Resumen de Rolling the Dice: Modeling First- and Second-Order Reactions via Collision Theory Simulations in an Undergraduate Laboratory
Jessica Iribe, Terianne Y. Hamada, Hyesoo Kim, Matt Voegtle, Christina A. Bauer
The principles of chemical kinetics comprise one of the core topics that appear throughout chemistry. Standard kinetics lessons typically cover reaction rates and relative rates, rate laws, integrated rate laws, half-lives, collision theory, and the Arrhenius equation. They can also introduce a discussion of mechanisms as well, which may be the first time students become aware of the importance of actual reaction path in general chemistry. Such concepts are grounded in mathematical descriptions of molecular movement and probability factors, and the convergence of various new topics with mathematics can be challenging. In an attempt to make these concepts less abstract, we developed analogies utilizing dice in a can that provide a tangible way to experience the realistic meaning behind kinetics, and briefly introduce students to statistical thermodynamics. One version is designed as a general science workshop, whereas the other is aimed at physical chemistry courses. Kinetic energy is put into the system via shaking the can of dice, which is used to represent temperature in our model. The dice are tossed, and “products” are removed before the procedure is repeated. In a first-order kinetic simulation, a reaction is symbolized by dice facing “6” up after tossing. To simulate second-order kinetics, a hook and loop fastener is attached to the dice and a successful reaction is represented by the formation of a pair having two “6”s facing up. Students are able to experience the difference between first- and second-order mechanisms and to reason through the parameters that affect reaction rates and rate constants. The overall goal is to allow for self-discovery of the purpose behind the intersecting topics in kinetic theory by incorporating data collection, dimensional analysis, plotting, and derivation of equations.
