Evaporation is the scientific process that causes the level of water to go down as it is heated. Evaporation is the process by which liquid water changes into water vapour. This process occurs when the water molecules gain enough energy to overcome the forces that hold them together and escape into the atmosphere.

The rate of evaporation increases as the temperature of the water increases. This is because the water molecules have more energy at higher temperatures and are therefore more likely to escape from the liquid.

Evaporation is also affected by the humidity of the air. The higher the humidity, the less likely water molecules are to escape from the liquid because there are already a lot of water molecules in the air.

Evaporation is an important process in the water cycle. It is responsible for the movement of water from the Earth's surface to the atmosphere.