Re: vapor

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

> -----Original Message-----
> From: Joseph E Sabol [mailto:jsabol@NMU.EDU]
> Sent: Monday, May 20, 2002 6:11 PM
>
> [snip]
>
> > Let's consider *any* clear day with no puddles on the ground.
> >  What would
> > you call the gaseous phase of water that is present in the atmosphere?
>
> I would call it gaseous phase water, aka, H2O(g).  But I
> might slip up and
> say water vapor, too.
>
> [snip]
>
> I think the "experts" should call it water gas phase.
>
> [snip]
>
> For substances that are usually a gas at RT conditions, e.g.,
> CH4, "gas" is
> probably the best/only term.  However, for substances that
> can have both
> gas and condensed phases, perhaps "vapor" is better (i.e.,
> CH4 vapor on
> Jupiter.)

So is "vapor" better or "gas" better?  It seems to me that "vapor" is the
accepted term.  If you feel it should not be, please explain why.

Personally, I blame phase diagrams for part of the problem.  I think they
confuse students.  Students don't realize what the P refers to (it is
pressure of the substance at equilibrium, no?) and end up thinking that the
gas phase of water cannot exist below 100C or that gas and liquid water
cannot coexist except in rare circumstances.

____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301