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Calculating energy needed to melt aluminum cans?

  1. Jan 31, 2013 #1
    1. The problem statement, all variables and given/known data
    You have collected exactly 1500 aluminum cans for recycling, each with a mass of 13.9 g. How much energy is needed to melt them if their initial temperature is 25.5◦C? Assume
    the specific heat, the latent heat and the melting point of aluminum are 899 J/kg ·◦C, 3.97 ×10^5 J/kg and 660.4◦C, respectively.
    Answer in units of J.


    2. Relevant equations
    I'm pretty sure that the equations used are Q=mcΔT, and after getting that, using the Q=mL formula..


    3. The attempt at a solution
    So, for the Q=mcΔT part, I put; Q= (13.9)(899 J/kg◦C)(634.9)+(13.9)(397000 J/kg) which is 1.34*10^7. I put it in my homework online and it said it was incorrect. I later did Q=(13.9)(899)(634.9) which was 7933773.89 and then put it into Q=ml.. 7933773.89=13.9(397000) and it calculated to be 7933773.89=5518300. Do I subtract, divide? I have a feeling I'm doing it wrong. I don't know what to do after this step, my teacher was explaining it at the end of class really fast and I didn't get to finish writing down the notes.
     
  2. jcsd
  3. Jan 31, 2013 #2

    tms

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    How many cans are you trying to melt?
     
  4. Jan 31, 2013 #3
    Exactly 1500 Aluminum cans.
     
  5. Jan 31, 2013 #4

    tms

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    And how many cans did you use in your calculation?
     
  6. Jan 31, 2013 #5
    Well, 1500.
     
  7. Jan 31, 2013 #6

    tms

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    Check again. Also check your units.
     
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