The evaporation of water increases under the following conditions :

Question

Accepted Answer

Explanation:

1. **Why Option 2 is Correct:**
   - **Increase in Surface Area:** When the surface area of water is increased, more water molecules are exposed to the air. This exposure allows more molecules to escape into the air, thus increasing the rate of evaporation. For example, water in a shallow pan evaporates faster than in a tall, narrow glass because of the larger surface area.
   - **Rise in Temperature:** As temperature increases, the kinetic energy of water molecules also increases. This means that more molecules have enough energy to break free from the liquid state and enter the gaseous state, thereby increasing the rate of evaporation. This is why water evaporates faster on a hot day compared to a cold day.

2. **Why Other Options are Incorrect:**
   - **Option 1 (Increase in temperature, addition of common salt):** While an increase in temperature does promote evaporation, the addition of common salt actually decreases the rate of evaporation. Salt increases the boiling point of water and reduces the number of water molecules at the surface, thus hindering evaporation.
   - **Option 3 (Increase in surface area, decrease in temperature):** Although increasing the surface area does promote evaporation, a decrease in temperature reduces the kinetic energy of the water molecules. This reduction in energy means fewer molecules can escape into the air, thus slowing down the evaporation process.
   - **Option 4 (Decrease in surface area, decrease in pressure):** A decrease in surface area reduces the number of water molecules exposed to the air, thereby decreasing evaporation. While a decrease in pressure can increase evaporation, the effect of reduced surface area is more significant in this context, making this option incorrect.

In conclusion, Option 2 is the correct answer because both an increase in surface area and a rise in temperature independently and collectively enhance the rate of evaporation, aligning perfectly with the principles of physical chemistry.