Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Specific Heat of water

  1. Oct 19, 2006 #1
    Does anyone know how to do this? :uhh:

    I've tried to figure it out but it aint working =/
    its for a test i gotta turn in now. argh.

    The specific heat capacity of water is high, 4.184 J/gºC. The presence of impurities in a sample of water lowers its specific heat capacity. What is the specific heat capacity of the sample if 100 grams of it now requires 200 Joules of heat for a 1.8ºC temperature increase? What are the effects of the low specific heat capacity of the sample of water?

    Its okay if anything, i just need to pass this test, anything would help about now. Thank you guys very much.
  2. jcsd
  3. Jul 25, 2007 #2
    Im probably waay to late to help you out. :frown:Im taking that test now. the answer to the specific heat equation is 0.9 J/g C...but I need the second part of that question :confused:
  4. Jul 25, 2007 #3


    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    The first part is nothing more than plugging in the given values. For the second part, understand what specific heat capacity means. A given material can take in a corresponding amount of heat; look again at the units, and use the idea that temperature can be a variable. If x joules of heat are put into a material but temperature changes very little, then heat capacity is a value. If x joules of heat are taken into a material but change of temperature is large, then value of heat capacity is less.

    The units for specific heat capacity is (Joules/(gram.degreesC));
    Note that "grams" and "degreesC" are in denominator position.
  5. Jul 25, 2007 #4
    You can just plug the information into this equation then solve for the unknown.

    Heat = Mass x Specific heat capacity x temperature change

    I did not get .9 J/g C when I worked the problem, but maybe I'm doing it incorrectly, its been awhile.

    For the second question, specific heat is joules over grams times temperature change. So if the specific heat of water is 4.18J/g C, it is saying that it takes 4.18 joules to heat 1 gram of water 1 degree Celsius. If you have a lower specific heat then that is telling you what?

    Another example, the specific heat of copper is .385J/g C. So if you have a copper pan on the stove, which heats up faster, then pan or the water in the pan? Thinking about this should give you a suitable answer to the second part of the question.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook