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. samy4408

    Trying to understand alveolar surface tension

    Hello, I learned recently about alveolar surface tension, and the explanation provided in the course was not satisfactory, it said that it is due to the force that pushes water molecules of the outer layer to the inner layers, I don't understand why this force that pushes water toward the cell...
  2. Optymista93

    Cleaning of the finned tubes on gas cooler without disassembling

    Hi, I've been thinking about the solution for cleaning a water-cooled gas cooler and would love to hear some advice from the smarter people with more experience. Description - I will try to roughly explain the concept. Gas Cooler is used to decrease exhaust gas temperature. The exhaust gas...
  3. M

    I Water bath and water vapor + air mixture in a closed system

    Hello, At my work I came up with the following question: Say we have a vacuum chamber. Inside the vacuum chamber we have at the bottom a water bath. The rest of the chamber is filled with a air and water vapor mixture. The whole system is placed in a room, is at room temperature and is in...
  4. jaumzaum

    Why can shock waves condense water vapor?

    Why can a shock wave condensate water droplets in the air and produce the visible vapor cone that we see when objects move faster than the speed of sound. Also, does this condensation happens only when the object is moving with a velocity greater than sound velocity? I don't understand the...
  5. M

    Optical Laser to refract/reflect water vapor and smoke.... angles?

    Building visibiity sensor... What is best angle to detect water vapor reflection from laser, and refraction? I plan to have two open cylindrical containers painted flat black and put inside each other so the overlap is about 0.5-1" (adj to limit ambient light vs airflow). Laser is cheap red...
  6. D

    Calculate the amount of water vapor

    Hello 4m3/min is 240m3 /hr. Temperature is 293K, at 25C the amount of water is 22.8g/m3 and at 20C it is 17.1g/m3. Relative humidity is 70% and absolute pressure 9bar. Solution: @ 25C relative humidity lowers the water content from 22.8 to 15,96g/m3 so in total 3830.4g/hr 240m3 or air is...
  7. M

    Water vapor absorption in THz range

    Hi everyone! Terahertz time-domain spectroscopy (THz-TDS) is a spectroscopic technique that is using the radiation in the THz range. https://en.wikipedia.org/wiki/Terahertz_time-domain_spectroscopy A THz-TDS setup consists of an emitter and detector. The emitter creates a short broadband...
  8. Jed K

    How does water vapor in the atmosphere form under normal conditions?

    So I understand generally how humidity in atmospherics work but there's this one thing I can't reconcile with the fundamentals. First, my understanding of the basics. Water boils at 212 F @ 14.7 psia (1 ATM). At 213F @ 14.7 psia that water is now 1F superheated vapor. So we're all on the same...
  9. P

    Where can I find water vapor images?

    I am searching for images of the daytime sky taken within the water vapor absorption bands at 940nm, 1600 nm, 1860 nm, 2700 nm or 2900 nm. Specifically I am trying to see if multispectral images of in-band and adjacent out-of-band photos could be subtracted to show areas of slight water vapor...
  10. N

    Can water vapor go directly into a solid

    If water vapor is pulled inwards and cooled at a fast enough rate could if be frozen back into a solid form? i understand that they would have to be froze together as soon as contact is made but if this is possible what would the temperature have to be? And could this be the only thing that can...
  11. K

    How to calculate : Mass flow of water vapor in the air (kg/h)

    Hello Homework Statement Lets say i have the given parameters: air volume flow : V = 36 m3/h Relative humidity: RH=33% air mixing ratio : X = 5.5 (1g H2O) / 1kg (DRY AIR) (calculated from RH) air temperature : T= 20 C So i know how much mass of water is the air compared to the air's "dry air"...
  12. A

    Could you create thrust with water vapor?

    Whilst I was thinking of hydrogen combustion jet engines. I thought of a little idea... What if you could create thrust with water vapor the same way you could with the exhaust gas of a jet engine. (NOTE: I have no experience in engineering and I only have a mild interest in it). If this is...
  13. Z

    Gas Law applying to air vs water vapor

    Say we have a tire filled with air (equal to ambient air surrounding it in every way). pressure on the gauge is 0. Then, we pressurize it to 1 ATM (15psi). If we heat the tire , the air will be heated and expand based on gas law, or is there a factor that changes it based on the air's...
  14. Ravi Singh choudhary

    Gibbs phase rule use for wet vapour

    I have a doubt regarding gibbs phase rule in thermodynamics.. It says the number of independent intensive properties required to specify the state of a system is F=C-P+2 where C is number of components and P is the number of phase.. So for a water and water vapour system, C=1, P=2 . So F=1. If...
  15. grandpa2390

    Why does Water Vapor have 12 degrees of freedom?

    Homework Statement How many degrees of freedom does water vapor have Homework Equations Translational up to 3 rotational up to 3 Vibration up to 6 The Attempt at a Solution Well I said water vapor had 3 translational. It can move along the x, y, or z axis I said it had 2 rotational (the...
  16. A

    Vapor Pressure In Closed Cylinder

    Hi There, I am trying to understand if I have a vacuum in the below scenario or simply just really low pressure. A pump supplies a pipe with a constant supply of water at one end (Point A) the water discharges several kilometers away at some lower elevation (Point B). At "Point A" a valve...
  17. B

    Ice sublimating to water vapor

    Suppose an ice cube is in a vessel and it is at a temperature slightly below 0 degrees Cesius. Suppose further that the inside of the vessel is a vacuum. If the temperature of the vessel is increased to slightly above zero Celsius and the vacuum is maintained would the state change in the ice...
  18. D

    Permeation of water vapor through seals: vacuum vs dry gas

    From reading about the permeation of gasses through polymer seals, I am led to believe that given two identical sealed chambers, one containing a vacuum and the other pressurized perfectly dry nitrogen, water vapor would permeate through the seals and into the chambers at the same rate. This...
  19. L

    Nylon deterioration from hydrogen released water vapor?

    Hello, I am by far not very firmiliar with physics nor engineering. I had an idea a couple years ago involving the replacement of the propane in hot air balloons with hydrogen gas as the fuel to burned to provide the heat to lift the balloon. One thing I didn't realize back then was that...
  20. K

    Does Condensation of Water Vapor Constitute Heat Transfer?

    Scenario A: An icicle on the eaves of Uncle Ivan’s dacha in far off Verkhoyansk vaporizes a number of water vapor molecules at an ambient temperature of -80°C. Over the succeeding months, one of these molecules makes its random way to the surface of a cloud droplet over Ouagadougou. Along the...
  21. Soumalya

    Psychrometrics - Pure Humidification Process

    In psychrometrics it is outlined time and again that we cannot achieve a pure humidification process i.e, add only moisture to unsaturated air without a change in its Dry Bulb Temperature(DBT).While pondering over the idea I came up with a possible way of doing it (if it is correct at all) and...
  22. P

    Solving Psychrometry Questions: Room Temp & Water Vapor

    As we all know that in atmospheric pressure (1 Bar) saturation temperature of water is 100 deg C. And the air contains mixture of dry air and water vapour. My doubt is here that the water needs 100 deg Celsius to change from liquid to vapour state then how can a normal room temperature air...
  23. Tam Le

    Gas State of Liquid Substances: Exploring Water Vapor

    Is it simply the gaseous state of a liquid substance? For instance, water vapor, in this context, would be the gas state of water after having transitioned from a liquid state.
  24. M

    Is there a difference between water vapor and wet steam?

    Both water vapor and wet steam contain both contain tiny droplets of water particles(correct me if I'm wrong).Does it mean both water vapor and wet steam are same and one ?
  25. K

    Partial pressure of water vapor

    Homework Statement The partial pressure of water vapor in air at 200 is 10[mm] mercury. according to the table of partial pressures we have to cool the air to 11.40 in order to bring the air to saturation, that is100% relative humidity. this according to the book. But when we cool the pressure...
  26. W

    Pressure, temp, volume change of water vapor, and steam table clarity

    Homework Statement Two pounds of water vapor at 30 psia fill the 4ft^3 left chamber of a partitioned system. The right chamber has twice the volume of the left and is initially evacuated. Determine the pressure of the water after the partition has been removed and enough heat has been...
  27. M

    Water vapor below 100 degrees?

    hi all My question is: In a pressurized (close to 1.1 atm; B.P. 109 degrees), closed system of water mixed (in a ratio of 1000 lts to 20lts) with Boron Nitrite (yes I am talking about cooling water system for automobiles) where the temp of the mixture does not exceed 96 degrees Celsius; will...
  28. W

    How high can you push water vapor from solarthermal desalination?

    Hi all, Yet another noob question from me... I been thinking of Solarthermal desalination plant lately but I'm surprised that no plan seems to take into account the possibility of letting the vapor rise to a much higher level, thus creating a potential energy source. Is there something...
  29. powerof

    Calorimetry: mix of ice, water vapor inside a copper container

    Homework Statement We insert into a copper container (weighing 1.5 Kg) 3 Kg of water vapour at 100 ºC. Inside the container there are 10 Kg of ice at -10ºC. Find the ΔT when the system reaches the equilibrium. Known data: the specific heats of water, copper and ice and the latent heat of...
  30. A

    How can i separate water vapor from biogas

    Hi I need to know how i can separate the water vapor from biogas i know that there is separation of H2S and Co2 but what the procedure to remove water vapor from biogas ? thank you :)
  31. A

    Calculating Water Vapor Requirements for Temperature Change of a System

    Homework Statement How much water vapor (100 ° C) should be added to 120 g of ice (0 ° C) so that the final system has a final temperature of 35° C. Homework Equations Qvapor = lvapor * mvapor during condensation, where lvapor =2260 kJ/kg Q1 = cwater*mvapor*ΔT during cooling, and...
  32. S

    Medical (Respiration) how water vapor affects barometric pressure

    hello folks, let me apologize if this was addressed before, but every time I try to search for partial pressure of oxygen and water, I get problems unrelated to mine. I also searched Wikipedia and Google and found their explanations a bit too obtuse. But it's possible I'm just doing a bad job...
  33. marcus

    Water vapor observed venting from Ceres

    http://www.bbc.co.uk/news/science-environment-25849871 Herschel space telescope press release: http://sci.esa.int/herschel/53125-herschel-discovers-water-vapour-around-dwarf-planet-ceres/ Abstract of scholarly article published in Nature...
  34. C

    Latent heat in water vapor below boiling

    Hi - I'm a physics newbie so this is an elementary question, but I can't find the answer with a google search. Water evaporates at a wide range of temperatures, what is the latent heat in the water vapor (in calories or Joules), for example, at 30°C, 60°C? Assume standard atmospheric...
  35. R

    How to find water vapor volume at different pressures than atm?

    Homework Statement If a known amount, let's say 300 liters of water gas (water vapor) is flowing from an atmospheric (14.7 psi) source/chamber, into a chamber of reduced pressure of 10 psi, does the volume amount and/or moles change? Homework Equations So I believe I would multiply the...
  36. R

    How are the satellites that detect water vapor made?

    How are the satellites that detect water vapor made? What goes into them that allow companies such as NOAA to create those water vapor images?
  37. skate_nerd

    How would water vapor contamination affect PV=nRT

    Homework Statement Doing a lab here, but were kind of stuck. This lab is meant to experiment the formula PV=nRT, and the set up is a canister of CO^2 with a fixed volume that has a pressure sensor connected to it reading in pascals. We heat up the CO^2 by placing the canister in a beaker of...
  38. F

    Separate water vapor from atmospheric air

    There is a simple method to separate the water vapor from the atmospheric air, however, in the form of gas and not of condensed water?
  39. A

    Thermodynamics: Cooling Superheated Water Vapor to Saturated Vapor

    Superheated H20 at 400 kPa is slowly cooled in a sealed rigid vessel until the temperature is measured to be 115 centigrade, when condensation first occurs. What is the Initial Temperature? I know that the temperature and pressure at point two (saturated vapor) can be found in a standard...
  40. W

    What the escape rate of water vapor into space?

    I understand that some water vapor escapes into space but what's the amount say per year?
  41. I

    Water vapor and air - questions

    Hi.. I'm a pilot and I'm trying to get a better grasp on meteorology. I'm wondering how exactly water vapor is contained in air. I understand it's mostly governed by the temperature of the air but does the temperature of the water affect that? Why is it dependent on the temperature of the air...
  42. K

    Partial Pressures of an Ideal Gas Mixture Containing Water Vapor

    Homework Statement A gas mixture of 0.13 mol NH3, 1.27 mol N2, and 0.025 mol H2O vapor is contained at a total pressure of 830 mm Hg and 323 K. Calculate the following: (a) Mole fraction of each component. (b) Partial pressure of each component in mm Hg. (c) Total volume of mixture in m3...
  43. M

    Evaporation of a solid in water vapor.

    Can a solid, no matter how small, even a single cell, be evaporated with water vapor from a pool of water?
  44. J

    Entropy of liquid water and water vapor

    Homework Statement 1- Use the thermodynamic table to establish an equation giving the molar entropy of liquid water as a function of temperature. Do the same for water vapor. 2- Use these equations to calculate the entropy of vaporization and the enthalpy of vaporization. 3- From the...
  45. B

    Water + Water Vapor - Can I use ideal gas law?

    Homework Statement Sealed container which is used to heat 200 kg water is initially at 25 degrees C. Since the container is sealed, the water remains in saturated state while its temperature and pressure increases. The remaining volume of the container is filled with water vapor at the same...
  46. G

    Calculating maximum amount of water vapor per unit volume

    Homework Statement Compute the maximum amount of water vapor per unit volume that air can hold at the surface, where Ts = 288 K, and at a height of 10 km where T = 220 K. Express your answers in kg m-3. Homework Equations e_{s}=Ae^{\beta T} e=\rho _{v}R_{v}T The Attempt at a...
  47. M

    Water vapor / energy question

    The following is something that puzzles me a bit, and I'd appreciate some insight in the matter. Thank You :) Given the following: A shallow pan with a smaller diameter beaker sitting in it's center Both the pan and the beaker contain distilled water The level of the water in the beaker...
  48. R

    Precipitable Water Vapor calculation

    Hi there, I am trying to calculate the precipitable water vapor, or column water vapor amount, from a given volume mixing ratio at a particular pressure. What is the procedure to do this? I understand you can convert volume mixing ratio to mass mixing ratio, by multiplying by the ratio of...
  49. B

    Calculate Mass of Water Vapor in NaHCO3 + HCl Reaction

    Homework Statement Find the mass of water vapor. this is the reaction: NaHCO3+HCl-->NaCl+CO2+H2O V=39.5 L P=18.65 mm Hg T=294 K n=30.5 mol H20 (g) pressure of room= 29.68 inHg=753.87mm Hg Homework Equations The Attempt at a Solution Would i have to use this equation...
  50. G

    Percent water vapor - greenhouse gas

    I'm have armchair interest in greenhouse gases. One of the interesting points is the amount of greenhouse effect that CO2 has versus water vapor. I go to this page http://www.climate4you.com/GreenhouseGasses.htm and find that the relative percentage of atmospheric humidity is 45%. I...