Bulk water is an essential component for dissolution-the process in which ionic compounds are broken down into constituent charged species. Water solvates ions, engages in hydrogen bonding, exerts electrostatic forces, and contributes to the effects of entropy and enthalpy. Despite bulk water’s importance, its submicroscopic presence is often omitted from high school instructors’ pedagogical practices. While the presence of bulk water may seem obvious to experts, such simplification may problematize novice learners’ sensemaking of aqueous reactions. This study thus investigates how the depiction of bulk water may affect a high school chemistry teacher’s ability to create comprehensive external representations of dissolution. Using phenomenography as our theoretical framework, we analyzed and compared dissolution representations produced by 19 teachers who were attending a four-day professional development program (PD). The results indicate that none of the representations had depicted the submicroscopic presence of bulk water while only two had indicated hydrogen bonding. As a result, these representations convey dissolution processes that are incomplete and/or scientifically inaccurate. Our findings suggest that the interactions of bulk water at the particulate level must be foregrounded in teacher learning. In this instance, less is not necessarily more. Simplification through omission, while appropriate in some contexts, carries the risk of fostering misconceptions of chemical phenomena. To ensure rigorous conceptual understanding at the student level, we must also foster chemistry understanding at the teacher level. This work has been relevant for my career as a pre-service teacher in that it has provided me with the opportunity to grow as both a learner and educator of chemistry. In this project, I had the opportunity to analyze chemistry teachers’ external representations of the chemical process of dissolution with respect to the depiction of bulk water.
Author: Emilia M. Kamis, Integrated Science Education Major
Faculty Advisors: Meng-Yang M. Wu; Ellen Yezierski, Chemistry and Biochemistry
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