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

Thermodynamics regarding ideal gases and the absolute zero.

  1. Oct 25, 2010 #1
    Hello colleagues, I have a seminar that i need to turn in a weeks day from now.
    My professor listed the following questions, guidelines that I should lean on:

    1) Is it possible to achieve a temperature bellow absolute zero (-273,15)

    2) An ideal gas contracts linearly when decreasing temperature towards absolute zero, why?

    3)A real gas doesnt contract linearly,why? it has more variables than the ideal gas, but this is not the complete answer.

    4)Why is the absolute zero temperature the common ending point for both(real and ideal)

    colleagues, i think the answer here lies in the specter that lies deeper than what most engineers abide by. We must go deeper than continuum, i think all the answers can be interpreted through the molecular level. And now im asking you if you know any good links that could help me with my seminar. Also if you have any helpful information feel free to share.
     
  2. jcsd
  3. Oct 26, 2010 #2

    alxm

    User Avatar
    Science Advisor

    Nope, all these questions are answerable without making use of statistical thermodynamics (i.e. the 'molecular level').
     
  4. Oct 26, 2010 #3
    please post something constructive, a link maybe? or maybe care to elaborate on your statement.
     
  5. Oct 29, 2010 #4
    Aside from the lack of evidence of sub-zero K (Kelvin) temperatures,

    I think the OP should look to the canonical distribution for some information. There you could "experiment" with what would happen to the energy levels if you let them approach negative, or even zero.

    You could also look to E=kT as well. Where E is total energy, k is the boltzmann constant, and T is in Kelvin, what would happen if T < 0? Can we have a E less than zero? Can we have an E = 0?

    For the second question, look to the Ideal-Gas Law.. figure it out yourself: pV=nRT

    For number three, that's a fun one. I can think of a number of reasons why, depending on what level of Physics you are familiar with. I'd reckon that mentioning that interactions between particles at lower temperatures become non-negligible and so transitions between states (i.e. gas to liquid to solid) becomes important. Ideal-gas law doesn't allow for this.

    4. I suggested it above I think.
     
  6. Oct 31, 2010 #5
    It is impossible to achieve absolute zero temp. Because according to the Kelvin's observations, the volume & pressure of a gas becomes zero at -273.15. i.e
    temperature is inversely proportional to volume & pressure. That's why he started measuring temperature from this point.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook