Instructables

Is there any difference between Water vapor or steam?

Is there any difference?

Kiteman4 years ago
The difference is purely one of temperature.

Water vapour is the same temperature as the air in which it is spread.

Steam is above the local boiling-point of water (usually taken to be 100°C, but varies with local weather and altitude).

It is also a general assumption that "a cloud of steam" will be largely steam / water vapour, whereas "water vapour" is typically only a few percent of the volume of the air.

Chemically, steam and water vapour are identical.
frollard4 years ago
As a few others say (Re-Design, Kiteman) the key difference is temperature.

Steam is water above boiling point that is allowed to escape as gas.  It only exists at above water's boiling point at a given pressure (100+ degrees C at sea level).  It is individual water molecules bouncing around like a gas.  Note, sometimes steam is referred to as water vapour above boiling temperature.

Water vapour is DIFFUSED water particles, like fog or mist.  It is AIR molecules with tiny tiny water particles floating in it. It exists at temperatures/pressures BELOW boiling point.  When the water particles are condensed it appears as a fog, when they are totally evaporated it is invisible.

When your kettle boils and 'steam' comes off the boiling water, it quickly hits cold air and condenses into a cloud of water vapour + steam, then totally evaporates

References: http://dictionary.reference.com/browse/water+vapour
http://dictionary.reference.com/browse/steam
necropolian (author)  frollard4 years ago

Thus, it would be right to assume water vapor is not actually a gas, but just very tiny water drops, and steam is the only true gas state of H²O?

in the most true sense yes.
framistan4 years ago
When WATER VAPOR comes off of a "STEAM KETTLE"  it is relatively low temperature (the temperature of water boiling) I believe that is about 212 degrees F.  If you work with STEAM ENGINES such as on steamships or locomotives... then STEAM is a TECHNICAL  term for MUCH HIGHER TEMPERATURE water vapor that can be hundreds of degrees hot.  TRUE steam is very hot and it is invisible and it can kill you if you breathe it.  I think the misunderstanding comes from the users of kitchen "steam" kettles are not concerned with technical terminology used by engineers who build steam powered engines.  The proper name for the kitchen appliance should be a water-vapor-kettle.  While we are correcting the improper names of things we should also stop calling your water heater a HOT water heater... because to be accurate... it is a COLD water heater.
I learned this by watching a show on tv about steam engines. 
No, think about how water evaporates from a puddle. Do you see clouds of fog ? No, water molecules are aquiring enough energy to escape from the liquid state to the gaseous state. They have a lot less energy than the gas evolved at 100 C +, but they are still gas.


Also, if you look PROPERLY at the output of a boiling kettle, LIVE steam is "invisible" between the spout and the formation of the condensate cloud.
Re-design4 years ago
Water vapor is water that is in a gaseous state and steam is water that has been heated to the boiling point.  You can't see steam it is invisible.  What you see rising out of a tea kettle is steam that has condensed and is no longer steam.   It's "fog" at that point.
Water vapor is the gaseous state of water Steam is similar i believe (not 100% sure if its the same thing)
cj814994 years ago
i dont think so