Does sparkling water weigh less than normal water, and if yes, by how much?

Is it im-perrier-tive that you know? It is fizzycally difficult to weigh water that isn't still.

Eau Eau Eau said Santa

Using identical glasses and filling each of them with equal volumes of still and sparkling water, Professor Shaker weighed two identical empty glasses separately. He then filled each glass with equal volumes of still and sparkling water.
He then weighed each separately. After deducting the weight of the empty glass, the Prof. came to the conclusion that still and sparkling water weigh exactly the same.

NB: This experiment was conducted under strict laboratory conditions, namely Shady's kitchen sink

By the heck SS, your kitchen must contain some high tech equipment. Scales that can weigh down to the nearest picogram (or better) and glasses that are so similar it is impossible to squeeze a single H2O molecule more in 1 glass than the other.
WOW !

Same weight of water.
If not it have more salt.

Sorry CQ but salt is irrelevant.

I have actually posted this question to a scientific source in order to get a correct response since I have been unable to find anything on the web to back up my conclusion.

I believe sparkling water is heavier than still water.

My reason for this is quite simple although there may be 2 manners in which it applies.
All chemists that know Avogadro's number and the MOLE (not the almost blind furry animal that lives in the ground) I am sure will agree.

A Gram Molecular Weight of any substance contains Avogadro's number of molecules

Avogadro's number is 602,213,670,000,000,000,000,000

The atomic weight of Hydrogen is 1.
A molecule of Hydrogen is H2.
If I have Avogadro's number of molecules of H2, they will weigh 2grams

Oxygen "O" has atomic weight 16.
So water (ie H20) has atomic weight of 18 (2 x H @1 each + O @ 16)
This means if I have Avogadro's number of water (H2O) molecules they will weigh 18 grams in total.

The fizz in sparkling water is Carbon Dioxide (CO2)
C has atomic weight 12 so a molecule of CO2 is 44 (12 + (2 x 16)) and an Avogadro's number of them will weigh 44 grams.

If I maintain the same number of molecules, so that if I add a CO2 I must remove a H2O, then that number of molecules slowly gets heavier since H2O is 18 and CO2 is 44.
Alternatively I could maintain the same weight by removing 44 molecules of H2O everytime I add 18 molecules of CO2.
Either way the "sparkling" mixture is denser and therefore heavier than the "still"

The reason I am not totally sure that this explanation is totally the case is that the CO2 is DISSOLVED in the H2O and a different set of dynamics that I am unaware of may apply.

However, given that STILL water contains dissolved AIR (basically 80% Nitrogen and 20% Oxygen)) if it ALSO contains large quantities of CO2 AS WELL, then it MUST be heavier.

One caveat:
IF the CO2 displaces some of the Nitrogen and Oxygen (on the basis that to dissolve CO2 in the water some N2 or O2 must leave it) then potentially it could be lighter since N has atomic weight 14 (N2 = 28)
So if a N is ejected to accomodate a C, then 14 -12 is a net reduction of 2.

Having said all that, that last case would be under very unusual circumstances, since the CO2 in fizzy water is contained by being under higher than atmospheric pressure. Hence when opening the bottle, all the bubbles turn into gas from the previously dissolved state.

As to the last part of the question "by how much" ?
Depends how "fizzy" or how "flat" your sparkling water is !