What is Diffusion?
Spreading out and Mixing
of one substance with other is called Diffusion
It happens in all forms of matter - Solids, Liquids and Gases
It is fastest in gases and slowest in solids
Examples of Diffusion in Gases
Example 1
- We take 2 gas jars, one contains brown coloured bromine gas and other containing air (which is colourless)
- Now we invert gas jar containing bromine gas over gas jar containing air
- After some time, we observe both gas jar become brown in color
- This is because of diffusion (spreading out or mixing) bromine gas in air
Example 2
The smell of cooked food reaches our nose because of the diffusion of food gas in the air
Example 3
The smell of perfume/incense stick (agarbatti) reaches us because of diffusion of perfume gas in the air
Examples of Diffusion of Liquids
Example 1
If a drop of ink is put in a jar of water, the colour soon spreads to the whole of the jar
This is due to the diffusion of ink particles i n water
Example 2
If a crystal of Potassium Permanganate is put in a jar of water
Then whole water soon turns into a purple colour
This is due to the diffusion of potassium permanganate in water
Example 3
Aquatic Animals used dissolved oxygen in the water to breathe
Aquatic plants use dissolved carbon dioxide in water for photosynthesis
This is due to the diffusion of oxygen and carbon dioxide particles in water
Examples of Diffusion in Solids
Diffusion in solids is slowest and takes a lot of time
Example
If we write something on the blackboard and do not erase it for a long period of time
The chalk particles get diffused with particles of blackboard
Hence we find it difficult to erase
Example 2
If 2 metal blocks are bound together and kept for a few years
Particles of both box mix with each other
Comparison - Diffusion in Solids, Liquids and Gases
| Solids | Liquid | Gases |
| Diffusion is slowest in Solids | Diffusion is fast compared to solids but slow compared to liquids | Diffusion is fastest in gases |
