How better to learn about density then with candy bars? Kit-Kat bars are peanut-free, even though no one eats them in class. I purchase mini, regular and king-sized Kit Kat bars for the class.
This lab allows students to explore density. In groups of 4, they measure the candy bar's length, width and height with the ruler. They measure its mass with the triple beam balance. Using a calculator, they find the volume of each candy bar and then the density. What they find is that each candy bar has the same density, regardless of its size.
It takes one lab period to complete, and I use it after students have practiced with the volume and density equations.