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Homework Help: Water Temperature mixing together!

  1. Apr 9, 2007 #1
    1. The problem statement, all variables and given/known data
    When 1 kg of water at 100 C is mixed with 10 Kg of water at 0C, the equilibrium temperature will be:

    a) exactly 0 C
    b) Exactly 50 C
    C) Exactly 100 C
    d) slightly above 0 C

    I think that the answer is D) sligtly above 0 C, but i don't know why. I'm not sure what formula to use, and i've been lookking all over the web and my text book.
  2. jcsd
  3. Apr 9, 2007 #2
    When you add 1 kg of water in the liquid phase at 100 C, you can find the heat given out by it when its brought down to T c. That is equal to the heat gained by the 10 kg of water at 0c to come to Tc. Solve for T (final temperature).
  4. Apr 9, 2007 #3
    so am i sopposed to use the Q= mc (Change in temperature) formula

    so like 1 * 4186 * 100
    Q = 418600

    And then 418600 = 10 *4186 *?
    = 41860 * t
    418600/41860 = t
    t = 10

    So it's slightly over 0 C ???
  5. Apr 9, 2007 #4
    yea, intuitively you can see this is a weighted average kind of problem,
    10 parts at 0, 1 part at 100, so ave for 11=9.09 degrees. Now if the water was ice, different animal as latent heats need to be included.
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