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Homework Help: Melting Ice With Aluminum?

  1. Dec 5, 2007 #1
    Melting Ice With Aluminum??

    1. The problem statement, all variables and given/known data

    How many grams of aluminum at 90 degrees C would have to be dropped into a hole in a block of ice at 0.0 degrees C to melt 10 g of ice?

    2. Relevant equations

    Q = (m)(c)(deltaT)
    c of aluminum = 0.9
    c of ice = 2.1
    c of water = 4.186
    333.7 kJ is needed to get past the ice/water boundary

    3. The attempt at a solution

    I've tried setting up a few different equations, like:
    (.01 kg)(2.1)(+45) + (x kg)(0.9)(-45) = 0
    (.01 kg)(2.1)(+45) + 333.7 + (x kg)(0.9)(-45) = 0
    and a few others I don't have on hand, but I can't seem to get the correct answer. What do I use for delta T? Am I even doing this right at all?

    Thanks for your help.
     
  2. jcsd
  3. Dec 5, 2007 #2

    marcusl

    User Avatar
    Science Advisor
    Gold Member

    No, I think you are missing it. First calculate the heat energy Q needed to melt 10 g of ice. Your latent heat of fusion should read 333.7 kJ/kg. Then solve for the mass of aluminum having this value of Q, using deltaT=90C (since the final temp of the Al is 0C once it's done its job).
     
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