Water vapor

Water vapor, water vapour or aqueous vapor is the gaseous phase of water.

It is the most abundant substance on Earth and the only common substance to exist as a solid, liquid, and gas on Earth's surface.

Being a component of Earth's hydrosphere and hydrologic cycle, it is particularly abundant in Earth's atmosphere where it is also a potent greenhouse gas along with other gases such as carbon dioxide and methane.

The primary greenhouse gases in Earth's atmosphere are water vapor (H 2 O), carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and ozone (O 3 ).

Use of water vapor, as steam, has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution.

Steam is water vapor, which is water in the gas phase.

Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice.

It may also be deposited directly by water vapor, as happens in the formation of frost.

Being a component of Earth's hydrosphere and hydrologic cycle, it is particularly abundant in Earth's atmosphere where it is also a potent greenhouse gas along with other gases such as carbon dioxide and methane. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds.

Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice.

In the atmosphere at ordinary temperatures, therefore, gaseous water (known as water vapor) will condense into a liquid if its partial pressure is increased sufficiently.

Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice.

Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen.

Humidity is the amount of water vapor in the air.

Humidity is the concentration of water vapour present in air.

The vapor content of air is measured with devices known as hygrometers.

A hygrometer is an instrument used to measure the amount of humidity and water vapour in the atmosphere, in soil, or in confined spaces.

It is one state of water within the hydrosphere.

The total mass of Earth's hydrosphere is about 1.4 × 10 18 tonnes, which is about 0.023% of Earth's total mass. At any given time, about 20 × 10 12 tonnes of this is in the form of water vapor in the Earth's atmosphere (for practical purposes, 1 cubic meter of water weighs one tonne).

It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds. For example, latent heat release in atmospheric convection is directly responsible for powering destructive storms such as tropical cyclones and severe thunderstorms.

It consists of two primary convection cells, the Hadley cell and the polar vortex, with the Hadley cell experiencing stronger convection due to the release of latent heat energy by condensation of water vapor at higher altitudes during cloud formation.

Water vapour will only condense onto another surface when that surface is cooler than the dew point temperature, or when the water vapour equilibrium in air has been exceeded.

The dew point is the temperature to which air must be cooled to become saturated with water vapor.

Frost and snow are examples of deposition.

Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) to ice (a solid) as the water vapor reaches the freezing point.

In the atmosphere, condensation produces clouds, fog and precipitation (usually only when facilitated by cloud condensation nuclei). Fog and clouds form through condensation around cloud condensation nuclei.

When no CCNs are present, water vapour can be supercooled at about −13°C (8°F) for 5–6 hours before droplets spontaneously form (this is the basis of the cloud chamber for detecting subatomic particles).

Dew point temperature and relative humidity act as guidelines for the process of water vapor in the water cycle.

In doing so, the water goes through different forms: liquid, solid (ice) and vapor.

Approximately 99.13% of it is contained in the troposphere.

It contains 75% of the atmosphere's mass and 99% of the total mass of water vapour and aerosols.

In some countries, the evaporation rate far exceeds the precipitation rate. The condensation of water vapor to the liquid or ice phase is responsible for clouds, rain, snow, and other precipitation, all of which count among the most significant elements of what we experience as weather.

In meteorology, precipitation is any product of the condensation of atmospheric water vapour that falls under gravity.

The condensation of water vapor to the liquid or ice phase is responsible for clouds, rain, snow, and other precipitation, all of which count among the most significant elements of what we experience as weather.

On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature.

Remote methods such electromagnetic absorption are possible from satellites above planetary atmospheres.

The presence of water vapor in the atmosphere is important for atmospheric chemistry especially as the infrared and near infrared spectra are easy to observe.

Deposition is a phase transition separate from condensation which leads to the direct formation of ice from water vapour.

One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid.

Forcibly condensing these water droplets from exhaled breath is the basis of exhaled breath condensate, an evolving medical diagnostic test.

It has long been appreciated that the exhaled breath is saturated by water vapour (e.g. by wind musical instrument players), but using it for studies of the lung was probably first described in the Russian scientific literature.

Fog and clouds form through condensation around cloud condensation nuclei.

Fog begins to form when water vapor condenses into tiny liquid water droplets that are suspended in the air.

For example, latent heat release in atmospheric convection is directly responsible for powering destructive storms such as tropical cyclones and severe thunderstorms.

However, water vapor is consistently the commonest volcanic gas; as a rule, it comprises more than 60% of total emissions during a subaerial eruption.

The principal components of volcanic gases are water vapor (H 2 O), carbon dioxide (CO 2 ), sulfur either as sulfur dioxide (SO 2 ) (high-temperature volcanic gases) or hydrogen sulfide (H 2 S) (low-temperature volcanic gases), nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen.

As this coating absorbs incoming water vapor, an electrical potential is applied to the windings that electrolyzes the water to hydrogen and oxygen.