This laboratory experiment (Discovering and Comparing the Densities of Coke and Diet Coke) is written in the scientific format. Students make hypotheses regarding the densities of coke and diet coke, observe the physical properties, and use mathematical reasoning to discover the reason for the density differences between these two materials. Students are always shocked by the outcome of this experiment. This laboratory write-up can be used in isolation, or can be supplemented with comparison writing activities and further experiments. This experiment effortlessly combines both science and math; exploring the concept of density in an engaging and motivating way as well as allowing students to justify their scientific findings with mathematical proof.