The physics of freezing soda pop

I have the habit of keeping 12-packs of cans of soda in my trunk to take advatage in cooler weather of the natural refrigeration. Of course as it’s now colder than Satan’s taint the cans are freezing. But they don’t freeze uniformly. One can will freeze to the point of bursting, another will freeze solid but not distort the can, another will appear liquid but upon opening will turn to slush and some will remain liquid. This occurs regardless of brand, and within the same 12 all of these variations will be present. I would assume that cans from the same cases are filled under similar if not identical circumstances and will be prepared from similar if not identical ingredients, if not directly from the same batch. They are subjected to identical treatment in my possession. I can’t come up with any variation that would account for the differences.

This happens across brands, but the current brands in my trunk are Vault Zero, Diet Coke with Lime, Fresca Peach Citrus, Diet Squirt and a stray can or two of Dite Rite raspberry. I can post ingredients (but not proprotions) if that would be helpful.

I think supercooled and not frozen liquids represent a pretty unstable state, and the differences between the cans can be vanishingly small and still cause supercooled liquids to exhibit can-to-can differences.

I heard of a rare case of someone walking down to a lake one morning that was well below freezing but still liquid. He tossed in a pebble and the whole thing rapidly turned solid before his eyes. Now, this does sound far-fetched, but I do see surprisingly sudden changes when I pull a plastic bottle of seltzer out of the freezer. It usually has visible crystals forming on its inner surface, and doesn’t change much when I pull it out or open it. But sometimes it will appear uniformly liquid and will cloud over with slushy crystals within several seconds of being pulled out, or within several seconds of being opened.

There could be some nucleation issue here. Note that when a bottle of something fizzy is opened, often, the sites on the sides that produce streams of bubbles don’t look special in any way (though sometimes they have some visible roughening such as a chip or particle on the surface).

If you’re unfamiliar with the concept of supercooling…

http://en.wikipedia.org/wiki/Supercooling (Wikipedia article)
http://www.youtube.com/watch?v=fSPzMva9_CE (one of many amazing videos you can find)