When I buy warm beer, and want to cool it off quickly, it normally gets put in the freezer for half an hour or so.
The other day it got left in a bit longer than normal. When opened it immediately froze - well, went from liquid to quite slushy/icy.
Anyone have a clue as to why this happens?
Does this happen for just beer, or do other carbonated beverages do this as well?
Quite odd, but quite cool.
Cheers! 
Super-cooled, perhaps?
I think it’s a function of the properties of liquids under pressure. When you open the beer they then have the same pressure as the outside area, eg, less pressure, so the liquid can change to ice slush. One of those Boyle’s Laws things (or it could be Henry, Charles, Dalton… the whole gang).
I would suggest that the transition was caused by decompression. The beer was probably below the freezing point of water–supercooled, like Crafter said–and the sudden expansion disrupted the solution. There would also have been a temperature drop upon decompression, but I suspect that it would be too small to matter.
I always thought that this effect occured because the freezing point of water decreases with increasing pressure (here’s a rough picture of the phase diagram for water, showing the decrease in freezing point with increased pressure. Interestingly, in most other liquids, the freezing point increases with increasing pressure). So your bottle of beer cools down to some temperature below 32 degrees F, but still above its freezing point at that pressure. Then, when you pop the top, the freezing point changes.
However, I always just assumed that; I don’t know. SO I’m willing to be wrong here.
This has happened with a large bottle of water at a restaurant once. The waiter opened it up and it proceeded to freeze right before everyone’s eyes. Pretty cool.
There are a number of things that change when you open the bottle; the pressure changes, gases come out of solution (and the bubbles themselves can act as nucleation points).
Heh. What’s cool is when it makes a popsicle ~ with the beer-ice creeping outta the longneck ~ hard to drink that way, tho; and it’s kinda weird to “eat” beer.
Usually when I leave a beer in the freezer, it explodes and becomes modern art.
Diet Coke does the same.
I routinely carry a case or two in the back of my truck. Only when it’s below 20 degrees F or so, do they freeze and explode. Usually I’ll bring a few inside and let them warm up a few minutes beofre popping one open, otherwise it turns to slush.
The interesting thing is, it takes a moment for the slush to form. If I’m quick, I can open it and get nearly a full drink in my mouth before the freeze happens and it quits pouring.
You mean a temperature rise, don’t you?
I’m pretty sure he didn’t, as that would be incorrect.
If it was supercooled, the temperature would rise to the freezing/slush point, right?
Close, but it’s known as the Joule-Thompson effect, IIRC. The mouth of the can is an orifice, and the piece you push in to physically open the can acted as a throttling valve as the CO2 escaped across the orifice. A throttling process is isenthalpic…meaning the enthalpy stays the same, but the pressure drops. On a thermodynamic table, one would look for the same enthaly value at the new pressure…yielding a new (lower) temperature. Therefore, the liquid may very well exhibit some freezing in the process.
This is why valves often ice up as condensate quickly freezes on the outside of a valve while gas is throttled across the interior of the valve body…across an orifice. - Jinx
Say I put a plastic bottle, a glass bottle and a can in the freezer. Does the container influence the time needed, or ability, to reach this state?
I’ll have to put a pop and bottle of water in the freezer and watch it happen. There must be a very fine line between frozen/explosion mess such as World Eater mentioned and the super-cooled liquid/rapid slushy formation state as experienced.
Brilliant description Jinx. Thanks.
Amazing the responses one gets when you talk about beer.
Have a great weekend everyone 
Yes. The material, size, and shape of the container will all have effects on the amount of time needed. Glass and plastics will conduct the heat more slowly than the aluminum can. A larger amount of liquid will take longer to reach the desired temperature. Similarly, if the container is rather squat but wide it will take longer than if it is a long narrow vessel. Of course, the volume of the liquid will also effect this process.
But, given that the expulsion of CO[sub]2[/sub] occurs for only a short period of time, and that the portion of the gas most affected winds up outside the can, I have a hard time believing that enough heat energy can be transferred to the remaining CO[sub]2[/sub] (or the metal of the can) to eventually freeze a substantial portion of the beer.
It doesn’t freeze solid though, just turns to slush, zut. This is a lot more plausible. However, I didn’t think alcohol froze at a temperature that can be reached by a cooler of ice. Don’t think even water can do that, it usually takes a lot longer. Not going to worry about specifics, just pointing that out.
The same slushy thing happens with mountain dew
This happens every single time with Smirnoff Ice, and yields a great alchoholic slushy. Just open it over the sink, because about an inch will squirt out as it’s freezing.