On Wed, 15 Jun 2005 19:35:17 -0500, John Fields wrote:
On Wed, 15 Jun 2005 23:37:49 GMT, Tom MacIntyre

The boiling and freezing points are pressure dependent. Not only that,
a certain amount of heat must be lost or gained (latent heat, I
believe, is the term) before the change of state occurs.

At one atmosphere of pressure, the "latent heat of vaporization" of
water is 540 calories per gram and is the amount of heat required to
change liquid water at 100°C into steam at 100°C. That's used to
great advantage, in reverse, in steam heating systems where steam
which has been generated in a boiler is forced to condense into liquid
water in a remotely located radiator and release that heat into the
environment surrounding the radiator when it (the steam) changes
state.

Well, it takes one calorie per gram to raise liquid water one degree
centigrade - I wonder if, at an ambient pressure of, say, 10^3 Pa, it
still takes 540 calories per gram to transform a gram of liquid water at
0degC to a gram of gaseous steam at 0degC.

I am simply
going by memory of my old Physics classes, and I have no idea what
pressure would be required to allow water to boil at 0 C. I think other
substances have boiled at lower temperatures than that at STP though.

Yes. Liquefied gases, in particular, do that, and I'm anxiously awaiting
Floyd Davidson's response which will nail down the pressure required to
allow water to boil at 0°C.

According to the graph at http://www.lsbu.ac.uk/water/phase.html ,
approx. 10^3 Pa, whatever the hell that means. Obviously, an atmosphere
is up there near the "annoying point", ;-) , between 10^8 and 10^9 Pa.

Hope This Helps! :-)
Rich