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How to find the specific heat capacity of a mixture?

  1. Dec 14, 2015 #1
    1. The problem statement, all variables and given/known data
    For my physics IA, I am finding the specific heat capacity of water-solute mixtures and finding how the specific heat differs from that of just water alone. I have the mass of the mixture, for example baking soda and water was 914.75g and changed 175.8 degrees Fahrenheit in 9.5 minutes. I just need to know the specific heat capacity along with Q in the equation.

    2. Relevant equations
    3. The attempt at a solution
    I can't find the solution because I am missing two variables: Q and C. If there's any way to find either solution, please let me know. Thank you!
  2. jcsd
  3. Dec 14, 2015 #2
    Do you know the imposed heating rate?
  4. Dec 14, 2015 #3
    I'm not 100% sure what you mean by this. Can you give me an example please? Thanks for the help!
  5. Dec 14, 2015 #4
    Your'e using a heater, right? What is the power input of the heater?
  6. Dec 14, 2015 #5
    I was using a gas stovetop set on high to heat it from solid form until it boiled.
  7. Dec 14, 2015 #6
    Too bad. Game over. You need to know the rate at which you are adding heat. You might be able to do this by first measuring how fast the water heats up when the stove is at full blast with pure water in the pot, and then use this to scale the heat capacity in your solutions. But, some of the heat also goes into the pot.

  8. Dec 14, 2015 #7
    So if I were to redo the trial with an electric stove that puts out 2500 watts, would it be easier to find the specific heat?
  9. Dec 14, 2015 #8
    Yes, providing you could make sure that all the heat goes into the water and pot and none escapes to the room and stove. The difference you are trying to detect is very tiny, and the slightest error in the heat flow to the water can lead to very inaccurate results. This is really a very sensitive measurement that really needs to be made under carefully controlled laboratory type conditions.

  10. Dec 14, 2015 #9


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    BTW, the purpose of your experiments is to determine C, which is the specific heat capacity.
  11. Dec 14, 2015 #10
    Yeah but I'm having trouble finding C because of my lack of Q. Do you know whether or not I could use the wattage of an electric burner as Q if I decided use an electric stove that puts out 2500W?
  12. Dec 14, 2015 #11


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    Subject to what Chet said in Post #8. You might have to arrange an experimental control, whereby you use the electric stove to heat up a known quantity of pure water.
    You can measure the temperature change of the water and compare your calculation of the heat output by the stove with the amount of heat absorbed by the pure water.
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