# Is a given volume of sparkling water lighter or heavier than the same volume of still water?

I can see it two ways - if all the $CO_2$ has turned into bubbles I would imagine it is lighter. However dissolved $CO_2$ atoms are probably heaver than the $H_2O$ atoms they replace, or fit in between.

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The density will be a little bit higher than 1 g/cm³, because the carbon dioxide will be partly disolved as hydrocarbonic acid anion and protons.This and solvation of the quadrupole dioxide make cause solvation water (in vicinnty to ions) which is denser than normal water. (Again that special low density water structure, which explains most of the irregularities of water!) – Georg Nov 4 '11 at 15:02
@Georg do you want to make that an answer. – paulmorriss Nov 7 '11 at 9:08

The solubility of $\text{CO}_2$ in water at 0C is about 3.5g/kg of water. If the volume of water does not change by more than 0.35%, which I would expect, then one liter of $\text{CO}_2$ saturated water will be heavier than one liter of pure water.