It is called water vapour or simply vapour.
Water vapor
steam
steam
water vapour
'When liquid water changes to an invisible gas it is called evaporation. The water is turned into water VAPOUR. You can remember this by remembering the word vapour in eVAPOURation.
The gas valve for the water heater should be turned on when you need hot water and off when you do not need hot water.
If your gas gets turned off, you may not have hot water available because most water heaters rely on gas to heat the water.
Evaporate
evaporation
Evaporation
Evaporation
it is called evaporatin