Question

During summer, water kept in an earthern pot becomes cool because of the phenomenon of :

• A. diffusion
• B. transpiration
• C. osmosis
• D. evaporation

Hint:

Evaporation needs heat. When water evaporates from the surface of an earthen pot, it takes heat from the pot and the water inside. This removal of heat makes the remaining water cooler. It's similar to how sweating cools your body – the sweat evaporates, taking heat from your skin.

Answer 1

The Correct Option is D

Concept: The cooling effect observed in water stored in earthen pots (like a matka or surahi) is due to a specific phase change process that requires energy. Step 1: Properties of an earthen pot Earthen pots are porous, meaning they have very tiny, microscopic pores or holes in their walls. Step 2: The process occurring Water kept inside the earthen pot seeps out through these tiny pores to the outer surface of the pot. On the outer surface, this water comes into contact with the surrounding air. The water on the outer surface undergoes evaporation. Evaporation is the process where a liquid changes into its vapor (gas) phase at a temperature below its boiling point. Step 3: How evaporation causes cooling Evaporation is an endothermic process, meaning it requires energy (heat). The molecules of water that evaporate from the surface take this energy (latent heat of vaporization) from:
The remaining water on the surface of the pot.
The pot itself.
Ultimately, from the water inside the pot. As this heat energy is continuously removed from the system (pot and water inside) to fuel the evaporation, the temperature of the water inside the pot decreases, making it cool. Step 4: Analyzing other options
(1) Diffusion: The movement of particles from an area of higher concentration to lower concentration. While involved in vapor movement, it's not the primary cooling mechanism.
(2) Transpiration: The process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Not relevant to an earthen pot.
(3) Osmosis: The movement of solvent (like water) across a semipermeable membrane from a region of low solute concentration to high solute concentration. Not the primary cooling mechanism here. The cooling is directly caused by the energy absorbed during evaporation.