The process by which a liquid transforms into a gas at the liquid's surface is known as evaporation. It is a form of vaporization that occurs when the molecules of a liquid absorb enough energy to overcome the force holding them together and break free from the liquid's surface to become airborne as individual molecules.

Evaporation is driven by several factors:

1. Temperature: As the temperature of a liquid rises, the kinetic energy of its molecules increases, leading to more frequent and energetic collisions. This increase in energy allows molecules to escape from the liquid phase more easily, resulting in a higher rate of evaporation.

2. Surface area: The larger the surface area of the liquid, the more molecules are exposed to the surrounding environment and have the opportunity to evaporate. This is why a shallow pan of water evaporates faster than a deep one.

3. Humidity: The amount of water vapor already present in the air affects the rate of evaporation. If the air is humid (contains a lot of water vapor), the rate of evaporation decreases because the water molecules in the air compete with those from the liquid for space.

4. Air movement: Moving air, like wind, helps to carry away water vapor from the surface of the liquid, creating a concentration gradient that promotes further evaporation. This is why clothes dry faster on a windy day compared to a still day.

Evaporation is a continuous process that occurs at all temperatures above absolute zero, but it becomes more noticeable as the temperature increases and the conditions favour the escape of molecules from the liquid phase into the gaseous phase.