Why Diet Coke floats on Water and regular Coca-Cola doesn’t?

If you put a can of Diet Coke in a swimming pool, it would not sink and still float. But, if you put a can of Coca-Cola into a pool of water, it would go down. One more fun fact is that the man who invented Coca-Cola was actually seeking a cure for the morphine addiction which he acquired during the Civil War, and he marketed Coca-Cola in that way.

In any case, primarily, this floating trick seems like it goes opposite physics because both cans are containing the same amount of liquid and of the same size. Obviously, a person who read physics or had taken a single class at some point, may know what makes a given object float in the first place, in the simplest possible sense, is that the only possible condition that an object could float, is that the object will displace excessive liquid (or sufficiently dense gas) which is more than its weight.[irp]

As looking back on to the famous scientific uses of the mass density, the earliest recorded usage was done by Archimedes of Syracuse, the ancient Greek mathematician. He used this phenomenon when the King probably asked him to resolve the issue that whether his crown was made from the same pure gold bar which he actually gave to his jeweler or not?

The King had a doubt that the jeweler stole some of the gold he had given to him. He thought that the jeweler has replaced the gold with silver. But the problem was that he couldn’t prove it unless the crown was melt and then compared with another gold bar of the same size and the King wasn’t willing to choose this option.

Finally, Archimedes marked a cunning plan to put the crown under water and measure the amount of water it moved out and this amount of water would be compared to the amount of water displaced if an equal mass of pure gold was submerged. If the crown would displace more water than the gold bar, then it meant that it had been made with less thick materials than pure gold and including silver in it.

Rumor has it that Archimedes just got this idea when he jumped into a bathtub full of water and water waves fell to the floor. He just came out running naked and loudly shouting on the streets Eureka! Which is a Greek word meaning “I found it”.

Sadly, but not perhaps surprising, both Archimedes’ eureka moment and the whole idea of him sinking the crown in water are believed to be the tale, credited to a well-known Roman scholar, Vitruvius, a full two centuries after Archimedes died.

Additionally, it is said that simply putting the crown in water wouldn’t have given clear-cut measurements for Archimedes to reach the conclusion whether the crown was containing a little silver or not?

Irrespective of the reliability of such tales, Archimedes’ name, in the long run, would always be linked with the idea of density and flexibility after he wrote about it in his milestone piece, On Floating Bodies: “If a solid lighter than a fluid is forcibly immersed in it, the solid will be driven upwards by a force equal to the difference between its weight and the weight of the fluid displaced.”

Today this idea is known as Archimedes’ Principle. So, getting back to the Fun experiment of floating cans of fizzy drinks. We know from all this that given a can of Diet Coke floats and a regular can of Coke sinks, in spite of both same models of cans containing the same amount of liquid, the ingredients combined in regular Coke must be thicker.

According to the statistics, a 12 ounce can of Coke has more density because it contains 39 grams of sugar, as compared to the sweetener in a can of Diet Coke which is 125 milligrams. This little difference in mass between both cans just so happens to outcome in the total mass of either can fall on any side of the normal density of water. The result of this is in floating of one can and sinking of the other.

Source: Business Insider