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