Chemical processes can be fully explained only by employing quantum mechanical models. These models are abstract and require navigation of a variety of cognitively taxing representations. Published research about how students use quantum mechanical models at the upper-division level is sparse. Our work aims to fill this gap in the literature and begin the process of characterizing learning of quantum chemistry in upper-division courses. We posed the following research questions: RQ1) How do undergraduate physical chemistry students develop quantum mechanical models? RQ2) How do undergraduate physical chemistry students select quantum mechanical models to explain various quantum chemical phenomena? To address the research questions, we developed a mixed-methods study centered on the use of two tools: Tool 1) Think-aloud interviews in which participants were asked to construct a model of the hydrogen atom. Tool 2) A quantum chemical model rating task that characterizes how students choose models to solve a variety of quantum chemical problems. The major findings are that upper-division students’ knowledge is significantly fragmented with a retention of determinism and reluctance to apply mathematical formulae. Students, unlike experts, focus on surface features. Our data indicates two specific surface features: lexical features and a “complex equals better” heuristic. We analyze the data through the lens of Chi’s framework which casts fragmentation as a problem of ontology.

Upper-division chemistry students' navigation and use of quantum chemical models: A fragmented conceptual landscape

255th National Meeting (2018)

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