What is diffusion?
Diffusion is the process by which molecules from higher concentration move to lower concentration until they are evenly distributed and an equilibrium is reached. It is a process of mixing of one component into another.
We can observe diffusion in many day to day activities.Dialysis, osmosis, mixing of dye and air in water, etc are common examples of diffusion.
An experiment to observe diffusion:
Take a beaker and fill it with water. Put a crystal of potassium permanganate into it. The colour of the crystal slowly spreads throughout the water. This occurs due to diffusion.
We can also observe water bubbles in water as a result of diffusion of air into water, or diffusion is also observed when smoke from an incense stick placed far away diffuses with air and travel to our noses.
We also observe that when a matter is heated, the process of diffusion increases. We can observe it when we note that the solubility of sugar in water is much higher and faster at a higher temperature.
Diffusion in solids, liquids and gases:
Particles in a matter are constantly in motion due to their kinetic energy. Due to this, diffusion can occur in all the three forms of matter. It can occur in both similar as well as different types of matter.
It occurs slowest in solids and fastest in gases.
Diffusion in solids:
The process of diffusion is slowest in the solids. For example gold diffuses into lead, salt diffuses into water, etc.
Diffusion in liquids:
Diffusion in liquids plays an important role in supporting the aquatic life. The important gases from the atmosphere, like oxygen and carbon dioxide get diffused in water bodies and are used by the aquatic organisms for their survival.
The process of diffusion in liquids is slower than that of gases.
Other than gases, liquids also diffuse solids and other liquids in them.
Diffusion in gases:
Since the gas particles have a lot of kinetic energy and a random motion in all directions, the rate of diffusion in gases is very high. We have observed many times that when food is cooked, the aroma of the food mixes with the air particles around it and reaches our nose. This happens because diffusion due to high kinetic energy of gas particles.
NCERT Solutions related to the topic “Diffusion in solids, liquids and gases” – NCERT Textbook Page 12
Question 3. Give reasons for the following observations.
(b)We can get the smell of perfume sitting several metres away.
Answer. Aromatic gases coming out from perfume diffuse with the gases of the surroundings and can travel very far. Hence, we get the smell of perfume sitting very far.