Re: The importance of being pedant

[William Beaty <billb@ESKIMO.COM>]

On Sat, 24 Jul 1999, Robert A Cohen wrote:

> For example, I've always used vapor to describe an evaporated liquid.
> The vapor, having evaporated from the liquid, is a gas and the vapor
> can coexist with the liquid.  On the other hand, I don't consider a gas
> like atmospheric nitrogen a vapor because it isn't in equilibrium with
> a liquid phase.

Thinking out loud for a moment:  suppose I have a large bottle of dry air
at STP, and I inject a tiny droplet of water.  The water evaporates.
There is no liquid present, and the evaporated water is not in equilibrium
with liquid water.  Is the water now a vapor, or is it a gas?  If it's a
"vapor", how are its molecules different from, say, a trace amount of
hydrogen gas injected into the same air?


Suppose I have an open styrofoam tray of liquid nitrogen sitting on the
table.  We all know that LN2 can be hazardous because it aquires LOX from
the atmosphere.  Oxygen is a gas in the environment, but at the surface of
the LN2 in the tray, oxygen is condensing.  Does this mean that the air
at a fraction of a mm above the LN2 contains "oxygen vapor", but the
air a few cm above the surface contains "oxygen gas?"   As the oxygen in
the atmosphere approaches the cold LN2 surface, does it change from "gas"
to "vapor?"




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