Re: [Phys-l] Thermodynamics, P vs. T plot

[chuck britton <cvbritton@mac.com>]

If the specific volumes of the two phases were equal, then the phase 
boundary would be vertical.
(Clausius Clapyron equ.)

At 6:02 PM -0700 11/23/10, John Denker wrote:
> On 11/23/2010 05:42 PM, Peter Schoch wrote:
> >  The question arose asking if anything has a transition line that is
> >  vertical or nearly vertical. I admitted to never having seen one, and
> >  did not think it was possible -- but I am unsure of that last point.
> >
> >  What would a vertical, or nearly vertical, transition line have as a
> >  physical significance?  Any insights would be most welcome!
>
> The physical significance is associated with the fact that
> water expands when it freezes, which is associated with the
> funky crystal structure of ice.
>
> If you had something what was very slightly less funky, the
> phase boundary would be vertical.  This would not cause even
> the slightest difficulties, theoretical or otherwise.
>
> FWIW the boundary between ice VII and ice VIII is very nearly
> vertical on the P versus T plot (aka horizontal on the T
> versus P plot)
>   http://www.benbest.com/cryonics/lessons.html
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