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What will be the change in temperature of the water?

  1. Sep 8, 2009 #1
    1. The problem statement, all variables and given/known data
    A 500.0-g iron bar at 212 C is placed in 2.0 L of water at 24.0 C. What will be the change in temperature of the water ( Assume no heat is lost to the surroundings.)


    2. Relevant equations
    (Mass of substance)(Specific Heat of substance)( Change in Temp)


    3. The attempt at a solution

    I am having alot of trouble with this problem. I don't fully understand how I use that forumula to find the change? I know the answer is 5 C. But I don't understand how. I was wondering if someone could explain how you come about to get this answer using the formulas cause this would be very helpful? Do I have to convert anything or what? So confused.
     
  2. jcsd
  3. Sep 8, 2009 #2

    Ygggdrasil

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    Science Advisor

    From the first law of thermodynamics (conservation of energy), we know that the amount of heat lost by the iron bar will be equal to the amount of heat gained by the water. Assuming the final temperature of the system is the variable T, you can express the change in temperature of the iron bar in terms of T and calculate the amount of heat lost (in terms of T). You can set up a similar expression to calculate the amount of heat gained by the water in terms of T. Then, because you know that the amount of heat lost by the iron equals the amount of heat gained by the water, you can set the two expressions equal and solve for T.
     
  4. Oct 22, 2009 #3
    regarding this problem my dear brother, if we use the way you explained, then we are assuming
    that the change in Temp for water equals the chane in Temp of Iron, the thing that can't
    be proven, because the only thing that can be proven is that the heat(q) lost by the iron is equal to the heat gained by the water..would you please clarify it more for me, because i've
    the same problem but it's a little bit more complicated because neither of lost and gain heat is given and am still stuck for the last few days...really grateful for ur help
     
    Last edited: Oct 22, 2009
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