Evaporation is the process by which a liquid changes into a gas or vapor state at a temperature below its boiling point. It occurs when the particles of a liquid gain enough energy to break free from the attractive forces of the liquid state and escape into the surrounding atmosphere. Evaporation is a natural phenomenon that happens continuously, even at room temperature.

Factors Affecting Evaporation:
1. Temperature: The rate of evaporation increases with an increase in temperature. This is because as the temperature rises, the particles of the liquid gain more energy and move faster, leading to more collisions and escape of particles into the gas phase.

2. Surface Area: Evaporation is directly proportional to the surface area of the liquid. A larger surface area provides more space for the liquid particles to escape into the atmosphere, resulting in faster evaporation.

3. Humidity: Humidity refers to the amount of moisture present in the air. The rate of evaporation is inversely proportional to humidity. In a humid environment, the air is already saturated with moisture, making it difficult for the liquid particles to escape into the atmosphere. Therefore, evaporation is slower in humid conditions.

4. Wind Speed: The rate of evaporation is also influenced by the speed of the wind. When there is a breeze, the air around the liquid gets replaced more quickly, resulting in faster evaporation. Wind helps in removing the saturated air layer above the liquid, allowing more particles to evaporate.

Why Does Evaporation Cool a Liquid?
Evaporation cools a liquid because the process requires energy in the form of heat. As the more energetic particles escape from the liquid's surface, they take away heat energy with them. This results in a decrease in the average kinetic energy of the remaining liquid particles, leading to a decrease in temperature.

When we wet our skin with water, the water evaporates and takes away heat energy from our body, making us feel cool. This is the principle behind sweating and its cooling effect on the body. Similarly, when water is sprinkled on the ground or leaves of plants, the evaporation of water molecules absorbs heat from the surroundings, causing a cooling effect.

Overall, evaporation is a natural process influenced by temperature, surface area, humidity, and wind speed. It cools a liquid by removing heat energy as the more energetic particles escape into the gas phase.