Reaction coordinate diagrams (RCDs) simultaneously depict both thermodynamic and kinetic information. Previous research in our group has documented the challenges that organic chemistry students face when interpreting the surface features of RCDs and when trying to connect these features to reaction mechanisms. In this research project, semi-structured interviews were conducted with second-semester general chemistry students. The interviews explored students’ understandings regarding the information encoded in RCDs and the use of RCDs to explain mechanisms typically taught in general chemistry. Findings from the analysis of these interviews were used to develop an assessment instrument grounded in students’ ideas and reasoning, the Reaction Coordinate Diagram Inventory (RCDI), to quantitatively measure students’ thinking and confidence when interpreting the kinetic and thermodynamic information encoded within RCDs. Data analysis from general chemistry and organic chemistry students at several institutions, including longitudinal data, is ongoing. A manuscript describing the development of the RCDI was published in the Journal of Chemical Education, and a manuscript describing the reasoning of students when choosing among particulate mechanisms that correspond to RCDs was published in Chemistry Education Research and Practice. A manuscript reporting the findings of a longitudinal study for students as they move from general chemistry to organic chemistry was published in the Journal of Chemical Education.