Resumen de Mental Rolodexing: Senior Chemistry Majors’ Understanding of Chemical and Physical Properties
Ryan S. DeFever, Heather Bruce, Gautam Bhattacharyya
Using a constructivist framework, eight senior chemistry majors were interviewed twice to determine: (i) structural inferences they are able to make from chemical and physical properties; and (ii) their ability to apply their inferences and understandings of these chemical and physical properties to solve tasks on the reactivity of organic compounds. The latter included predicting the behaviors of natural products under acidic, basic, nucleophilic, and electrophilic reaction conditions and designing molecules based on a set of constraints. Content analysis of the data revealed that the students’ conceptualized a substance’s phase (of matter) at ambient temperature and pressure primarily on molecular size and intermolecular forces, but did not consider molecular shape or any thermodynamic factors. This oversight of molecular geometry also manifested itself in the students’ conceptions of molecular polarity and solubility in water, both of which were based solely on the presence of heteroatoms. Furthermore, the students were unable to articulate their conceptions of chemical characteristics such as acidity/basicity and nucleophilicity/electrophilicity. In the application tasks, the participants experienced considerable difficulty with components requiring them to integrate multiple concepts. These results are interpreted in the context of lingering concerns that current chemistry/science instructional practices lead to students developing knowledge bases consisting of numerous isolated facts with relatively few connections between them. We conclude with some suggestions for helping students in undergraduate organic chemistry courses to develop more robust and integrative conceptual frameworks.
