A bottle of perfume is opened in the room why can we smell it after a while

This is called diffusion

Diffusion is when particles move from a high concentration to a low concentration

Diffusion is when particles move from a high concentration to a low concentration

Concentration means how many particles there are High concentration = lots of particles Low concentration = less particles

HIGH concentration of red particles

LOW concentration of

red particles

The RED particles SPREAD out until they are the same

on both sides

We can look at the diffusion of bromine gas from one jar to the other

In this experiment two gases diffuse towards each other

Which particles move faster? Ammonia or acid? The ammonia particles are lighter than the hydrochloric

acid particles, so they diffuse faster

cotton wool soaked in ammonia solution

cotton wool soaked in hydrochloric acid

White ring forms closer

to acid

The white ring is made of ammonium chloride

Diffusion happens quickly in gases, why?

In gases there are lots of spaces between the gas particles The added particles can diffuse (spread out) quickly Gas particles are moving very fast and so the added

particles spread out faster

Diffusion can also happen in liquids This is because the particles in liquids can move around

Diffusion in liquids is slower than diffusion in gases because the particles in a liquid move more slowly

Also there are less spaces between the liquid particles

Diffusion does not happen at all in solids, why?

The particles in a solid can only vibrate on the spot and cannot move around

In order for diffusion to occur the particles must be able to move around

When we add a purple crystal of potassium permanganate to water

We observe diffusion of the purple colour

When we add blue copper sulphate crystals to water, we observe diffusion

We know that matter (solids, liquids and gases) are made up of small particles

If we take a coloured solution and dilute it several times the colour fades away but it does not disappear

This indicates there are lots of small particles in the coloured solution