Session S40 (Tuesday, 9:30am, Thomas 215)

P386: Student ratio use and understanding of molarity concepts within solutions chemistry

Stephanie Ryan (University of Illinois – Chicago, USA)

In order to determine ways in which conceptions of ratio affected students’ understanding and use of ratio within solutions chemistry, data were collected using a structured interview approach. Grounded theory was used to analyze student responses with particular emphasis on ratio in molarity to develop theoretical statements. A ratio in this context is the idea of two measured quantities in relation to each other (e.g. density is measured in grams per milliliter). An example of a ratio within solutions chemistry is molarity, which is measured in moles per liter and represented by the capital letter, M. Results from this study indicate that most students do not have an intensive view of molarity and interpret M to mean moles. This caused students to have difficulty reasoning through the “different volume same molarity” task. Students were able to represent concentration as an intensive quantity qualitatively through the structurally similar tasks. Students in this study were successful proportional reasoning problem solvers in the direct proportion problems. Students attempted to use direct proportions for inverse relationships in chemistry problems which led to incorrect answers. Recommendations include explicit connections between molarity and the structurally similar tasks so that the intensive nature of molarity is emphasized.

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