Kitchen Science: Ice-Nine

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This is a fun little experiment with water that was supercooled to -21C (-6F). The supercooled water is poured into a bowl. It pours out as a liquid and turns to slush, forming ropelike peaks [1:07].

What are the physics behind how water can be supercooled without freezing into a solid? It happens like this; when water is supercooled but remains undisturbed, it does not freeze into a solid unless there is an impurity present (a rough surface, for example) for the cold water to crystallize around (a "nucleation" site). Disturbing supercold water also causes it to crystallize.

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Could you explain to a non-scientist how one supercools water to -21 without it freezing?

By Chris Green (not verified) on 16 May 2008 #permalink

Actually, I found a description and video of (very informal) supercooling ( but, if it is so simple, I wonder why this doesn't happen regularly in the ice cubes trays in one's freezer. Any ideas?

By Chris Green (not verified) on 16 May 2008 #permalink

I thought the Vonnegut thing was "ice nine", not five...

Here's my guess: freezers aren't still. When you walk across your kitchen floor or when the compressor kicks in, it generates vibration.

I think I saw that in a porn movie once........

I'm sure a physicist will correct me, but I think normal water is too impure. Water needs some impurities to start freezing around, and there's enough in normal water (things like air) to start it.

The person doing the pouring isn't wearing any gloves. They're nuts!

Liquid water will supercool if [1] it's extremely pure, [2] there aren't any suspended sediments or rough or dirty spots on the inside of the container for crystals to form around, and [3] it isn't disturbed by vibration or sudden motion. The best-known case of this is the ice storm - supercooled raindrops freeze solid when they hit cold surfaces.

Water will also superheat under exactly the same conditions. That's why some people say not to boil water in a microwave oven. Superheating can occur in extremely rare cases, and when the superheated water is disturbed it will boil suddenly and violently. But because tap water is full of dissolved and suspended impurities and the containers are rarely if ever completely smooth and clean, you're highly unlikely ever to see it happen.

Superheating is a big concern in chemistry labs due to the use of de-ionized water and extremely clean glassware. That's the reason for "boiling chips" - putting a tiny sliver or two of something with rough surfaces in the flask is enough to promote the formation (nucleation) of bubbles and enable the water to boil normally.

I used to ROFL at some of my college labmates who were so scared of the possibility of "bumping" (as that sudden violent boiling is called) that they'd put tons of boiling chips in everything. One of my freshman lab classmates decided to have a bit of fun one day by replacing one of the scaredycats' supply of boiling chips with rock salt. The poor kid freaked when all his "boiling chips" kept disappearing and would put a few more in to replace them, and so on........

We were such a bunch of meanies. Sometimes I'm amazed that no one ever got hurt! I'm even more amazed that none of us got kicked out of there for stuff like that.

p.s. The experimenter in this video does get safety credit for using a plastic bottle. The sudden expansion of instantaneously freezing water would blow broken glass all over the place.

By themadlolscientist (not verified) on 16 May 2008 #permalink

Hmm, at -20C, I'd expect about a quarter of the water to freeze. (Heat of fusion is 80c/g.) Given that, the result is surprisingly slushy.

By David Harmon (not verified) on 16 May 2008 #permalink