Why does beer freeze when opened in hot temperatures?

[reinaldo]

freezing Beer in the Heat!

Hey everybody!...

the other day i had a few Beers in the refrigirator...i went to get one and i grab one...it was liquid...it wasnt frozen as the others...then when i open it up...it started to frozen from top to botton continuosly!...it took like 15 seconds to do that!...then it was frozen completely!...the temperature outside was about 26º C...how the F... is that posible?...you have beer in the fridge all liquid...then you open it outside and it freezes completely in 15 secs...?...please someone explain that to me!...i was Amaze! Thanks!

 

[Danger]

I would suspect that it's because of the drop in pressure when the cap was removed.

 

[nasu]

You say:"it wasnt frozen as the others". Does this mean that the others were frozen? You had them in the freezer or refrigerator?
If the others were frozen it means that the beer was supercooled (at a temperature below freezing point but still liquid). Then the question is not why did it freeze when you opened it but why it didn't freeze before. Usually you can super-cool a fluid if it has no crystallization centers.

 

[Danger]

You say:"it wasnt frozen as the others". Does this mean that the others were frozen?

I missed that; good catch.

 

[reinaldo]

let me explain better...i put 3 beers in the freezer (the upper part of the refrigirator, where your put the meat and the ice)...the 3 beers started to get cold...then my girlfriend when and put 4 more beers in the freezer like 15 min later...

later on...i went and grab a beer for myself...the first ones where already Frozen inside the bottle!...but the last ones where still Liquid!...i grab one of those...and when i open it...it started to freeze gradually, continuosly from top to bottom and it freezed in 15-20 Seconds...i was shock!...how the hell that was frozen outside in such a weird and fast way!...i hope i made it more clear...

sorry for my english!...im from venezuela!...

 

[glueball8]

It was probability supercooled but needed a bit of movement for it to turn into ice.

 

[nasu]

In this case I think that the pressure is the key (as Danger mentioned above). At high pressure the freezing point goes down.
Let's say it goes to -2 C due to the pressure inside the can. If teh beer it's at -1 C when you take it out of the freezer, it's still above freezing at high pressure. When you remove the cap the pressure goes down and now the freezing point is 0C and you have beer at -1C. So it freezes.
I just made up the numbers, for example's sake. The effect of the pressure on the freezing point is is not very strong. But it also can make ice melt when you put pressure on it.
I'd like to try it, it looks a pretty cool experiment to see.

 

[reinaldo]

http://www.youtube.com/watch?v=n_H5ZIoZSBo&feature=related

Thanks bright wang!...thanks to you i found one with the beer!...But i didnt hit the bottle...i just grab it and open it...when i open it it freezed just like in the video!...by the way...i didnt use Corona beer as in the video...i Use Regional Light...Venezuelan beer!...

 

[reinaldo]

well Nasu!...a friend told me exactly the same as you did! he said its all about the pressure exactly as you explained it!...my friend said that it was by the Boyle Law of fluids...

 

[uart]

well Nasu!...a friend told me exactly the same as you did! he said its all about the pressure exactly as you explained it!...my friend said that it was by the Boyle Law of fluids...

Well it just goes to show that no matter how many people tell you the same story it can still be wrong. There are in fact three separate mechanisms at play here and the suppression of freezing point due to pressure is by far the smallest (almost insignificant) of them.

While the boiling point of water is strongly influenced by pressure this is not the case for the freezing point. For example a 1 degree C depression of freezing temperature requires over 12 MPa of pressure. This pressure is approximately 120 atmospheres, almost a thousand times more than the pressure in your unopened beer!

So if it's not the direct influence of pressure then what is the cause? Well it's two other indirect influences of the pressure drop that do the trick. The first one has already been mentioned by Bright Wang above. If kept still the beer can be supercooled to below it's normal freezing point without ice immediately forming. Once opened the bubbles provide nice sites for crystal formation and initiate the freezing.

The other mechanism that no one has mentioned is that the escaping gas is an endothermic reaction. When gas is dissolved into liquid it is exothermic (produces heat) and when this process goes in the opposite direction and the gas comes out of solution it is endothermic and absorbs heat. This is the same principle to how most refrigerants work, in other words the beer actually self-refrigerates to some extent when you open it! This is the predominant mechanism.