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Homework Help: Thermodynamics water/water vapor question

  1. Nov 8, 2009 #1
    I am having problems with a Thermodynamics question:

    I am struggling to work out why the meniscus would move up at all.

    Surely its maximum height is the height of the meniscus at the very beginning when all of the water is liquid?

    Once the water is added, some evaporates as the pressure in the tube is initially 0. Then it would reach an equilibrium of water vapor and liquid water. Wouldn't this cause the meniscus to drop as the volume of water liquid decreases?

    The question then states that the temperature is increased above 647.3K. Surely this would cause the saturation vapor pressure to increase and the meniscus to fall further?

    Any help would be greatly appreciated.

    Many thanks

  2. jcsd
  3. Nov 8, 2009 #2


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    2017 Award

    For a given volume of gas, the gas will exert a higher pressure at higher temperatures. You need to take this fact into account as well as the increased vapor pressure of water at higher temperatures.
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