow oxygen to diffuse easily in and out of them.

Diffusion in plants

Plants use carbon dioxide from the air for photosynthesis. Carbon dioxide enters the leaves through small holes called stomata on the underside of the leaf. Spongy cells called mesophyll cells allow gases to diffuse easily in and out of the leaf. The stomata can open and close so the plant doesn’t lose too much water.

diagram of a leaf

More diffusion demonstrations

Making a cup of tea is another great diffusion demonstration. This diffusion activity using different shaped tea bags is great fun.

Spray perfume in a room. The smell will slowly spread through the available space.

Another example of the movement of substances important for living things is osmosis.

Image of food colouring spreading out in water for a diffusion demonstration

Last Updated on March 27, 2025 by Emma Vanstone

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Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

Comments

  1. Nafisah

    December 31, 2024 at 6:42 pm

    This website is superb. It has shown me experiments of diffusion within my own environment which has made me understand it more better and simpler. Thank you

    Reply

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