Untangling chemical kinetics through tangible and visual representation of matter

Abstract

Second semester General Chemistry students are introduced to Chemical Kinetics as part of their curriculum. Often, instructors require that students plot  Concentration vs. Time graphs for elementary chemical reactions as part of the learning process. Despite employing graphical tools, students often find it difficult to conceptualize conservation of mass (matter) under constant volume conditions and thus, are unable to accurately depict concentration changes that occur during chemical reactions. We propose that the use of elementary shapes (e.g. triangles, circles, squares) to represent different atoms in molecules facilitates the comprehension of chemical kinetics. Specifically, generation of “Concentration vs. Time” graphs rendered with the aid of tangible and/or pictorial representations of atoms using fixed numbers of distinct and representative shapes helps students visualize and track the conversion of reactant “R” into product “P” as a function of time. Importantly, it also helps understand that reaction processes “start” and “end” with the same number of atoms as the reaction progresses from reactants to products. Through such a proposed visual and/or tangible tool, students can visualize which compound is the limiting reagent; how much of the other reactant is “left over”; and how much product can be made.