Question

During summer season, water kept in an earthen pot becomes cool because of the phenomenon of :
a.) diffusion
b.) transpiration
c.) osmosis
d.) evaporation

Answer 1

Hint: The earthen pots have small holes and the water keeps on coming out of it which evaporates. The water requires some energy so that the liquid molecules could turn into vapours. This energy is provided by the water in the pot which results in lowering of its temperature.

Complete step by step answer :
First, let us see all these phenomena. Then, we will be able to find the correct answer.
The first process is diffusion. It is the phenomenon of moving particles from regions of higher concentration to regions of lower concentration. For example – Addition of ink in water leads to colouring of water.
The second process is the transpiration. It is the process that occurs in plants by which they exhale water vapor through stomata.
The third process is the osmosis. It is the phenomenon of moving solvent particles across a semipermeable from a region of low solute concentration to more solute concentration. For example - Red blood cells swell up when exposed to water.
The fourth process is the evaporation. It is the process of conversion of surface liquid into the vapours slowly without use of outer energy. For example - The clouds are formed from evaporation of water from the sea surface.
Now, as we know all these processes, we can differentiate between them and find out the correct option.
The earthen pots are made up of soil and during their formation, some holes are left as such in the soil. The water comes out of these holes in a very minute quantity. This water then gets evaporated from the surface of the pot. The energy required for this to evaporate is provided by the water present in the pot. Thus, by giving energy, the water gets lowered in state and as a result, gets cooled down.
So, the evaporation is responsible for cooling of water in the earthen pot.

Thus, the option d.) is the correct answer.

Note: It must be noted that during the formation of pot, the soil particles are very tightly packed but still some of the pores are left. These pores are not visible with naked eye and neither do they lead to flow of water outside the pot. They are so small such that only a few drops of water could come out of them.