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Heat of transformation

  1. Nov 28, 2011 #1
    What happens to the heat required in heat of transformation?

    It doesn't actually raise the temperature of the substance does it?

    IE if I have ice at 0*C and I input the exact energy required to melt it, it's still 0*C?
  2. jcsd
  3. Nov 28, 2011 #2


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    To my knowledge the temperature stays the same while the material undergoes a phase change.
  4. Nov 28, 2011 #3
    It goes into the lattice.

    Temperature is a statistic of microscopic particles, it doesn't mean energy.
  5. Nov 28, 2011 #4
    I agree that temperature isn't energy, but I'm talking about the energy required for the phase-change. Seeing that the addition of energy does imply a change in temperature until the melting point in which it goes into the required heat of transformation, I wondered where it "actually" went.

    But I think I understand your answer, energy will raise the temperature until a certain point, but additional energy is then required to break the molecular lattice. Correct?
  6. Nov 28, 2011 #5
    Ye correct.
  7. Nov 28, 2011 #6
    And the same energy is stored as potential energy until the object freezes again and reforms the lattice, releasing that energy as heat again?

    Thanks, this will let me do problems like this more confidently.
  8. Nov 28, 2011 #7
    For example (this is a homework problem but it is merely to demonstrate)

    Fifty grams of ice at 0°C is placed in a thermos bottle containing one hundred grams of water at 6°C. How many grams of ice will melt? The heat of fusion of water is 333 kJ/kg and the specific heat is 4190 J/kg

    After all of that happens, equilibrium pressure is still just 0*, because all the energy the *6 water went into breaking (a fraction of) the ice's lattice?
  9. Nov 29, 2011 #8
    The energy that goes into turning ice at 0°C into water at 0°C goes into breaking the bonds between the water molecules that form the ice. Temperature is energy. It's the product of the kinetic energy of the particles.
  10. Nov 29, 2011 #9
    yes. the energy added is used only to change its phase from solid to liquid but not used to raise its temperature from 0*C. Same thing goes when you vaporize water at let's say 110*C, you add heat to change its phase from liquid to gas at constant temperature. :)
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