Reaction Coordinate Diagrams (RCDs) play an important role in the chemistry classroom by allowing students to visually interpret thermodynamic and kinetic parameters that impact the energetics and rate associated with a chemical reaction. Previous research has highlighted students’ tendencies to readout surface features on a RCD and to associate the x-axis with “time” rather than a sub-microscopic molecular trajectory. However, little work has been done to explore why students associate the x-axis of a RCD with time in a kinetics context. To address this gap, a study was conducted to investigate how students interpret the graphical features of a RCD and how these interpretations impact their perception of the rate of reaction. The guiding research question: “How do general chemistry students conceptualize the points and trends on a reaction coordinate diagram to draw inferences?” structured the nature of the applied methods and analysis. Undergraduate general chemistry students were recruited (n = 16) and asked to interpret a series of RCD prompts in a semi-structured interview. The first two interview prompts tasked students with interpreting the points and trends along a RCD, while the final two prompts asked students to make a comparison between two RCDs. The Actor-Oriented Model of Transfer served as the primary theoretical lens and clarified how students drew upon relations of similarity between RCDs and past experiences to reason about the rate of reaction. Interview tasks and analysis were informed by the Graphical Forms and Value-Thinking and Location-Thinking frameworks developed within the chemistry and mathematics education research communities respectively. Results derived from this study revealed that the unproductive adoption of graphical forms and value-thinking reasoning by chemistry students was enabled by the association of the x-axis with time, while location-thinking was a productive route for interpreting the rate of reaction. These findings challenge the use of an x-axis during the preliminary instruction of RCDs in the general chemistry classroom and suggest that practitioners should consider a more accessible qualitative framing of the reaction coordinate.

General chemistry students’ interpretations of points and trends along a reaction coordinate diagram

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.