Classification of chemical reactions: Stages of expertise

In this study we explore the strategies that undergraduate and graduate chemistry students use when engaged in classification tasks involving symbolic and microscopic (particulate) representations of different chemical reactions. We were specifically interested in characterizing the basic features to which students pay attention when classifying chemical reaction at the symbolic and microscopic levels. We identified the categories that students create when classifying chemical reactions, and compared the performance in simple classification tasks of students with different levels of preparation in the discipline. Our results suggest that advanced levels of expertise in chemical classification do not necessarily evolve in a linear and continuous way with academic training; a significant proportion of undergraduate students, regardless of their preparation in chemistry, based their classification schemes on the identification of surface features and failed to create chemically meaningful classes. Students' ability to identify chemically meaningful groups was strongly influenced by their recent learning experiences and their graduate work in chemistry. The level of features used to build a class, and the role that these features played during the classification process. Although all of the participants in our study expressed similar levels of unfamiliarity with the microscopic chemical meaning. (C) 2007 Wiley periodicals, Inc.