Why does water freeze instantly when poured into a bowl?

[katchum]

http://www.collegehumor.com/video:1755006

This may be old but...

How does this work? They need to have a huge warmth transfer coefficient for this to happen? Maybe the water is at 0°C already and a small amount of energy should be taken to get this effect. Is it electromagnetical or is the bowl just cooled with liquid nitrogen or something. The conductivity of water can't be that great?

 

[lpfr]

No, it is just supercooled water. You can cool water well under 0°C but it will not transform in ice if there is not a "seed" of ice or some "good" impurity.

 

[katchum]

What temperature do you recommend for the refrigerator? Half filled or fully filled bottle? Maybe some distillation of the water first?

 

[lpfr]

Sorry, I have never tried. But I think that I will begin with just commercial mineral water as you buy it (before opening the bottle). And begin with a temperature of just -1 or -2 °C. If it doesn't work, I would try distilled water for medical applications (in the unopened original bottle). But as I said, I have never tried myself.