Session: Undergraduate Research Posters: Chemistry Education:

The construction of explanations characterizes scientific behavior, and this process takes a central role in the advancement of science and technology. Scientific skills must come into play to generate causal relationships between empirical evidence and scientific theories to produce rigorous explanations. The work herein presents a learning experience centralized on the construction of explanations intended for chemistry teaching laboratories. In the lab, students studied a ternary system and its equilibrium state when the chemicals were mixed. The mixture’s chemicals were potassium carbonate (K₂CO₃), water, and isopropanol at different mass proportions. It was found that the value of the equilibrium constant (K_d) changed when the mass proportions of the species changed. The K_d was affected by the total number of molecules of each species present in the mixture. Students did not expect this result. Thus they needed to construct an explanation for the empirical data. To understand the dependency of K_d with the composition of the total mixture, students then studied the effect of temperature on the equilibrium state via the van’t Hoff isochore equation while also changing the overall mass composition of the species in the mixture. The resulting data allowed the calculation of the enthalpy change (ΔH) and entropy change (ΔS) for the separation process under the studied temperature range. With the values of ΔH and ΔS, students then worked on building causal relationships regarding intermolecular interactions and the changes in molar volume, leading to establishing the equilibrium state. Examples of procedures, data, and results will be presented and discussed to showcase the feasibility of the learning experience for chemistry laboratory programs.

Jacqueline Jimenez

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