Suppose I take a one-liter bottle of Coca Cola, measured to contain exactly 1000 cc of that drink. Then I let all the fizz escape in some magical manner that prevents any of the liquid from evaporating. What is the volume of the remaining liquid?
This question presumes that when we began, there was a certain amount of carbon dioxide present (dissolved?) in the liquid. When the CO2 escapes, it is a gas, and is of indeterminate volume, because it will fill whatever container it is in (as per the definition of “gas” as I remember it from high school). But while it is still in the Coke, it must be occupying some non-zero amount of space, right? I’m simply curious how much space that is.
And if the answer would be different for other drinks (beer, bubbly wine, selzer, etc) I’m curious about the differences too.
The gas fits in between the liquid molecules. Even dissolving a solid does not increase the volume of a liquid until the solution is saturated and some solid does not dissolve.
Now that the OP has been answered, (thank you, btw, I didn’t know that) let me ask a related question.
Plants like CO2 in the air. Some pot growers I knew even had CO2 generators in their grow houses. Why not water them with carbonated liquids? (it’s what they crave)
You may visualize that better, perhaps, with salt dissolved in water: it is denser than pure water. Why? Because the volume does not increase, but the mass does.
When I make simple syrup, I usually mix a cup of water and a cup of sugar. All the sugar dissolves. The resulting syrup is definitely more than a cup (though much less than 2.) I don’t think it’s true that dissolving a solid doesn’t increase the volume at all.
When you make syrup you go beyond saturation, thus it becomes thicker. You melt the sugar and mix it with the water: mixing two liquids is not dissolving a solid in a liquid, the volume increases. I suggest this experiment: take a bottle of water and fill it to the brim. Take a little water out and keep it aside, now there is some space in the bottle. Dissolve a table spoon of salt in the bottle. Wait for the water to cool again, as dissolving salt is slightly exothermic and the heat increases the volume a little. Then pour the water you set aside back. The bottle does not overflow.
I’ve actually been wondering about this, because I’ve been filling up my hummingbird feeder with 3 cups of water and 1 cup of sugar, but I knew it couldn’t fit 4 full cups of liquid; but I wasn’t sure whether if I carefully measured I’d find that the water level doesn’t increase at all once sugar is added, or somewhere in between “no increase” and “full cup increase”.
It depends on how much sugar you use - as noted, I fill my bird feeder with a mix that’s 1 part sugar to 3 parts water and if it increases in volume the change is negligible.
The point isn’t that the sugar is dissolved, the point is that if you add sugar to water you get sugar water, but if you keep adding sugar eventually more sugar simply will not dissolve in the water. If you keep adding enough sugar and prevent crystallization, you get syrup.
So syrup will have more volume than water because the sugar you added to the water filled it up, and then you kept adding more and more.
Somewhere between is the correct answer. If volume 1 is added to volume 2, the total volume Vt will be less than V1+V2, but greater than either V1 or V2.
In high school chemistry experiments, students are often told to assume the solution volume doesn’t change because it’s negligible for that experiment, but it certainly does change.
When you add table salt (sodium chloride, NaCl) to water, the salt dissolves into ions, Na+ and Cl-. The volume increases by a small factor, but the mass increases by a bigger factor.
As I noted this was something I did not know previously but had been wondering about recently. I found this PDF about the chemistry of syrup - relevant quote:
Yes but negligible really is the key here. For example, while researching this I learned that when you start adding salt to water, it actually DECREASES in volume at first, because the salt’s polarity allows the water molecules to pack closer together.
The answer isn’t V1 or V1+V2, but it is MUCH closer to V1 than V1+V2 until you supersaturate the liquid.
“Syrup” isn’t a phase of matter, it’s just a layman’s description of liquid with a certain density and viscosity. If you add enough sugar that the solution is saturated, the excess sugar remains a solid. In order to get liquid sugar, you have to get it above its melting point of 186C (367F).
The discussion of maple confection you linked deals with supersaturated solutions, which is not at equilibrium. Weird things can happen in such solutions, and you aren’t getting anywhere near those conditions with the humming bird syrup you’re mixing.
Negligible is not the key if you’re asking about a scientific answer to the question if the volume changes.
The issue of the sum of the volume of two different substances not being equal to the sum of the volume of the substances combined is the reason I absolutely detest that alcohol is generally quoted as “by volume”. In my mind, that’s a totally useless way to look at the alcohol-water mixture. It’s not clear at all from the name what the numerator or denominator are of the fraction used the calculate the ABV %, whereas doing it by mass it is extremely clear. Obviously brewers have decided on a standard way of calculating it, but I as a chemistry student after learning about what happens when you add alcohol to water found the idea of ABV way too nebulous.
To address the original question about volume changes due to dissolved CO2, I found an article on volume changes in seawater with added CO2. I have no idea how to apply that to CO2 under pressure in soda, but it’s data nonetheless.
Natural seawater, initial volume = 86.5 cm3
Added CO2 (millimoles)
Volume change (cm3)
0
0
0.0384
0.00112
0.0597
0.00179
0.0840
0.00260
0.1206
0.00378
0.2374
0.00774
0.3513
0.01152
In other words, for the largest addition of CO2 in the experiment, the volume increased by 0.013%.
A: You don’t want to over-water, and the amount of CO2 in an appropriate amount of water is insignificant compared to the volume plants breathe in and out.
B: Plants have a gas exchange system set up to absorb gasses from the air. Now those gases will then be transported through liquid, but that doesn’t mean there’s an efficient pathway from the roots for CO2 dissolved in absorbed water.
C: CO2 makes the water acidic. That might be bad for the plants.
D: CO2 stays in the water while it is under pressure. Once it is out of the can it starts coming out of solution. Adding nucleation sites speeds up that process. Using it to water a plant adds a lot of nucleation sites.
Typical simple syrup for mixed drinks comprises 1:1 or (2:1 for rich syrup) sucrose:water by weight or volume (people have strong opinions both ways – no need to get into that now.) Heat will make it dissolve faster but is unnecessary; this solution isn’t saturates. Some complain that heating will hydrolyze some of the sucrose but I don’t know how much of an issue that actually is.
A little more data: I found a study of bubbles in soda that showed a range of CO2 concentration of 74-156 millimoles/L, which is 20-30x times the amount of CO2 added at the highest concentration in the above experiment. If it continued the roughly linear increase shown above, you’d expect a volume increase in the soda of 0.25-0.4%, so your original 1000 ml of soda might drop to 996 -997 ml with the CO2 removed.
But assuming a linear increase is a very poor assumption with the increased pressure, so I expect that’s not exactly the right answer.