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Kinetic energy of water vs ice

  1. Mar 20, 2016 #1

    TT0

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    1. The problem statement, all variables and given/known data
    The average kinetic energy of water at 0 °C is __________ the average kinetic energy of ice at 0 °C.

    2. Relevant equations


    3. The attempt at a solution
    I said that it is greater than because when ice melts, energy is added to break the potential energy (bonds). I also know that average kinetic energy is directly linked to temperature so if they are at the same temperature, the average kinetic energy should be the same. The thing that is confusing me is that when the latent heat of fusion is applied to the ice, it breaks the bonds so it releases the potential energy so shouldn't the kinetic energy of water be higher than ice?

    Cheers!
     
  2. jcsd
  3. Mar 20, 2016 #2

    haruspex

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    Isn't that adding potential energy?

    When a thermometer measures temperature, what is it actually responding to?
     
  4. Mar 20, 2016 #3

    TT0

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    It is responding to the kinetic energy, but when the latent heat of fusion is applied, doesn't it break the bonds so therefore the potential energy would decrease? I am pretty sure this is wrong but I don't understand why. For example I think water has a lot of potential energy in its bonds and this potential energy is lost when it turns into gas because the bonds are broken. The potential energy is transferred into something which I am not sure of. Please help, thanks!
     
  5. Mar 20, 2016 #4

    haruspex

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    You have the changes in PE backwards. To break a bond you have to inject energy, just as you have to supply energy to send a rocket up, overcoming the attraction of the earth. The PE increases.
     
  6. Mar 21, 2016 #5

    TT0

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    I see thanks!
     
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