When a body changes from Liquid to gas at a constant temperature, it is called

Hint:When a bowl of water is placed on the gas stove, the water changes to vapour state, but this happens at the temperature called boiling point.
Another example could be, when clothes are kept open to dry, the liquid state of water changes to vapour.

Complete step by step solution:
When a body changes from Liquid to gas at a constant temperature, it is called Evaporation.

Evaporation is defined as the process where the liquid state changes to vapour. This process takes place at a temperature, lower than the boiling point.

Evaporation does not require change in temperature, it can happen even at room temperature or constant temperature.
This is the phenomenon by which water enters the atmosphere.

When water is heated, the molecules of water vibrate at a very fast rate, and move vigorously, such that they escape into the atmosphere. This is how water in liquid state converts itself to vapour state.

Additional Information:
Factors that are responsible for evaporation:
(i) Temperature:
When temperature increases, the rate of vaporization also increases.
Example: A bowl of hot water will evaporate at a faster rate than a bowl of cold water.

(ii) Surface area:
As the surface area increases, evaporation occurs faster.
Example: Water kept in a bowl will evaporate faster than that kept in a glass.

Note:
It is important to note that the temperature at which water evaporates must be lower than boiling point, otherwise it will be referred to as boiling.
Boiling also refers to change of water from liquid state to vapour state, however, the change of state occurs at a particular temperature known as the boiling point.