Water kept in an earthen pot is observed to be less cool on rainy days than in summer. What is the main reason for this difference?

Introduction / Context:
Earthen pots are widely used in many regions to cool drinking water naturally. They work on the principle of evaporation. However, people often notice that water stored in such pots feels less cool during the rainy season than in the hot, dry days of summer. This question tests whether you understand how humidity and evaporation affect the cooling process.

Given Data / Assumptions:

• An earthen pot is porous, allowing some water to seep through and wet the outer surface.
• In summer, the surrounding air is usually hot and relatively dry.
• On rainy days, the air is cooler but contains a high amount of water vapour (high humidity).
• We compare how effectively the pot cools water in summer versus during the rainy season.

Concept / Approach:
Evaporation is a surface phenomenon in which high energy molecules escape from a liquid into the air. Evaporation causes cooling because it removes heat from the remaining liquid. The rate of evaporation depends on temperature, surface area, wind speed and, very importantly, the humidity (moisture content) of the air. When humidity is high, the air is already close to saturation, so it cannot accept much more water vapour, and evaporation slows down. In an earthen pot, less evaporation from the outer surface means less cooling of the water inside.

Step-by-Step Solution:
Step 1: Note that the earthen pot has tiny pores through which water seeps and wets the outer surface. Step 2: In summer, the hot and dry air allows rapid evaporation of this water, which absorbs heat from the pot and the water inside, making the stored water cool. Step 3: During the rainy season, the air has a high percentage of moisture and is much more humid. Step 4: Because the air is nearly saturated with water vapour, the evaporation of water from the pot surface becomes slow. Step 5: With reduced evaporation, less heat is drawn away, so the cooling effect is weaker, and the water in the pot is less cool.

Verification / Alternative check:
Everyday observations support this explanation. Clothes dry quickly on a hot, dry day because evaporation is fast, but they remain damp for longer in humid or rainy weather. The same principle applies to earthen pots. Scientific discussions of evaporation always list “dry air” as a factor enhancing evaporation and “humid air” as a factor reducing it. Options that involve pores closing or rain water blocking them are not consistent with how earthen pots and porous materials behave in practice.

Why Other Options Are Wrong:
The pores in the pot are closed: The pores do not normally close simply because it is rainy; the pot remains porous.

Rain water stops oozing out from the pores: The oozing of water is from inside to outside due to capillary action, not directly controlled by raindrops.
The surface of the pot becomes damp: While the surface may be damp, the key factor is that evaporation from this damp surface is slow due to humidity, which is already captured in option C.

Common Pitfalls:
Learners sometimes imagine mechanical effects like pores being blocked rather than thinking of the evaporation process. Another confusion arises from feeling that rainy weather is cooler, so they expect water to be cooler too, forgetting that evaporation is more important here than air temperature. Always connect “earthen pot cooling” with “evaporation,” and remember that high humidity slows evaporation and therefore reduces cooling.

Final Answer:
Water in an earthen pot is less cool on rainy days mainly because the water that oozes out does not evaporate quickly due to the large percentage of moisture in the air.