Teaching and learning distillation in chemistry laboratory courses

Abstract

This study investigates the problems chemistry majors have with learning distillation in traditional chemistry laboratory courses. Using an interpretive cyclic research design, we collected and interpreted data, mainly in the form of observation notes and transcriptions of the discourse that takes place during laboratory courses. It was found that students experience numerous problems; these are described and interpreted. We summarize students' problems in four categories: (a) students use an independent component conception; (b) they have insufficient understanding of the properties of vapor; (c) they regard distillation from a physical point of view; and (d) they do not have a practical understanding of thermodynamics. The main origin of these problems was found to lie with the traditional curriculum structure. Lecture courses and textbooks treat distillation in a generalized and decontextualized way, whereas decisions in actual distillations are always based on contextual features. It was found that textbooks and teachers often do not discriminate carefully and explicitly among five different contexts for distillation: organic synthesis, chemical analysis, analytical chemistry, physical chemistry, and preparation of products. Students take the generalized concepts at face value and apply them to all distillations regardless of context. They cannot interpret their observations or make reasoned decisions based on the theoretical framework of a specific context.