[chris (OP)]

Someone told me today that they left their dog's bowl out overnight; in the morning the water it contained was extremely cold, but still liquid. Nonetheless, as soon as they touched the water it froze.

How did that happen?

Chris

[Geezer]

It's possible to cool water well below its freezing point without it actually crystallizing. It becomes a super cooled liquid. The purer the water is, the more likely the effect.

If you introduce a small seed crystal to the water, it crystallizes rapidly. It's possible that he initiated the process by touching the surface of the water, or introduced an impurity thatpromoted crystal growth.

It should be possible to reproduce the effect with some distilled water and a freezer or a freezing solution (ice and salt).

[lightarrow]

Yes, certainly, but he asked why  []

[The Scientist]

It has reached saturation point so when it is being touched, the kinetic energy is disturbed and the water molecules will suddenly freeze into solid ice.