Movement of Particles

• Diffusion is the gradual movement of particles from places where there are lots of them to places where there are fewer of them. It's just the natural tendency for stuff to spread out.
• Potassium Manganate (VII) and Water

  1. If you take a breaker of water and place some potassium manganate at the bottom, the purple colour slowly spreads out to fill the beaker.
  2. The particles of potassium manganate are diffusing out among the particles of water.
  3. It's the random motion of particles in a liquid that causes the purple colour to eventually be evenly spread out throughout the water.
• Potassium Manganate (VII) and Water

  • If you were to add more water to the final purple solution, the potassium manganate particles would spread even further apart and the solution would be less purple. This is called dilution
• Ammonia and Hydrogen Chloride

  1. Aqueous ammonia (NH3) gives off ammonia gas. Hydrochloric acid (HCL) gives off hydrogen chloride gas.
  2. Results in a white ring of ammonium chloride forming in the glass tube.
  3. The NH3 gas diffuses from one end of the tube and the HCL gas diffuses from the other. When they meet, they react to form ammonium chloride.
  4. The ring forms near where the hydrochloric acid was.
  5. This is because the particles of ammonia are smaller and lighter than the particles of hydrogen chloride, so they diffuse through the air more quickly.
• Bromine Gas and Air

  1. Bromine gas is a brown, strongly smelling gas. You can use it to determine diffusion in gases.
  2. Fill half of a gas jar full of bromine gas, and the other half full of air - separate the gases with a glass plate.
  3. When you remove the glass plate, you'll see the brown bromine gas slowly diffusing through the air.
  4. The random motion of the particles means that the bromine will eventually diffuse right through the air.