Invisible water vapor condenses to form visible clouds of liquid rain droplets
Liquid state
Water
Solid state
Ice
Properties[1]
Molecular formula
H2O
Molar mass
18.01528(33) g/mol
Melting point
0.00 °C (273.15 K)[2]
Boiling point
99.98 °C (373.13 K)[2]
Specific gas constant
461.5 J/(kg·K)
Heat of vaporization
2.27 MJ/kg
Heat capacity at 300 K
1.864 kJ/(kg·K)[3]
Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor is transparent, like most constituents of the atmosphere.[4] Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds and fog.
Being a component of Earth's hydrosphere and hydrologic cycle, it is particularly abundant in Earth's atmosphere, where it acts as a greenhouse gas and warming feedback, contributing more to total greenhouse effect than non-condensable gases such as carbon dioxide and methane. Use of water vapor, as steam, has been important for cooking, and as a major component in energy production and transport systems since the industrial revolution.
Water vapor is a relatively common atmospheric constituent, present even in the solar atmosphere as well as every planet in the Solar System and many astronomical objects including natural satellites, comets and even large asteroids. Likewise the detection of extrasolar water vapor would indicate a similar distribution in other planetary systems. Water vapor can also be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects.
Water vapor, which reacts to temperature changes, is referred to as a 'feedback', because it amplifies the effect of forces that initially cause the warming.So, it is a greenhouse gas.[5]
^Lide (1992)
^ abVienna Standard Mean Ocean Water (VSMOW), used for calibration, melts at 273.1500089(10) K (0.000089(10) °C) and boils at 373.1339 K (99.9839 °C)
^"Water Vapor – Specific Heat". Retrieved May 15, 2012.
^"What is Water Vapor?". Retrieved August 28, 2012.
Watervapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Watervapor can be produced...
The vapor pressure of water is the pressure exerted by molecules of watervapor in gaseous form (whether pure or in a mixture with other gases such as...
temperatures gaseous water (known as watervapor) will condense into a liquid if its partial pressure is increased sufficiently. A vapor may co-exist with...
Humidity is the concentration of watervapor present in the air. Watervapor, the gaseous state of water, is generally invisible to the human eye. Humidity...
Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid)...
of water is steam or watervapor. Water covers about 71% of the Earth's surface, with seas and oceans making up most of the water volume (about 96.5%)...
are also easily observed in the near-infrared region. The presence of watervapor in the atmosphere is important for atmospheric chemistry especially as...
flow. In doing so, the water goes through different forms: liquid, solid (ice) and vapor. The ocean plays a key role in the water cycle as it is the source...
Earth's surface. They are composed primarily of water, in the form of ice crystals. The combination of watervapor in aircraft engine exhaust and the low ambient...
vapor retarders as having a watervapor permeance of 1 perm or less when tested in accordance with the ASTM E96 desiccant, or dry cup method. Vapor-retarding...
Moisture vapor transmission rate (MVTR), also watervapor transmission rate (WVTR), is a measure of the passage of watervapor through a substance. It...
positive feedback is that warming increases the amount of atmospheric watervapor, which is a powerful greenhouse gas. Another positive feedback is the...
atmosphere, listed in decreasing order of average global mole fraction, are: watervapor, carbon dioxide, methane, nitrous oxide, ozone. Other greenhouse gases...
An atmospheric water generator (AWG), is a device that extracts water from humid ambient air, producing potable water. Watervapor in the air can be extracted...
appears when water vapor (water in its gaseous form) condenses. During condensation, molecules of watervapor combine to make tiny water droplets that hang...
nitrogen and oxygen. Watervapor is widely present in the atmosphere, forming clouds that cover most of the planet. The watervapor acts as a greenhouse...
Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form watervapor; this vapor can then rise up...
Watervapor windows are wavelengths of infrared light that have little absorption by watervapor in Earth's atmosphere. Because of this weak absorption...
{\displaystyle p_{\text{v}}} , pressure of watervapor (Pa) R v {\displaystyle R_{\text{v}}} , specific gas constant for watervapor, 461.495 J/(kg·K) M d {\displaystyle...
it must be cooled to become saturated with watervapor. This temperature depends on the pressure and water content of the air. When the air is cooled...
temperature, bacteria, etc. Barrier protection - A barrier from oxygen, watervapor, dust, etc., is often required. Permeation is a critical factor in design...
may be used to monitor global temperature variations and variations of watervapor in the upper troposphere. Schumann resonances have been used to study...
column of rising water is exposed to the near-vacuum of the surface of most icy bodies, it will immediately start to boil, because its vapor pressure is much...
produced in a boiler that heats tap water to high temperatures to produce low-pressure, low moisture watervapor. The steam cleaner's ability to clean...
be deposited directly by watervapor as frost. The transition from ice to water is melting and from ice directly to watervapor is sublimation. These processes...
small amounts of other gases. Air also contains a variable amount of watervapor, on average around 1% at sea level, and 0.4% over the entire atmosphere...
phase of water is known as watervapor (or steam). Visible steam and clouds are formed from minute droplets of water suspended in the air. Water also forms...
stomatal pore, watervapor will travel down the gradient and move from the leaf airspace to the atmosphere. This movement lowers the water potential in...
meteorology, precipitation is any product of the condensation of atmospheric watervapor that falls from clouds due to gravitational pull. The main forms of precipitation...
humidity or dampness. Permeation of water vapour through a material or structure is reported as a moisture vapor transmission rate (MVTR). The hulls of...
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