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-----Original Message-----
From: Joseph E Sabol [mailto:jsabol@NMU.EDU]
Sent: Monday, May 20, 2002 2:02 PM
To: PHYS-L@lists.nau.edu
Subject: vapor
[snip]
So, in my opinion, a "gas" is w/o any condensed phase present
and a "vapor"
is a gas in equilibrium with its liquid or solid or both.
For systems not at equilibrium, I suppose you could say a
vapor is present,
but once the pressure = the equilibrium vapor pressure, the
system is at
equilibrium. The example that comes to mind is, on a hot
Summer day, the
puddle of water on the road, after the rain storm: Clearly, the vapor
pressure of water is less that the equilibrium v.p. at that T
- its not
raining anymore. But the puddle is getting smaller, i.e., H2O(l) -->
H2O(g). The problem is describing the equilibrium situation
at the puddle
surface from T and P not at the surface and essentially an
open system.