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First order phase transition (van der waals gas)

  1. Apr 20, 2010 #1
    I am looking at some of the notes but don't quite understand this.

    What are the physical explanation of the graphs (Fig 4(a) and 4(b)) on Page 4 ?
    http://www.pma.caltech.edu/~mcc/Ph127/b/Lecture3.pdf" [Broken]

    Why [tex]V_{g}[/tex] decreases with temperature but [tex]V_{l}[/tex] increases with temperature?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 22, 2010 #2
    Anyone who can help? please...
  4. Apr 23, 2010 #3


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    Look at the Maxwell construction: When the temperature rises, the two loops in the theoretical p-V curve become less and less pronounced until they disappear at the critical point. At the critical point Vg and Vl coalesce, hence the distance of Vg and Vl has to decrease with temperature.
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