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Acid-base chemistry is a foundational concept for organic chemistry, and the complexities in teaching and learning acid-base chemistry are well documented. This study aimed to investigate post-secondary instructors' pedagogical content knowledge (PCK) for teaching acid-base chemistry in an organic chemistry context. Two groups of three graduate teaching assistants and one group of three faculty instructors constructed content representations (CoRes). The three CoRes generated by these groups were qualitatively analyzed and organized into a summary compiled CoRe. Analysis of the compiled CoRe revealed eight major concepts of organic acid-base chemistry as defined by these instructors. Three major concepts were identified as foundational definitions, and five were identified as concepts that build upon these definitions. We arranged all eight concepts into a progression. Analysis of the compiled CoRe also revealed that instructors primarily leverage students' prior knowledge when teaching acid-base chemistry. Our results serve as a reference for organic chemistry instructors and may inform further research on the instruction of organic chemistry.

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 spontaneity 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.

Lewis structures are fundamental to learning chemistry, yet many students struggle to develop a complex understanding of its meaning and uses. Writing-to-Learn supports students in developing a deeper conceptual understanding of the topic, making it an ideal pedagogy to apply to student learning of Lewis structures. One difficulty often associated with classroom writing is the capacity of instructors to provide feedback to each student on their written work; however, this practical constraint can be mitigated through incorporating peer review. Peer review and revision are known to support conceptual learning and yet are underutilized in STEM (Science, Technology, Engineering, and Math) classrooms. Additionally, peer review is an authentic, common, and necessary practice in chemistry research, which warrants its incorporation early on in chemistry courses. A major concern regarding the use of peer review-based feedback is the ability of students to provide concept-based feedback that is both correct and detailed enough to enhance student understanding and support substantial revisions. In response, this work investigates the relationship between revision and the characteristics of students' peer review comments in the context of a Writing-to-Learn assignment focusing on student understanding of Lewis structures. Chemistry students wrote a summary of Lewis' 1916 paper introducing Lewis structures, participated in peer review, and revised their work in response to a structured prompt detailing specific chemistry concepts to be covered. The peer review comments and students' revisions were thematically analyzed. The peer review comments were deductively analyzed according to an analytical framework to characterize the usefulness of comments. The extent and type of student revisions were also analyzed and paired, if relevant, with the associated peer review comments. Results indicate that students provided both detailed and conceptually focused comments on their peers' work, irrespective of specific chemistry content being addressed. Although the assignment and peer review rubric were content focused, students made a mixture of editing and content revisions following peer review. These results suggest that further scaffolding of what constitutes good feedback and revision may further promote student learning.

Graduate students play a critical role in undergraduate education at doctorate granting institutions; but generally have minimal opportunity to develop teaching expertise. Furthermore, little is known about how graduate students develop teaching expertise in this context. We investigated the development of topic-specific pedagogical content knowledge among chemistry graduate student teaching assistants (GTAs). Thin layer chromatography was selected as the topic of investigation because undergraduate students encounter it throughout organic chemistry lab and it is connected to several foundational chemistry topics. An instrument was developed to measure both content knowledge (CK) and pedagogical content knowledge (PCK) of thin layer chromatography for GTAs with a range of teaching experience. Data from the test instrument were transformed using the Rasch model and statistically analysed. Our analysis showed that graduate students at all levels of experience performed well on content knowledge questions, but even experienced GTAs demonstrated low levels of pedagogical content knowledge. Importantly, experienced GTAs demonstrated a greater proficiency than novice GTAs, which suggests that pedagogical content knowledge is developed over time.