Imploding Soda Can

I have a can of RC Cola in my fridge that has imploded. I bough it about a year ago in a 12-pack. When I pulled it out of the case, the sides were all sucked in, as though somehow the air had been sucked out of the can. I thought that it was pretty darn wierd, so I set it on the counter. When I came back later, the can had returned to normal pressure. Thinking that this was even wierder, I put it back in the fridge, and after a few hours it had re-imploded. I just cleaned out my fridge, and found it in the back corner.

My question is, how the hell could this happen? It seems contrary to the laws of physics to me.

It has to be caused by a pressure differential between the inside and the outside of the can. I bet the soda is flat, and the air remaining inside lowers its pressure in the cold, allowing atmospheric pressure to squeeze the can. That’s my best guess.

Q.E.D. has it right, but the question is why is the soda flat? Why doesn’t this happen more often?

The fizz in a soda drink is because it is saturated with dissolved carbon dioxide at the packaging pressure. When you release that pressure, the gas is now supersaturated and so comes out as bubbles.

Lowering the temperature has two effects - it increases the solubility of the carbon dioxide in the liquid, and it reduces the pressure of the gas in the headspace. (Unlike solids dissolved in liquids, the solubility of gases in liquids goes up with reduced temperature.) Both of these act to reduce the can’s internal pressure. Whether it’s enough to lower the internal pressure below atmospheric under normal circumstances, I don’t know. Possibly you have an underfilled can, so the headspace is larger. It’s also possible that the cola simply contains less dissolved carbon dioxide than usual due to manufacturing/packaging variation.

Those two sound like the most likely. Weigh the can. Compare it to another similar can.

There’s no simple test for carbonation, so don’t open the can yet.

Someone else may think of another test that needs to be done first.