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Specific heat/heat capacity

  1. Apr 9, 2010 #1
    Hello I do not remember the layout for posting and it is not posted because I'm on my mobile phone but I need help finding volume of hot water given the volume and temp of cold water and the temp of hot water.
    I need help finding specific heat given mass and temp
    and I need help finding heat capacity given the specific heat
  2. jcsd
  3. Apr 9, 2010 #2


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    Staff: Mentor

    In each case you need more information to find the answer. For example - you can't calculate heat capacity of water knowing its specific heat. No such thing as "heat capacity of water" - but if you know AMOUNT of water, then you can calculate heat capacity of this specific amount of water. So, first - look at what you are really given.
  4. Apr 9, 2010 #3
    What formula would I use to calculate the heat capacity of,let's say 10 grams of iron?
  5. Apr 9, 2010 #4
    heat capacity doesn't require the knowledge of amount of that substance.

    Heat capacity of a particular sample of a substance is defined as the amount of energy needed to raise the temperature of that sample by 1 degree Celsius.

    Calculate it by using C (heat capacity) = Q (heat given)/ [tex]\delta[/tex] T (temperature change)
    Last edited: Apr 9, 2010
  6. Apr 9, 2010 #5


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    Staff: Mentor

    It depends on the information you are given. OP asked about calculation of heat capacity when specific capacity is known.

    That's correct, but I don't see how it fits the original problem.

  7. Apr 9, 2010 #6
    Specific heat is given then it is very simple. Multiply specific heat by the mass of substance then you'll get the heat capacity for that sample of substance.
  8. Apr 9, 2010 #7
    There is a very little but very important difference between heat capacity and specific heat. To understand it let take one example.

    let's take a rod. I dunno which metal it is made of and what it's mass. But I start heating it and after sometime I found that the temperature is increased by 1 degree Celsius. I calucated that I've given that rod heat (heat is only a mode of energy transfer, actually we give energy) equal to Q. Now I take another rod, do I need exactly Q amount of heat to increase its temperature by 1 degree celsius? I can't be sure bout it and most probably I'll answer no!. That's what heat capacity is.

    Now again I take the same first rod but this time I noted that that rod is made up of Iron and its mass is 1 kg. And now I looked at second rod and found that the rod is also made up of iron and its mass is 2 kg. So As I know that I'd given Q amount of energy for the rod of Iron of 1 kg so I need a double energy for the rod of double mass than first to raise it's temperature by same amount. That is specific heat.

    Now back to question. Since you know how much energy you need to give for that substance of unit mass to increase its temperature by a unit degree so you can calculate the heat capacity by multiplying it with the mass.

    Definition makes it very clear but I've given the explanation because previous poster said that what's the need of that definition.
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