I got a beer out of the freezer last night and opened it, only to realize that it was almost frozen, so I left it to warm up. 10mins later I hear a dripping noise and realize that the beer had overflowed and was starting to spill off the table.

What causes this slow expansion of beer after it is warmed from a near 0°C temperature?

  • Melting takes time.

  • As your beer is thawing, temperature remains roughly constant. Then the beverage will slowly assume ambient temperature.

  • Solubility of gases (e.g., $\ce{CO2}$) in common solvents usually decreases with warming. This is because the breaking of solvent$-$solvent interactions are not compensated by new interactions between solute and solvent. In other words, solubility of gases is often exothermic.

The bottom of the beer might have warmed more quickly, causing a buildup of carbon dioxide under a layer of still-frozen beer. Reaching some critical value for pressure, the top popped. According to Henry's law, immediately after even more gas bubbles are formed.

Effects due to positive thermal expansion of beer are probably rather small but these would only aggravate any overflow.

For further reading on similar subjects, see

  • $\begingroup$ Are you using popped figuratively? Because he stated the beer container (can? bottle?) was opened before it was warned. $\endgroup$ Dec 16 '16 at 4:01
  • $\begingroup$ @electronpusher Pretty literally I think. In this case, it was the cylinder-shaped beer ice in the neck of the bottle that might've popped. I am actually quite surprised that the mess didn't occur in his freezer; in general, expanding ice will have done the opening for you ;) $\endgroup$ Dec 16 '16 at 8:37
  • $\begingroup$ I'm also surprised the expansion didn't break the container in the freezer. Is it possible that all of the pressure built up during the expansion of water to ice was somehow stored as a potential energy? Thus when he opened the container the pressure was not immediately dissipated, but as it thawed this potential energy was released or converted to drive the expansion...? $\endgroup$ Dec 16 '16 at 14:23

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