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Homework Help: How much heat is released from water into ice.

  1. Apr 10, 2012 #1
    1. The problem statement, all variables and given/known data
    How much heat is released when 250 g of water at 10 degrees celcius freezes into ice and cools to -10 degrees celcius?

    2. Relevant equations

    3. The attempt at a solution

    q= (250g)(4186)(283-273)=1.046*10^4 J

    than q=(250g)(2090)(263-283)=-1.045*10^4 J

    when i subtract the two i get 1*10^4

    The answer is -9.86*10^4 what am i doing wrong?
    Last edited: Apr 10, 2012
  2. jcsd
  3. Apr 10, 2012 #2


    User Avatar

    Staff: Mentor

    Three stages:
    1. Cool to freezing point
    2. Freeze
    3. Cool to final temp

    Each stage is governed by a different heat constant.
  4. Apr 10, 2012 #3
    OK this is what I'm doing

    1. cool to freezing point



    MLf=(.250)(3.33*10^5)=8.32*10^4 J

    3.Cool to final temp

    Q= (.250kg)(2090j/kgK)(-283K-273K)=-2.90510*10^5

    so when i sum up Q1+mLf+Q2= -2.177*10^5 J
    Like seriously what am i doing wrong?
  5. Apr 10, 2012 #4
    got it!! i found the mistakes ! thanks! :D
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