Hazel Class investigated growth by experimenting with chemical reactions using Mentos and Coke. They investigated both normal Coke and Diet Coke. They discovered that Diet Coke has a greater reaction because it contained artificial sugars whereas normal Coke contained corn syrup, resulting in a smaller reaction.
They also found that the reaction started after adding 4Mentos. This meant, when they tried to add 7 or more Mentos, they could not complete the experiment as the chemical reaction had already started. You may (or may not) want to try this experiment at home!