1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Fusion related problem (help please, chem final is tomorrow!)

  1. Jun 13, 2005 #1
    ok my final exam for chem is tomorrow and i need help badly on this practice problem! here it is:

    3. When 9.250 kJ of heat is added to 20.0 g of ice at 0.0 degrees Celcius, what is the final temperature of the water? The heat of fusion for water is 335 J/g.

    I don't know how on earth to connect the fact that i was given the "fusion" (fusion - huh???) of water with the other stuff. I know that q=(c)(m)(delta T) but how do i connect all this together?

    this is what i did (and failed misrebaly):

    q=(c)(m)(delta T); m=20.0 g; T initial=0.0 degrees Celcius; q=9.250 kJ (which is 9250 J if i wanted to work with the same units)

    so:

    9250 J=[4.184J/(g*degree Celcius)](20.0 g)(T final - 0.0 deg. Celcius)
    9250 J=(83.68)(T final)
    111 deg. Celcius=T final


    WRONG!!

    HELP PLEASE! :cry: :uhh: :confused:
     
  2. jcsd
  3. Jun 13, 2005 #2

    OlderDan

    User Avatar
    Science Advisor
    Homework Helper

    Heat of fusion, often called "latent heat of fusion" is the amount of heat needed to melt ice without changing its temperature, or the amount of heat you need to remove from water at freezing temperature to change it ("fuse" it) into ice.
     
  4. Jun 13, 2005 #3
    Oh, hey thanks a lot.

    But how do I relate that bit of information to the problem?
     
  5. Jun 13, 2005 #4
    where is everybody?
     
  6. Jun 14, 2005 #5

    OlderDan

    User Avatar
    Science Advisor
    Homework Helper

    You figure out how much heat is needed just to melt the ice you started with before you calculate the temperature change of the water resulting from the rest of the heat added.
     
  7. Jun 14, 2005 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    1. Determine how much of the heat is required to melt the ice- that is the heat of fusion times the mass of the ice.
    2. Subtract that from the original 9.25 J to see how much heat is left to raise the temperature of the water.
    3. Calculate how many degrees that much heat will raise the water- that is the number of degrees one J of heat will raise 1 g of water times the number of J left times the mass of water.
     
  8. Jun 14, 2005 #7
    ans

    3. When 9.250 kJ of heat is added to 20.0 g of ice at 0.0 degrees Celcius, what is the final temperature of the water? The heat of fusion for water is 335 J/g.

    9.250kJ = 9250J
    energy required to melt ice = 335 * 20 = 6700J
    energy left after ice has melted = 9250 - 6700 = 2550J

    taking specific heat capacity of water to be 4.2 J g^-1 degreeC^-1

    therefore heat capacity for 20g of water is 84 J C^-1

    increase in temperature = 2550 / 84 = 30.6 degree C

    therefore final temperature = 0.0(initial temp) + 30.6 = 30.6 degree C
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Fusion related problem (help please, chem final is tomorrow!)
  1. Help finals tomorrow (Replies: 3)

Loading...