Opening warm soda bottles v. cold ones

[Leo Bloom]

I'm sorry if this has already been asked and answered in GQ. But,

Opening a fresh bottle of warm, stored-upright soda creates a geyser, whereas opening one stored in the fridge is relatively risk free. Why is that?

Intuitively I would have thought the opposite, but there you are.

[Bill Door]

The solubility of gases in liquids decreases with increasing temperature. At 0 deg C water will hold around 3.4 g CO2 per kg, at 20 deg C it's around 1.6 g/kg, less than half as much.

[TBG]

Stick the pop bottle in the freezer for a few hours (plastic bottles only!) if you really want to see it shoot when you open it. Just make sure the cap isn't aimed at anyone. Now you know why I once had to clean pop off a 15' high ceiling.

[Harmonious Discord]

Bill Door gave you the correct answer.

Cooling soda to just before it solidifies is a completely different monster. The release of pressure allows the instant freezing of the liquid as the gases try to escape. Water expands on freezing.

Both cases result in explosive decompression by the gases coming out of solution for different reasons.

[Napier]

Originally Posted by Harmonious Discord

Cooling soda to just before it solidifies is a completely different monster. The release of pressure allows the instant freezing of the liquid as the gases try to escape. Water expands on freezing.

Are you saying the expansion of the water on freezing helps propel escaping gas? This volume change is pretty small. It must be smaller than the elasticity of the plastic bottle when cold, as the bottles usually don't split open if left in there to freeze solid. I think it's more important that freezing water tries to crowd out things in solution, including air. This is also the mechanism that crowds air into separate distinctively shaped bubbles inside of ice cubes, which freeze from the periphery in.

[Harmonious Discord]

Originally Posted by Napier

I think it's more important that freezing water tries to crowd out things in solution, including air. This is also the mechanism that crowds air into separate distinctively shaped bubbles inside of ice cubes, which freeze from the periphery in.

This is what I was getting at. The gas is being forced out of solution by the freezing water.

[Machine Elf]

Originally Posted by Napier

Are you saying the expansion of the water on freezing helps propel escaping gas?

No. The water is cold enough to freeze, but can't freeze because the pressure is forcing the gas to remain in solution. When you open the cap, the gas really, really wants to come out of solution, faster and to a greater degree than if the soda was simply chilled to, say, 40F.

So it's not the physical expansion of the freezing water that's pushing the gas out of the bottle, it's that the gas is coming out of solution faster and more completely than in non-freezing cases.