Two colorless solutions are mixed and after a brief induction period, the resultant colorless clear solution suddenly turns to a blue-black color.  Changing the concentration of reactants in this clock reaction changes the induction period.  The analysis of the data collected from a series of experiments of the iodine clock reaction is used to determine the order of a reaction with respect to the reactants and to determine the rate law for the reaction.  This demonstration can be performed to help students visualize how the Method of Initial Rates works.