Use Chemistry to Solve a Crime! This Chemistry Module can be used as a whole unit using the concepts of separating mixtures (chromatography), solutions (acids/bases), density, and chemical and physical properties (testing powders) to solve a crime. At the end of the unit, students use scientific evidence from each lab in addition to interviews from the suspects and additional evidence found by the North Pole Police Dept. to logically determine who is guilty of stealing cookies from Mrs. Claus.