Learning to reason through organic reaction mechanisms is challenging for students because of the volume of reactions covered in introductory organic chemistry and the complexity of conceptual knowledge and reasoning skills required to develop meaningful understanding. However, understanding reaction mechanisms is valuable for students because they are useful for predicting and explaining reaction outcomes. To identify the features students find pertinent when explaining reaction mechanisms, we have collected students’ written descriptions of an acid-catalysed amide hydrolysis reaction. Students’ writing was produced during the implementation of Writing-to-Learn assignments in a second semester organic chemistry laboratory course. We analysed students’ written responses using an analytical framework for recognizing students’ mechanistic reasoning, originally developed with attention to the philosophy of science literature. The analysis sought to identify the presence of specific features necessary for mechanistic reasoning belonging to four broad categories: (1) describing an overview of the reaction, (2) detailing the setup conditions required for the mechanism to occur, (3) describing the changes that take place over the course of the mechanism, and (4) identifying the properties of reacting species. This work provides a qualitative description of the variety of ways in which students included these features necessary for mechanistic reasoning in their writing. We additionally analysed instances of co-occurrence for these features in students’ writing to make inferences about students’ mechanistic reasoning, defined here as the use of chemical properties to justify how electrons, atoms, and molecules are reorganized over the course of a reaction. Feature co-occurrences were quantified using the lift metric to measure the degree of their mutual dependence. The quantitative lift results provide empirical support for the hierarchical nature of students’ mechanistic descriptions and indicate the variation in students’ descriptions of mechanistic change in conjunction with appeals to chemistry concepts. This research applies a framework for identifying the features present in students’ written mechanistic descriptions, and illustrates the use of an association metric to make inferences about students’ mechanistic reasoning. The findings reveal the capacity of implementing and analysing writing to make inferences about students’ mechanistic reasoning.

Thermodynamics and kinetics are key topics in the chemistry curriculum that pose challenges to students across a range of educational levels. These struggles arise from the complexity and mixed representations inherent to the topics. Additionally, while thermodynamics and kinetics are related, students struggle to make conceptually correct connections, sometimes seeing them as two separate topics with no relation and other times conflating their meanings and explanatory powers. Herein we captured student conceptions about thermodynamics and kinetics through a Writing-to-Learn activity that utilized peer review and revision to engage students with the concepts by applying them to a real-world context. This study identified whether students focused on the concepts targeted by the assignment and characterized the chemistry content of the peer review feedback. Students’ descriptions of thermodynamics and kinetics content, as well as the relationship between the two and how they connect to the application given in the assignment, improved during the process and suggests that peer review and revision played an important role in supporting students to describe these concepts. When guided by a content-focused peer review rubric, students provided constructive chemistry content-directed feedback. Specifically, analysis of student writing and comments demonstrated the potential of the assignment to engage students in building connections between complexly related topics, including distinguishing between sponteneity and rate and appropriately relating activation energy and rate. Findings from this study suggest that writing can be used to elicit student-specific conceptions of physical chemistry topics and develop students’ explanatory skills of chemistry content even without direct instructor feedback.