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Homework Help: Specific heat capacity and latent heat of fusion

  1. Mar 17, 2007 #1
    help! need help here because my answers are different from the answer on the book. just wanted to make sure that i am right. these are the problems:

    1. How much heat is needed tor aise the temperature by 10 deg celsius of 5 kg og a substance of specific heat capacity 300J/kg deg celsius? what is the thermal capacity of the substance?

    - i got the answer for the specific heat capacity but for thermal capacity my answer is 1500 J/deg celsius and the book's answer is 15000 J/deg celsius.

    2. If a freezer cools 200 g of water from 20 deg celsius to its freezing point in 10 minutes, how much heat is removed per minute from the water?( this is under specific latent heat of fusion but i think i solved it using specific heat capacity)

    - my answer is 1680 J/min but the book's answer is 1700 J/min.

    please help me. thanks
  2. jcsd
  3. Mar 17, 2007 #2
    Your book rounded to 2 sig figs (10 minutes, 20 degrees) for number 2
  4. Mar 17, 2007 #3


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    For question 1, You say the answers are in J/oC, but I don't understand that since you are using the 10oC in your calculation. If you multiply your 1500 J/oC by 10oC, you get 15000 J. Does the book really say 15000 J/oC as the answer?
  5. Mar 18, 2007 #4
    thank you for your reply. I am so sorry, made a mistake there. I have solved the energy needed which is 15000J but the heat capacity that i got is different from the answer in the book. my answer is 1500 J/deg celsius and in the book is 15000 J/deg celsius.
  6. Mar 18, 2007 #5

    thanks! meaning my answer is right and i just have to round it off to the nearest hundred/ simply follow the rules in significant figures. thanks again!