What is Water vapor: Definition and 66 Discussions

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. 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.
Being a component of Earth's hydrosphere and hydrologic cycle, it is particularly abundant in Earth's atmosphere, where it acts as the most potent greenhouse gas, stronger than other 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 is significant in that it can be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects.

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  1. M

    Cooling of water vapor - air mixture to T < 273K

    What happens if you cool the mixture of water vapor and air to the temperature lower than 273 K? Since saturation pressure is higher than 0 some vapor should stay in the air. In the solid form?
  2. J

    How do I get water vapor fraction and pressure?

    Hi Guys, I'm building a numerical Matlab simulation of a thermochemical heat storage device (using zeolites), and need to update the state of water vapor in the device at every time step. My question is, if I have an empty space with water in it, with temperature, pressure, density, etc. all...
  3. A

    Water vapor condensation and freezing

    [b]1. When water vapor is condensing or liquid water is freezing? Homework Equations [b]3. The two are affected by the energy of the sorrounding environment is being absorbed into the water.
  4. I

    A few questions about steam, water vapor, and humidity

    I'm trying to understand the differences (if there are any) between steam, water vapor, and humidity. First of all, is there any difference between the meanings of the terms steam and water vapor? Is there a difference between the terms "gas" and "vapor" in general? Also, I was under the...
  5. F

    Water vapor at approx. 300 degrees Celsius

    Ive heard that at somewhere around 300 degrees Celsius (cant remember the exact number), you can't liquidise it anymore. Is this fact correct? Thanks in advance, fawk3s
  6. E

    Saturation of water vapor in the atmosphere

    So I have a quick question about something I'm a bit confused on. I was under the impression that, unlike liquids, gasses become more saturated in COLDER temperatures, rather than warmer. My geology teacher told us that the WARMER it is in the atmosphere the easier it is for water vapor to...
  7. J

    Standard enthelpy of formation for water vapor

    Homework Statement The standard enthalpy of formation for liquid water is -285.8 kJ / mole. Which of the following could be the standard enthalpy of formation for water vapor? A) -480.7 kJ / mole B) -285.8 kJ C) -241.8 kJ / mole D) +224.5 kJ / mole Homework Equations The...
  8. L

    Diffusion of water vapor in air

    I would like to calculate a diffusion of water vapor in stagnant air. Does anybody know if it is a case of equimolar or nonequimolar diffusion. How one could calculate a diffusion in my case? Which variables is diffusion coefficient dependant on?
  9. E

    Expansion Work in Combustion Reactions: Liquid Water vs. Water Vapor

    Expansion Work -- Still confused. This is more of a general question regarding thermodynamics. If you have a combustion reaction, and it produces either liquid water or water vapor--which case results in higher expansion work? My enthalpy calculations show higher PV work for the reaction with...
  10. C

    MWCNT water vapor amount question

    In order to grow MWCNTs I need to have certain content of water vapor dissolved in the argon gas. The amount of water vapor can be changed with temperature of the water that argon bubbles through. I have Argon entering a flask with water in it. The flow of the argon is 120 ml per min. It makes...
  11. W

    Seeking Peer-Reviewed Studies of Water Vapor Feedback

    One of the key factors in determining the climate sensitivity to the increasing atmospheric concentration of CO2 and other long lived greenhouse gases is the response of water vapor to the relatively small warming induced by these gases. Climate models produce a strong signal of positive water...
  12. A

    Thermodynamics: Water vapor vessel plunged into water ice bath

    Homework Statement A closed rigid vessel contains 0.1 kg of water vapor (steam) at 1 bar and 200 C. The vessel is plunged into a bath containing water and ice. After the vessel cools and reaches equilibrium with the bath, the bath still contains water and ice. a. What is the volume...
  13. G

    Degrees of freedom - molecule of water vapor

    I understand that for H20 in solid form, each atom within the molecule has 6 degrees of freedom; 3 translational and 3 due to potential energy from bonds. Does the number of degrees of freedom change when water changes phase to a vapor?
  14. W

    When hydrogen and oxygen gas combine to form water vapor

    Just took a chemistry test, had a few I wasn't sure of: When hydrogen and oxygen gas combine to form water vapor, what mass of water forms if 10grams of oxygen reacts completely? 2H_2 + O_2 \rightarrow 2H_2O 10 grams of oxygen is .625 moles, and the stoichiometric ratio is 1:2, so...
  15. M

    Concentration of water vapor present at equilibrium

    3 Fe (S) + 4 H2O (g) = Fe3O4 + 4 H2 (g) This equilibrium has a Kc of 4.6 @ 850 degree C. Determine the concentration of water vapor present at equilibrium if the reaction is initiated using 8.00 grams H2 and an excess of iron oxide, fe3O4, in a 16.0 liter container. This is what I...
  16. Greg Bernhardt

    What is the heat of formation of water vapor?

    At standard temperature and pressure, what is the heat of formation of water vapor?
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