This series of lessons offered by the MIT Edgerton Center gives students several opportunities to work with physical and chemical changes and chemical reactions. The focus of this review is on the wet lab and Lego modeling of the chemical reactions. Students experiment with baking soda and calcium chloride in a bag. Then, students use Legos to build the reactants and rearrange them to form the products to prove not only the Law of Conservation of Mass but also that a chemical reaction did take place.