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Homework Help: Question about Q=mcΔT when doing calorimetry

  1. Nov 7, 2011 #1
    1. The problem statement, all variables and given/known data

    When using the equation Q=mcΔT for the substance being tested is it the mass of the substance or the mass of the substance + mass of water.

    2. Relevant equations

    3. The attempt at a solution

    So when I solve calorimetry problems, I usually find Qwater. Then I set Qsubstance=-Qwater. But then I have to use mcΔT, I'm not sure if it's the mass of the substance or the mass of the substance + mass of the water because I've gotten a few questions wrong and the textbook briefly mentioned the sum of masses but gave no examples. Thanks for your input.
  2. jcsd
  3. Nov 7, 2011 #2
    Re-arrange your equation as follows:

    c = [itex]\frac{Q}{mΔT}[/itex]

    Since 'c' is for the substance, what would 'm' be for?
  4. Nov 8, 2011 #3
    m is for the substance right? Not the sum of the mass of the water and substance.
  5. Nov 8, 2011 #4
    Yes, and you can relate to the definition of specific heat: energy required to raise the temperature of one unit mass of the 'substance' on unit degree.
  6. Nov 8, 2011 #5


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    Staff: Mentor

    Like specific heat of brine :tongue:
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