Opening Soda Pop and Ice Formation

name         Christian
status       student
grade        6-8
location     NY

Question -   When opening a bottle of pop kept at a temperature 
of 35 degrees F. ice forms. Does the release of carbonation have 
anything to do with the ice forming?
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Christian,

Look at a "phase diagram of water". (I did a web-search and this site came up:

http://www.science.uwaterloo.ca/~cchieh/cact/c123/phasesdgm.html

I will refer to the pahse diagram of water here).

If you look at the graph where it says "1atm" on the y-axis and 
imagine a straight, flat line from that point, you will note that 
you will cross from solid to liquid (in the diagram from green to 
blue) at the point where the temperature is zero deg-C (point #4 on the graph).

Now, imagine a can of soda that is at zero deg C -- but which is 
under pressure (from all the carbon dioxide in the can). This means 
that you would have to go up the zero deg-C line to higher pressures 
(to somewhere near point #5 on the graph). Notice that this is the 
liquid state (blue area). Now suppose the pressure is released - as 
when opening the can, the pressure will drop and you will move down 
this line and go to the solid state (point #3 on the graph).

Thus, because the solid-liquid line of water is tilted backward (has 
a negative slope), water tends to be a liquid at high pressures and 
a solid a low pressures for temperatures below zero deg-C.

Greg (Roberto Gregorius)
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