The correct option is (a).
Explanation
Evaporation is a surface phenomenon wherein a liquid changes into a vapor state at any temperature below its boiling point. This process requires energy (latent heat of vaporization). When liquid particles absorb this energy from their immediate surroundings or the liquid body itself, it results in a net loss of heat, causing a cooling effect.
Statement 1 is Correct:
Earthen pots have a large number of microscopic pores. Water constantly seeps out through these pores to the outer surface of the pot. This water evaporates by absorbing the necessary latent heat from the pot and the water remaining inside. As heat is withdrawn from the system, the temperature of the water inside the pot decreases.
Statement 2 is Incorrect:
Humidity refers to the amount of water vapor present in the air. On a humid day, the air is already saturated with moisture, which decreases the rate of evaporation. Consequently, sweat does not evaporate fast enough to cool the body effectively. Therefore, we feel uncomfortable and sticky rather than cooler.
Statement 3 is Incorrect:
Acetone is a volatile liquid. When poured on the palm, it evaporates rapidly. To undergo this phase change, acetone particles absorb heat energy from the palm. The loss of heat from the palm results in a cooling sensation, not a heating sensation.
Key Takeaway:
Evaporation causes cooling because the liquid absorbs latent heat of vaporization from the surroundings. The rate of evaporation increases with an increase in surface area, temperature, and wind speed, but decreases with an increase in humidity.