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Homework Help: Liquid freeze => give heat?

  1. Dec 28, 2006 #1
    1. The problem statement, all variables and given/known data
    When a liquid freezes, it gives out heat. Where does this heat come from?

    2. Relevant equations

    3. The attempt at a solution
    Does this only apply to water or other chemical substances as well.

    The heat comes from the strong bonding when as a liquid. But now this kind of potential energy stored in the bonds is released into kinetic energy hence heat outflow. This explanation is only for water as the liquid state has stronger bonding hence higher potential energy in the liquid bonds. But what about other chemical substances?
  2. jcsd
  3. Dec 28, 2006 #2


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    Last edited by a moderator: May 2, 2017
  4. Dec 28, 2006 #3
    At a molecular level, why is heat released when liquid is turned into solid? People usually explain it in terms of when solid is turned into liquid, heat is added. I want to know the other way around. Is it because there use to be a bit of kinetic energy in the molecules when in liquid state but after it has changed into a solid, this kinetic energy is lost. It can't disappear and we measure a decrease in temperture of the substance so heat must be released. We can also measure an increase in the temperture of the surrounding environment if the temperture is at or colder than the melting pt of the substance?
    Last edited: Dec 28, 2006
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