Buoyancy - Pepsi And Diet Pepsi



To show the difference in density between soft drinks with and without sugar.


Cans of Pepsi and Diet Pepsi, tank with salted water.


Ask your students the question: When you dissolve a cup of sugar in a cup of water, do you get two cups◙of solution?

Setup Time

5 min.




    Unopened cans of Pepsi and Diet Pepsi are floated in a bath of slightly salted water. The Pepsi sinks, while the Diet Pepsi floats. The density of the Pepsi is increased by the dissolved sugar, which occupies space between the water molecules. Diet Pepsi has no additional sugar, and is therefore less dense.


    Joel Achenbach, Why Things Are, Coke? How Sweet It Is!, Washington Post, Wash., DC. ◙Walter Roy Mellen, Oscillations of Eggs and Things: Behavior of objects in fluids having densities that increase with depth, TPT 32, 474-475 (1994).