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Compressability of gases

  1. Jun 16, 2006 #1
    Is there a unit to measure the compressability of a gas? What gases are the hardest to compress? The easiest? Any links to a better understanding?
     
  2. jcsd
  3. Jun 16, 2006 #2

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    No.

    Compressibility is measured in reciprocal pressure.

    Ordinarily, I don't get too picky about spelling --- this is a thermodynamic term --- as such, it makes me picky.
     
  4. Jun 16, 2006 #3
    Sure, its called the Bulk Modulus and is defined as:

    [tex]E_v = \frac{dp}{d \rho / \rho} = - \frac{dp}{dV / V}[/tex]

    Basically, it is the negative of the ratio of a change in pressure, p, to the ratio of the change in volume V, to the origional volume, V. (Or instead of volume V, density [itex]\rho[/itex] <but no minus sign>)

    You lost me with this statement.
     
    Last edited: Jun 16, 2006
  5. Jun 16, 2006 #4

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    dV/V ? Unitless. 1/dP ? Reciprocal pressure --- unit(s) of compressibility? Reciprocal pressure.
     
  6. Jun 16, 2006 #5
    The units of the Bulk modulus are pressure, [itex]FL^{-2}[/itex] not the reciprocal. You still have me confused with what your trying to say. :confused:
     
  7. Jun 16, 2006 #6

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    Compressibility is the reciprocal of the bulk modulus. Do the dimensional analysis.
     
  8. Jun 16, 2006 #7
    Oh, my book says the "bulk modulus" but does not say the inverse is called the compressiblity. I just looked it up on wiki.

    Then yes, now you make sense. :wink:

    In that case, take the inverse of everything I have said! (or read your screen upside down)
     
    Last edited: Jun 16, 2006
  9. Jun 16, 2006 #8

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    Thermo for mechs vs. thermo for eggheads vs. thermo for chemists, and all the different approaches taken by authors? Don't let it bug you.
     
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