DIFFUSION

  

The intermixing of particles of two different type of matter on their own is called diffusion.

 Particles of matter have space between them, so particles of other matter can occupy that space resulting in intermixing of particles of different matters.

Examples of diffusion 

1. Using a lighter, light an incense stick (agarbatti) and put in the corner of a room. After sometime smell of the incense stick can be sensed all over the room because air particles filled in the room is loosely packed have a lot of space between them, so particles of vapours coming out from the incense stick will occupy that space and spread all over the room.

2. Put a crystal of potassium permanganate into  two glasses, one with hot water and other containing cold water. Allow the crystals to settle at the bottom (do not stir the solution). We can observe just above the solid crystal in each glass purple colour started spreading in water this is because of particles in potassium permanganate occupies space between the water particles and spreading slowly (even without stirring particles are spreading because particles of matter are always in continuous motion)

       But spreading of potassium permanganate particles is more intense in hot water that cold water because in hot water, kinetic energy of particles is more compared to particles of cold water due to gaining of heat energy. From this we can understand rate of diffusion increases with increase in temperature.