Will water in vacuum chamber (low pressure chamber(around 0.02 atm)) stop boiling when the remaining air gets saturated? Or if the walls of the chamber are cold enough the water vapor condensates and the boiling continues? Suppose its a fixed vacuum without a vacuum pump continously running.

  • $\begingroup$ Re, "vacuum chamber...remaining air." Maybe you could add some detail to your description of the experiment. E.g., describe the process, and not just the apparatus. If there's air in the container, then it isn't a "vacuum chamber." $\endgroup$ Commented Mar 15, 2021 at 11:23
  • $\begingroup$ A useful video: youtube.com/watch?v=y4BGV7-1lhs $\endgroup$
    – DJohnM
    Commented Mar 15, 2021 at 17:29

1 Answer 1


Will water in vacuum chamber...stop boiling when the remaining air gets saturated?

Air doesn't really get "saturated." Water (or any liquid) evaporates from a surface when the partial pressure of the vapor in contact with the surface is less than the vapor pressure of the substance at the temperature of the surface; and it condenses onto the surface when the partial pressure is higher than the vapor pressure.

Vapor pressure is a characteristic property of any liquid substance, and it depends on temperature: The vapor pressure increases with increasing temperature, which explains why liquids tend to evaporate from hot surfaces and tend to condense onto cold surfaces.

The presense or absense of other gasses (e.g., air) in the chamber doesn't alter the equation.

If you start with a completely evacuuated chamber, and if you let in enough water, and if you do not keep pumping vapor out of the chamber; then the system eventually will reach an equilibrium in which the temperature is the same everywhere, the liquid water is not boiling, and the pressure of the vapor above it is equal to the vapor pressure of water at that equilibrium temperature.

The partial pressure of the vapor in that case will be the same as the total pressure because there won't be any other gas in the mixture.


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