Take the tour ×  Can steam (water vapour) exist in a vacuum, and
if so does it look and behave the same as in air? Let's assume
the actual case is a kettle boiling in a vacuum.  Note that I'm
talking about a gas-less vacuum, not truly empty space devoid of
all particles except the water.  share|improve this question add
comment  1 Answer  up vote 2 down vote accepted  Water vapour at
the Earth's surface consists of molecules of water mixed up with
molecules of oxygen and nitrogen. At room temperature 100%
relative humidity is about 20g of water per kilogram of air
(roughly a cubic metre), so about 4 molecules per 100 are water.
To get water vapour in a vacuum you just remove the air
molecules and leave the 20g per cubic metre of water molecules.
Put this way it may sound a bit trite, but to a first
approximation air is an ideal gas so the molecules don't
interact except for hard sphere collisions. That means taking
the air molecules away doesn't have a large effect on the water
molecules. The properties of 2