Diffusion & Dilution (Edexcel IGCSE Chemistry (Modular))

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Diffusion and dilution

  • Diffusion and dilution experiments support a theory that all matter (solids, liquids and gases) is made up of tiny, moving particles

Diffusion in gases

Diffusion of bromine gas

Diffusion of red-brown bromine gas

Description:

  • Here, we see the diffusion of bromine gas from one gas jar to another

  • After 5 minutes the bromine gas has diffused from the bottom jar to the top jar

Explanation: 

  • The air and bromine particles are moving randomly and there are large gaps between particles

  • The particles can therefore easily mix together

Diffusion in liquids

Diagram to show the diffusion of potassium manganate in water

Diffusion of potassium manganate(VII) in water over time

Description:

  • When potassium manganate (VII) crystals are dissolved in water, a purple solution is formed

  • A small number of crystals produce a highly intense colour

Explanation: 

  • The water and potassium manganate (VII) particles are moving randomly and the particles can slide over each other

  • The particles can therefore easily mix together

  • Diffusion in liquids is slower than in gases because the particles in a liquid are closely packed together and move more slowly

Dilution

Diagram to show the dilution of potassium manganate in water.

Dissolving potassium manganate (VII) in water

Description:

  • When potassium magnate (VII) crystals are dissolved in water, the solution can be diluted several times

  • The colour fades but does not disappear until a lot of dilutions have been done

Explanation:

  • This indicates that there are a lot of particles in a small amount of potassium manganate (VII) and therefore the particles must be very small

Examiner Tip

Diffusion and dilution provide evidence for the kinetic theory of matter.

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