What is Water vapor?
[[Image:watervapor_cup.jpg|thumb|right|Invisible water vapor over a cup of hot tea. The visible mist is actually liquid water drops.]] {{no sources|date=October 2011}} '''Water vapor''' is [[water]] that is in the [[form]] of a vapor, or [[gas]]. It is a part of the [[water cycle]]. When liquid water is heated to [[boiling point]], 100 °C (212 °F), it turns into vapor. Water vapor can also be produced directly from [[ice]]; this is called [[Sublimation (phase transition)|sublimation]]. [[Steam]] is water vapor, but [[cloud]]s are liquid water. The amount of water vapor in air is called [[humidity]] and it affects [[weather]] [[climate|conditions]]. In the cold, breathing out causes the water vapor in the breath to freeze. Water vapor weighs less than air, thus slightly reduces the lift produced by an aircraft wing. It is also transparent, which means the small [[Drop|droplets]] that look like [[mist]] are actually liquid. Water vapor also is a big cause of the greenhouse effect. It is invisible, but makes visible water when it condenses.{{science-stub}} [[Category:Thermodynamics]] [[Category:Water|Vapor]]