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Why does water defy appear to defy gravity when evaporating?

  1. Dec 10, 2008 #1
    why does water defy appear to defy gravity when evaporating??

    1. The problem statement, all variables and given/known data
    I am not the most astute at physics so please forgive my shortcomings, but i was wondering how it is that a saucepan of water cannot levitate, yet if left alone over time the water will levitate for a period before gravity pulls it down again.

    As water is much heavier than air, i am puzzled as to the mechanics of evaporation and how at first glance, evaporation appears to defy newtonian laws.




    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Dec 10, 2008 #2

    mgb_phys

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    Re: why does water defy appear to defy gravity when evaporating??

    So does getting out of bed in the morning.
    All gravity says is that there is a force downwards, it doesn't say that you can't produce a bigger force to overcome it.
    When you boil water you add kinetic energy and the water molecules move around more - eventually they have enough energy to break away form their neighbours and escape as a gas.
     
  4. Dec 10, 2008 #3
    Re: why does water defy appear to defy gravity when evaporating??


    Yes, but evaporation occurs way below boiling point, which should keep the water as a liquid. A glass of water will evaporate at room temperature, so why does the water not remain in the glass as a liquid??
     
  5. Dec 10, 2008 #4

    Janus

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    Re: why does water defy appear to defy gravity when evaporating??

    The measure of temperature is a measure of the average kinetic energy of the molecules involved. Individual molecules can have kinetic energies greater or less than this. Even at room temp, some molecules will have enough kinetic energy to escape as a gas and cause evaporation.
     
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