Diffusion occurs in everyday life. For example, whenever someone sprays perfume you will eventually smell it across the room. This is an instance of diffusion.

Diffusion is correctly defined as the movement of particles from a region of high concentration (many particles in a small area) to a region of low concentration (few particles in a small area). When the particles are released in the surroundings, they randomly move until there is an even distribution of the particles throughout.


Diffusion is mostly seen in liquids and with gases. This is because solid particles are held together very closely and cannot move very far. When molecules can move freely, they tend to spread themselves out as evenly as possible.

Diffusion not only occurs in everyday life within the environment, it also occurs within the bodies of living organisms.


-The oxygen and nutrients from a mother is transported across the placenta via diffusion to the foetus during pregnancy.

-Carbon dioxide needed for photosynthesis is diffused from the atmosphere into plants through pores called the stomata.

Many other instances of diffusion occur in both plants and animals.  The rate at which diffusion occurs depends on the concentration gradient. The concentration gradient is the gradual difference in concentration between two regions. The greater the difference in the concentration, the steeper the concentration gradient and the faster diffusion will occur faster.

Space 1                       Space 2

000                             00000000

Space 3                       Space 4

00                               0000

Diffusion will occur faster from space 2 to space 1 than from space 4 to space 3.


Fill a container with water and leave it to stand. Place some dye in the container of water, as shown above and leave for about 10 minutes. What do you think will be seen after the time has passed?

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