Matter In Our Surrounding

The spreading out and mixing of a substance with another substance due to the motion of its particles is called Diffusion. Diffusion is a property of matter which is based on the motion (or movements) of its particles. Diffusion is fastest in gases and slowest in solids. The rate of diffusion increases on increasing the temperature of the diffusing substance.

Diffusion in Gases:

• The smell of food being cooked in the kitchen reaches us even from a considerable distance.
• The fragrance of burning incense stick (or agarbatti) spreads all around due to the diffusion of its smoke into the air.
• The smell of perfume spreads due to the diffusion of perfume vapours into air.

Diffusion in Liquids:

• The spreading of purple colour of potassium permanganate into water, on its own, is due to the diffusion of potassium permanganate particles into water.
• The spreading of blue colour of copper sulphate into water, on its own, is due to the diffusion of copper sulphate particles into water.
• The spreading of link in water, on its own, is due to the diffusion of ink particles into water.
• The carbon dioxide gas and oxygen gas present in air (or atmosphere) diffuse into water (of ponds, lakes, rivers and sea), and dissolve in it.

Diffusion in Solids:

• If two metal blocks are bound together tightly and kept undisturbed for a few years, then the particles of one metal are found to have diffused into the other metal.
• The diffusion of a solid substance into another solid substance is so slow that many people think that diffusion does not take place in solids at all.