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-   -   Boiling & Freezing water at the same time? (http://www.physicsforums.com/showthread.php?t=78728)

futureteacher Jun11-05 06:14 PM

Boiling & Freezing water at the same time?
 
OK, I'm not a science person. I'm an elementary ed major and we have to take classes in physical science to get the basics.

So, my problem is in plain English!

This month, I have to do a 10 page research paper and presentation on "Boiling water and freezing it at the same time." Now, the only thing I know about water temps is that warm water freezes faster than cold. Can anyone give me any ideas of articles to look for or what to research? I am totally lost!

Thanks

vsage Jun11-05 08:42 PM

You might want to start by looking at a phase diagram for water (see picture 2 and simply look at the colors http://www.lsbu.ac.uk/water/phase.html ). It's pretty clear to see that such a process could only occur below about 0 degrees celsius. Right along the borders of the colored regions in that picture represent points where an equilibrium has been established between two different (or three different) states of matter. I hope I didn't mention something you already knew.

futureteacher Jun11-05 09:52 PM

Thanks! That was very helpful. No, I didn't already know anything about that.

Assume I know nothing. <grin> Anybody else have suggestions...?

Gokul43201 Jun12-05 08:13 AM

The key is in the phase diagram (linked to by vsage) of water. Understand first what a phase diagram is, what information can be got from a P-V diagram and get familiar with a few different phase diagrams, before proceeding.

To have boiling (liquid going to vapor) and freezing (liquid going to solid) at some temperature, you want to have the solid, liquid and vapor phases touch each other in the phase diagram. Clearly, this does not happen at atmospheric pressure (10^5 Pa). You need to get to the "triple point" (about 4.58 torr or 600 Pa and about 273K or 0.01C) to see this phenomenon.

That's one aspect of the problem - the equilibrium thermodynamics. There are other aspects to it too : fluctuations, kinetics, microscopic mechanisms of the phase transitions - hydrogen bonding in the liquid and solid phases, structures of these pahses, colligative effects (on the phase diagram) of adding a solute, etc.

That should start you off and give you a few key words to Google and research.


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