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Urgent help need.Please ! Heat question

  1. Apr 18, 2007 #1
    Urgent help need.Please !!!!!! Heat question

    1. During an all-night cram session, a student heats up a one-half liter (0.50 10-3 m3) glass (Pyrex) beaker of cold coffee. Initially, the temperature is 20°C, and the beaker is filled to the brim. A short time later when the student returns, the temperature has risen to 92°C. The coefficient of volume expansion of coffee is the same as that of water. How much coffee (in cubic meters) has spilled out of the beaker?



    Coefficient of volume expansion for water is 207 x 10^-6

    I used the equation

    delta V = beta x volume x delta T

    = 207x10^-6 X 0.5x10^-3 X 72

    = 7.452 X 10 ^-6


    But the answer is wrong
     
  2. jcsd
  3. Apr 18, 2007 #2
    what are the units of beta?
     
  4. Apr 18, 2007 #3

    Dick

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    That looks fine to me. What's the answer supposed to be?
     
  5. Apr 18, 2007 #4
    The unit is 1/ degrees celcius.





    i dont know the right answer
     
  6. Apr 18, 2007 #5

    Dick

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    Ok. Are you sure that isn't a coefficient of linear expansion? Sorry, but I can't check for you right now.
     
  7. Apr 18, 2007 #6
    water has no coefficient of linera expansion
     
  8. Apr 18, 2007 #7
    that seems wrong, volume or sg changes by a couple of percent over the range mentioned.
     
    Last edited: Apr 18, 2007
  9. Apr 18, 2007 #8
    my bad it asks to be reported in cubic meters. I get the same answer.
     
    Last edited: Apr 18, 2007
  10. Apr 18, 2007 #9

    hage567

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    Where did you get your value for beta from?
     
  11. Apr 18, 2007 #10
    Hage, I looked it up as well, was 0.00021 on Wiki iirc.
     
  12. Apr 18, 2007 #11

    Dick

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    I finally got out from under internet blockages as well, and I notice that that is correct at 20 degrees, but it's over 3 times larger at 90 degrees. Perhaps, choosing an intermediate temperature would give you a better approximation.
     
  13. Apr 18, 2007 #12

    hage567

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    Yes, I found that too. I was wondering if the value was stated in the text somewhere or if the OP looked it up.
     
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