Question

When is water-vapour formed?

Answer 1

Water vapor is also the Earth's most important greenhouse gas, accounting for about 90% of the Earth's natural greenhouse effect, which helps keep the Earth warm enough to support life. When liquid water is evaporated to form water vapor, heat is absorbed. This helps to cool the surface of the Earth.

Answer 2

Water vapor is also the Earth's most important greenhouse gas, accounting for about 90% of the Earth's natural greenhouse effect, which helps keep the Earth warm enough to support life. When liquid water is evaporated to form water vapor, heat is absorbed. This helps to cool the surface of the Earth.
Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible. Under typical atmospheric conditions,water vapor is continuously generated by evaporation and removed by condensation.
We typically refer to the boiling point of water as 100 degrees Celsius. But really this is only the boiling point at sea level pressure. As pressure decreases, we need lower and lower temperatures in order to evaporate water. If the pressure is low enough, we could even get water vapor directly from ice!