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Q:
Does tapping the top of an unopened soda container reduce the risk of "soda explosion?"
- Mike
Columbus, Ohio
A:
The best way to keep soda from exploding is to let it sit for a long
time at a low temperature before opening the can or bottle. The reason
for this is that the solubility of carbon dioxide in water is larger at
low temperatures than at higher temperatures. So the equilibrium
pressure of CO2 over the soda will be less when it is cold than when it
is warm, and less will bubble out at a high rate when the can or bottle
is opened.
This effect is an interesting case of positive feedback in the
greenhouse gas cycle. As the oceans warm, they give up carbon dioxide
because of the decreased solubility in warm water, amplifying the
greenhouse effect, causing the oceans to warm even more. Some
scientists refer to climatic "switches" where a small nudge in one
direction can cause a much amplified response.
Tom
p.s. As far as tapping goes, it should help. The reason is that
small bubbles can be stuck to the sides in the liquid. When the
pressure is released these bubbles grow rapidly, driving some liquid
out. If you tap on the can, you should knock the bubbles loose so they
rise into the gas above the liquid. That can escape without carrying
any liquid with it. There will still be new bubbles forming in the
liquid, but that will go much more slowly if there aren't large
starting bubbles stuck in there.
Mike W.
(published on 10/22/2007)
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