Re: Why do some cans of Coca-Cola sink while other cans of Coca-Cola float?

Obviously, if some cans of sugared Coke sink, while others float, something 
is affecting the density of the "floaters". I can think of three 
possibilities, most of which seem unlikely given the rigorous quality 
control under which soft drink manufacturers operate.

(1) Different amounts of sugar in a given can. (More sugar is denser. 
Sugared soft drinks should sink! A substantial difference from can to can 
seems unlikely, as this would imply very poor quality control and an 
inconsistent flavor.)

(2) Different amounts of carbonation in a can. (Lack of carbonation would 
mean less mass in the can, thus lower density. Probably a very small 
difference.)

(3) Different amounts of liquid in a can. (Less liquid means less mass, and 
the can could float.)

Of these three factors, I would suspect the third. A small decrease in the 
volume of liquid in the can could cause a substantial change in total mass, 
and allow the can to float. You could check this by emptying a "sinker" and 
a "floater" into separate measuring cups (or graduated cylinders) and 
seeing if the volumes differ.

Susan Rollinson