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 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
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
Dissolving potassium manganate (VII) in water
Description:
- When potassium manganate (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.
