The container that cools just right

Sub: Science and Tech

Sec: Msc

Evaporation of water

The molecules of any liquid are in constant motion but all of them don’t move with the same speed. Their energies vary over a small range and the temperature we measure represents only the average kinetic energy of all the molecules.
Even when left undisturbed, the fast-moving molecules escape from the surface and vanish into air. As a result, the mean kinetic energy or the temperature of the water is lowered.
This process is facilitated by a large surface area as more molecules come into contact with air.

How does water stored in a mud pot remain cool?

The pores in mud pots provide a large surface area for evaporation and significantly cool the water in the pot, especially when the temperature outside is higher.
Interestingly, the water in the pot can never become ice. This is because the pitcher is not a closed system: it can also take up heat from its surroundings.
Thus, an equilibrium temperature is reached when the process of heat loss and gain are balanced.
Further conversion of water (even at 0^o C) into ice would require a further removal of heat to bring about a phase change. This will only be possible by using a refrigerant.