If I open and close a soda bottle of size every [y] minutes, without otherwise disturbing it, do the contents go flat at a faster, slower, or comparable rate to simply leaving the bottle sitting open? Do the values of x and y matter?
I’m not saying my marriage depends on the answer, but…
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Marginally slower. The pressure of the CO2 in the soda drives it into the headspace once you take the cap off. When you put the cap on, it pressurizes the headspace until it’s back at equilibrium and no more CO2 leaves the liquid until you take the cap off.
Shaking the bottle certainly makes the CO2 dissipate quickly. I’d suspect that moving the bottle as you remove & replace the cap will affect it more than anything else. I know you said “without otherwise disturbing it”, but is that really possible?
Assume [del]a spherical cow in vacuum[/del] it’s magically possible.
Ethilrist, it takes some time to build enough pressure to stop offgassing, though. I agree with “marginally,” I think, but there’s curves involved. I have a feeling if I keep thinking about this nonsense I will end up at calculus, dammit.
The dissolved CO2 is in equilibrium with aqueous bicarbonate and carbonate and with gaseous CO2 in the head space. The kinetics of dissolved carbon leaving solution is dependent on the partial pressure of CO2 in the headspace. Keep that low (bottle open) and the rate stays higher. I can’t give you numbers though.
This. I don’t drink soda anymore, but when I did, I treated that bottle as if it were filled with nitroglycerin.
I feel my method worked better than my wife’s method of squeezing the air out of the bottle.
At least, putting the cap on stops anything from flying in and drowning…
Surely squeezing the air out would reduce the pressure inside the bottle and draw more CO2 out of solution?
Less total pressure leads to less partial pressure of CO[sub]2[/sub], I’m assuming you mean from the bottle’s tendency to return to it’s original shape …
I think the wife is trivially correct at best … consider 0.1x volume of soda in an x volume container, we have 0.9x volume of air for the CO[sub]2/sub to occupy … whereas for 0.1x of soda in an 0.1x volume, we have 0 volume for the CO[sub]2/sub to occupy … thus more CO[sub]2/sub remains in solution …
However, the wife is stressing the solution and creating many more nucleation sites by squeezing the bottle … this doesn’t change the final equilibrium state but it will hasten the rate of dissolution … so if we’re unstoppering the container every hour or so, the husband may be better off; if we’re letting the bottle sit in the refer for a couple of weeks, then the wife is correct … and again trivially so …
I disagree. When you have a squeezed container, any outgassing does not considerably add to the internal pressure until the container regains its original shape. The liquid has to outgas a considerable amount just to achieve the same internal pressure the unsqueezed and capped container started with.
Tangentially related, did those 2 liter bottle soda pop pump thingies ever really work? My mom had one for awhile, but IMO once a 2 liter is opened then resealed, no matter how, the subsequent pours of soda go noticeably flat sooner within a day or so.
Can’t see how they would work. You pump the headspace full of pressurized atmospheric air, but the partial pressure of CO2 doesn’t change - and it’s that PP of CO2 that determines the rate at which CO2 comes out of solution; the presence of more O2 and N2 doesn’t matter.
I used one of those hand-pumps years ago and don’t think it made any difference.
I have used one of those table-top carbonation machines to re-carbonate flat Coca Cola and it worked great. Tasted good as new. Probably a wash cost wise in terms of supplying the carbonation machine vs going to the store to get another 2l bottle but the full bottle of flat cola was already cooled and the ones at the store tend to be room temp. It was an ecological net win since the 2l PET bottle wasn’t entirely wasted to transport cola that got poured down a drain undrunk.