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Question about triple point

  1. Feb 24, 2010 #1
    i know triple point is the temp. that water's(here use water as example)

    solid、liquid、gas state can be existent .

    http://www.youtube.com/watch?v=BLRqpJN9zeA


    the video is amazing

    and so, how can he change water's state?

    (solid、liquid、gas state can be existent at the same time, but how can we change its state?)

    lastly, how can we produce triple point?

    i'm sorry about i just have F.3 standard now

    so please explain it in a simplier way.

    thank you so much!
     
  2. jcsd
  3. Feb 24, 2010 #2

    Andy Resnick

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    The triple point is interesting because it is the basis of a standard thermodynamic state- that is, if you have some water at the triple point, and I also have some water at the triple point, we know that our samples must be at the same temperature and pressure-something that cannot be said for any other thermodynamic state without comparing thermometers and barometers. So I can use a triple-point cell to calibrate a thermometer and barometer.
     
  4. Feb 24, 2010 #3

    Gokul43201

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    The triple point is produced by carefully adjusting the temperature and pressure in the container to a very specific value.

    By changing the temperature or pressure, the state of the system (water, alcohol, etc.) can be changed.
     
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