To float or not to float

To begin the new chapter on Density and Buoyancy, we completed the Coke vs. Diet Coke density demo.  We decided to include Coke Zero in our demo to extend our line of questioning.

Before we started the demo, I asked students to make observations about each can. Students made sure to look carefully at the volume (355mL), as well as the ingredients in the soda.  We were quick to notice that Coke had 42g of sugar while Diet Coke and Coke Zero had none.

The demo is simple: place each 355mL can of Coke, Diet Coke, and Coke Zero into a large basin of water, and observe.  We each made a hypothesis about which cans would float and/or sink.  

Each class had varying hypotheses; some where closer than others. So, what were the results?

Coke sunk to the bottom, while Diet Coke and Coke Zero stayed afloat.  Why was that?

Simply put...density!  We learned that the density of water is 1g/cm3.  Therefore, the can of Coke had a greater density than water, while the cans of Diet Coke and Coke Zero had smaller densities.  We found out that the amount of sugar (high fructose corn syrup) in the regular can of Coke increased the mass of the can, while the tiny amount of artificial sweetener (aspartame) in Diet Coke and Coke Zero did not change its mass too much.

We used the following formula (Density = Mass/Volume) to calculate each can's density.  We learned that if the mass is greater than the volume, it will have a greater density; whereas if the mass is smaller than the volume, it will have a smaller density.