The process of evaporation involves changing a liquid into a gas on heating.

Evaporation is a phase transition process in which a liquid changes into a gas or vapor state. This transformation occurs when the temperature of the liquid is increased, resulting in an increase in the kinetic energy of the molecules.

Explanation:
- When a liquid is heated, the energy is transferred to the molecules present in the liquid. This increase in energy causes the molecules to move faster and gain more kinetic energy.
- As the temperature of the liquid increases, the average kinetic energy of the molecules also increases. Some of the molecules at the surface of the liquid gain enough energy to overcome the attractive forces holding them in the liquid phase.
- These molecules escape from the liquid surface and enter the surrounding air as vapor or gas. This process is called evaporation.
- Evaporation is an endothermic process, meaning it requires energy in the form of heat to occur. The heat energy from the surroundings is absorbed by the liquid molecules to break the intermolecular forces holding them together.
- During evaporation, the faster-moving molecules escape, causing a decrease in the average kinetic energy and temperature of the remaining liquid. This is why evaporation is a cooling process.
- Evaporation occurs at all temperatures, but it increases with an increase in temperature. Higher temperatures provide more energy to the liquid molecules, leading to a greater number of molecules escaping from the liquid surface.
- Evaporation is the process responsible for the formation of clouds, as water evaporates from the Earth's surface and rises into the atmosphere.
- It is also the process by which sweat on our skin evaporates, cooling down our bodies.
- Evaporation is a dynamic process, and it continues until the liquid has completely evaporated or reached equilibrium with the surrounding vapor pressure.

In summary, evaporation is the process in which a liquid changes into a gas or vapor state on heating. It occurs when the temperature of the liquid is increased, causing the liquid molecules to gain enough energy to escape from the liquid surface and enter the surrounding air. Evaporation is an endothermic process that is responsible for cooling effects and plays a significant role in various natural processes.