Does a bottle of soda go flat faster if refrigerated

[TriPolar]

Continuing the discussion from Which of these items are in your refrigerator(s) (not freezer) right now?:

@TriPolar

Soda goes flat if you keep it in the fridge.

@We_re_wolves_not_werewolves

What?!! No! This is exactly opposite of the truth. The solubility of CO2 in water is inversely related to temperature; i.e. the lower the temperature of soda, the higher solubility of the CO2 and the more “fizz” it is able to retain.

@TriPolar

It goes flat because the lower temperature means more CO2 must be released to equalize pressure in the increased space inside the bottle after you drink some of it.

@We_re_wolves_not_werewolves

There is no “equalization” of pressure going on in the bottle. A cold 2 liter bottle of soda will have lower vapor pressure in the headspace above the soda in the bottle than a room temperature bottle, due to the reduced amount of CO2 in that space. More of the CO2 will be dissolved in the liquid.

@TriPolar

I’ll have to find the details, or maybe ask about this on FQ. The pressure in the open space will increase in an opened and resealed bottle. That pressure comes from the release of more CO2. More than required to pressurize a warm air space. The cold soda can hold more CO2, but has to release it to the air space until the pressure equalizes. Each time you open the bottle you lose CO2, but more if it’s kept cold and resealed. I imagine an open bottle in the fridge loses less CO2 than an open bottle out of the fridge, but both go flat faster than is practical. If you don’t believe me get two bottles of soda try it out. Surprised me when I first heard this and had no explanation but testing proved it out.

@We_re_wolves_not_werewolves

This is where you are getting tripped up. You are correct that more CO2 would need to be released to pressurize a cold vessel than a warm vessel TO THE SAME PRESSURE. But that is not what is happening here. The cold soda bottle has a LOWER vapor pressure of CO2 than the warm one. There is no “equalization” of pressure here. As for your observed results, I don’t know what to say, perhaps some minor differences in the amount of liquid in the bottle, or one was older than the other and had therefore already lost some CO2 through diffusion through the PET plastic of the bottle can account for the discrepancy, but in any case it does not correlate with what should happen scientifically.

[TriPolar]

Rats. Wanted this in FQ.

[What_Exit]

Done.

[TriPolar]

Thanks.

[commasense]

I’m interested in hearing more about the science behind this, but practically speaking are you suggesting not refrigerating soda after opening the bottle?

I like my soda cold, and pour my refrigerated soda over ice. With warm soda I’d have to use more ice and the soda would become more diluted. Not sure that’s a tradeoff I’d be happy with.

I find that soda in a 2-liter bottle only goes flat if I leave the last 8-12 ounces or so in there for more than a couple of days. Usually I consume it faster than that.

[Sylvanz]

I’d say no. We drink a lot of Coca-Cola. We use 2 liters. We don’t like warm pop, so in the fridge it goes. It will go flat if left in there more than a day or two. That never happens here. However, it would be flat if left warm after opening.

I was wondering about laying an unsealed bottle flat. We’ve found it goes flat very quickly that way. We haven’t done that for decades now.

[We_re_wolves_not_werewolves]

laying it flat would expose more surface area of the soda to the atmosphere inside the bottle. It seems intuitive that this would speed up the CO2 escape at the soda-atmosphere interface, but I’m not prepared to show that mathematically.

[TriPolar]

Maybe you know enough to resolve this. CO2 will move from soda into the air gap, right? The surface area may affect the rate, but the total amount that ends up in the air gap will be based on pressure and/or temperature, right? What determines the amount of CO2 that ends up in the air gap?

[We_re_wolves_not_werewolves]

@TriPolar

the total amount that ends up in the air gap will be based on pressure and/or temperature, right?

yes, but we need to take a step back. Soda is packaged under high pressure CO2, so the pressure in an unopened bottle is something like 2 or 3 atmospheres, and that is substantially all CO2 (no air). That’s why you hear a large hiss when you initially open it, there is a lot of gas pressure escaping! The soda itself is essentially super saturated with CO2, that is why you will see fizz and bubbles popping from the soda as soon as you open it. Once that pressure is relieved by opening the bottle, the soda is free to get rid of that excess CO2.

Now, once you open it and then reclose it, the space above the soda is initially all air at 1 atmosphere. CO2 will continue to slowly diffuse out of the soda into that airspace, creating a mixture of air/CO2 with a total pressure that will increase slightly above 1 atmosphere. The amount of CO2 that will diffuse from the soda is determined by Henry’s Law, which is dependent on the Henry Solubility of the gas. For CO2 in soda, the solubility of CO2 will decrease as the temperature increases, meaning the CO2 is less soluble as temperature of the soda increases, meaning more CO2 will diffuse into the airspace than it would if the soda is cold.

I need to make a BIG disclaimer here. I am not exactly talking out of my ass on this and I believe the above explanation is generally correct, but it’s been a LONG time since I’ve done physical chemistry. I would take any correction of the above with grace and would appreciate if someone can confirm, expand, or correct any of this.

[Machine_Elf]

@We_re_wolves_not_werewolves

yes, but we need to take a step back. Soda is packaged under high pressure CO2, so the pressure in an unopened bottle is something like 2 or 3 atmospheres, and that is substantially all CO2 (no air). That’s why you hear a large hiss when you initially open it, there is a lot of gas pressure escaping! The soda itself is essentially super saturated with CO2, that is why you will see fizz and bubbles popping from the soda as soon as you open it. Once that pressure is relieved by opening the bottle, the soda is free to get rid of that excess CO2.

Now, once you open it and then reclose it, the space above the soda is initially all air at 1 atmosphere. CO2 will continue to slowly diffuse out of the soda into that airspace, creating a mixture of air/CO2 with a total pressure that will increase slightly above 1 atmosphere. The amount of CO2 that will diffuse from the soda is determined by Henry’s Law, which is dependent on the Henry Solubility of the gas. For CO2 in soda, the solubility of CO2 will decrease as the temperature increases, meaning the CO2 is less soluble as temperature of the soda increases, meaning more CO2 will diffuse into the airspace than it would if the soda is cold.

I need to make a BIG disclaimer here. I am not exactly talking out of my ass on this and I believe the above explanation is generally correct, but it’s been a LONG time since I’ve done physical chemistry. I would take any correction of the above with grace and would appreciate if someone can confirm, expand, or correct any of this.

I came in here to say pretty much exactly this. Nicely done.

[Measure_for_Measure]

Semi-relevant thread debunking the fizz keeper:

Pressing Scientific Issue: Do Pump-Caps Preserve Soda Fizz?, Part II

There is a device called Fizz-Keeper, which allows the user to pump compressed air into soda bottles, thereby allegedly “preserving the fizz”. I am curious about this item’s effectiveness. A recent thread discussed this issue; I would like further details. (1) There are anecdotal accounts (including my own) that the fizz-keeper does indeed work. It is not necessary to add further casual observations. (I will not object if someone wants to bump this thread from page 3 though. ) (1a)…

More relevant internet link:

http://scienceline.ucsb.edu/getkey.php?key=2346

Like most gasses, carbon dioxide is more soluble in cold water than warm water. That means it is easier to carbonate cold beverages than hot beverages. If you heat up a soft drink, it will start to lose carbonation faster than if you kept it cold.

So I say reseal the bottle as fast as possible and keep it cold.

[TriPolar]

@We_re_wolves_not_werewolves

Now, once you open it and then reclose it, the space above the soda is initially all air at 1 atmosphere. CO2 will continue to slowly diffuse out of the soda into that airspace, creating a mixture of air/CO2 with a total pressure that will increase slightly above 1 atmosphere. The amount of CO2 that will diffuse from the soda is determined by Henry’s Law, which is dependent on the Henry Solubility of the gas. For CO2 in soda, the solubility of CO2 will decrease as the temperature increases, meaning the CO2 is less soluble as temperature of the soda increases, meaning more CO2 will diffuse into the airspace than it would if the soda is cold.

Does the amount of CO2 that dissolves in air increase as the temperature decreases?

[Sylvanz]

I could have told you that. I had one once, and they obvs don’t work.

[wolfpup]

@Measure_for_Measure

Like most gasses, carbon dioxide is more soluble in cold water than warm water. That means it is easier to carbonate cold beverages than hot beverages. If you heat up a soft drink, it will start to lose carbonation faster than if you kept it cold.

So I say reseal the bottle as fast as possible and keep it cold.

This. As also stated by @We_re_wolves_not_werewolves.

Colder water can hold more CO2 in solution than warmer water, so keeping soda cold and tightly sealed is the best way to preserve carbonation.

This physical fact is also relevant to the big issue of climate change. As the oceans warm, their ability to absorb CO2 from the atmosphere is reduced. It’s one of the feedbacks that can accelerate temperature rise.

[We_re_wolves_not_werewolves]

It’s not really “dissolving” in the air, it’s just mixing with it. And the answer is no as far as I know.

BUT, I just had an insight into why you might feel the room temperature soda holds onto its carbonation better than cold soda! Basically, since the CO2 is less soluble in the soda when it is warm, there is MORE CO2 in the airspace in the bottle in warm soda than the cold. Thus, the pressure in the sealed airspace is higher (making the bottle feel firmer), and you hear a bigger “hiss” when you open the warm bottle. But the actual warm soda itself will have less CO2 than the cold soda. The amount of the hiss and the firm feel of the bottle tricks you into believing there is more CO2 in the soda in the warm bottle!

[Measure_for_Measure]

@Sylvanz

I could have told you that. I had one once, and they obvs don’t work.

But could you have told me this over 20 years ago, the date of the thread?

[ASL_v2.0]

@tripolar, I think a lot of your confusion is premised on the same imperfect understanding of gas laws as when (some) people claim you should take care to slowly let the air out of your tires if driving south on a road trip. Their logic being that, if the temperature doubles, then the air pressure will surely double as well. The ideal gas law and all that.

But what they miss is that the temperature units in the ideal gas law equation are not Celsius or Fahrenheit, but Kelvin. While 5 degrees Celsius to 20 degrees Celsius (or even 40 degrees Fahrenheit to 70 degrees Fahrenheit) might seem like a huge increase in pressure should result, other things being equal, the proper comparison is ~278 Kelvin to ~293 Kelvin. Not quadruple the pressure, but perhaps a 5% increase, other things being equal.

Which is to say, that the increased temperature isn’t going to do a whole lot to raise pressure on its own. So if there is a significant increase in pressure, it’s more likely to be from more gas coming out of solution. That is, the “n” in PV=nRT is increasing much more dramatically than the T. And where is that extra n coming from? As others have said, out of solution, (all that Henry’s Law stuff) meaning your carbonated beverage is becoming less carbonated. Flatter.

[Sylvanz]

Why yes, I could have as that’s when I had it.

[md-2000]

@wolfpup

Colder water can hold more CO2 in solution than warmer water, so keeping soda cold and tightly sealed is the best way to preserve carbonation.

This physical fact is also relevant to the big issue of climate change. As the oceans warm, their ability to absorb CO2 from the atmosphere is reduced. It’s one of the feedbacks that can accelerate temperature rise.

There was a bit of trivia i read, that the reason the south polar waters was such a good place for 19th century whalers (besides “because they killed all the whales elsewhere”) was that the much colder water around Antarctica allowed a greater concentration of CO2 meaning more plankton could grow there.

[OldGuy]

I don’t use a fizz keeper, but I do squeeze the partially emptied 2 liter bottles to drive out as much air as possible before screwing the cap back on. It does seem to preserve the carbonation better.