This article is about water as a gas. For the video game distribution platform, see Steam (service). For other uses, see Steam (disambiguation). Water in the gas phase Liquid phase eruption of Castle Geyser in Yellowstone Park A temperature-versus-entropy diagram for steam A Mollier enthalpy-versus-entropy diagram for steam

Steam is water in the gas phase. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Steam that is saturated or superheated is invisible; however, "steam" often refers to wet steam, the visible mist or aerosol of water droplets formed as water vapour condenses.

Water increases in volume by 1,700 times at standard temperature and pressure; this change in volume can be converted into mechanical work by steam engines such as reciprocating piston type engines and steam turbines, which are a sub-group of steam engines. Piston type steam engines played a central role in the Industrial Revolution and modern steam turbines are used to generate more than 80% of the world's electricity. If liquid water comes in contact with a very hot surface or depressurizes quickly below its vapor pressure, it can create a steam explosion.


Types of steam and conversions

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