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Supercooled Water

December 7, 2011

On a molecular level, water doesn’t have to become ice until minus-55 degrees Fahrenheit.

Transcript

BOB HIRSHON (host):

Water’s drop-dead freezing point. I’m Bob Hirshon and this is Science Update.

We all know water freezes at 32 degrees Fahrenheit, or zero Celsius.  But that’s not the whole story.  University of Utah chemist Valeria Molinero and her colleagues found that water doesn’t have to fully freeze until minus-55 Fahrenheit, or minus-48 Celsius.  Above that temperature, solid ice is really a mix of ice crystals and liquid water; below it, virtually all the molecules crystallize.

VALERIA MOLINERO (University of Utah):

Not only because the temperature is lower, but we show that irrespective of the temperature, this is controlled by a change in the structure in the liquid.

HIRSHON:

She explains that as the temperature drops, the structure of liquid water molecules gets closer and closer to that of ice crystals. The closer it gets, the faster true crystals can form.  The findings may help explain how super-cooled water vapor behaves in the upper atmosphere, which indirectly affects global climate.  I’m Bob Hirshon for AAAS, the Science Society.