Supercool: Water Doesn't Have to Freeze Until -48 C (-55 F)

[n2doc]

ScienceDaily (Nov. 23, 2011) — We drink water, bathe in it and we are made mostly of water, yet the common substance poses major mysteries. Now, University of Utah chemists may have solved one enigma by showing how cold water can get before it absolutely must freeze: 48 degrees below zero Celsius (minus 55 Fahrenheit).


That's 48 degrees Celsius (87 degrees Fahrenheit) colder than what most people consider the freezing point of water, namely, 0 C (32 F).

Supercooled liquid water must become ice at minus 48 C (minus 55 F) not just because of the extreme cold, but because the molecular structure of water changes physically to form tetrahedron shapes, with each water molecule loosely bonded to four others, according to the new study by chemists Valeria Molinero and Emily Moore.

The findings suggest this structural change from liquid to "intermediate ice" explains the mystery of "what determines the temperature at which water is going to freeze," says Molinero, an assistant professor at the University of Utah and senior author of the study, published in the Nov. 24 issue of the journal Nature.


http://www.sciencedaily.com/releases/2011/11/111123133123.htm

[Denninmi]

1. Supercooled water happens in real life.

Not that hard to do, actually, I've had bottled water do that in the freezer -- the pressure its under prevents it from freezing, and then, as soon as you open the top, poof, it freezes up. Kind of fun to watch it happen.

[catbyte]

2. That happened to a Faygo Diet Ginger Ale just last night, LOL

I forgot about it and when I opened it, fizzzzzzzzzzzz! Thunk. Frozen. Flat.

:)

Diane
Anishinabe in MI

[Odin2005]

5. That happened to a bottle of Fiji water I had!

The water froze so fast that it did not form crystals, it was an amorphous plastic-like thing.

[VWolf]

3. The way I learned it (about 20 years ago) was that

homogeneous nucleation of ice doesn't begin until around -40C. Between 0C and -40C, the water is supercooled and relatively unstable to freezing. A number of factors (impurities, etc) would lead to heterogeneous nucleation in this temperature regime.

That said, once water is frozen, it will stay that way until the temperature rises ABOVE 0C. So I like to think of 0C as the melting point of water, not the freezing point.

The -48C thing is what's new, and it's pretty cool (pun intended).

[Gregorian]

4. I'll always remember this story from my high school chem teacher

He came to class all excited one morning. When he went out to his car, it was wet. But the instant he touched it to open the door, the water immediately went through the phase change from water to ice. Evidently the water was supercooled, and the mere act of touching part of it set off the change.

Water is an amazing substance.