Chemical representational competences : a qualitative study on Hong Kong secondary student learning of covalent bonding, structures and properties

Abstract

Chemical representational competencies (CRC) are fundamental competencies in chemistry. Extensive studies have discussed the significance of representational competencies in science, particularly in chemistry, and proposed various strategies or tools to enhance different aspects of CRC. However, students’ abilities and the difficulties that they may encounter in dealing with various chemical representations in learning chemistry are yet to be fully explored.

Firstly, this thesis introduces three models of representational competencies, namely, metavisualisation, metarepresentational competence and representational competence. Based on the curriculum requirement and textbook analyses of the structures and properties of covalent substances in the Hong Kong senior secondary chemistry curriculum, five representational competencies are identified and selected from the three models of representational competencies to develop the CRC model. These dimensions are (a) recognising chemical representations, (b) translating chemical representations, (c) identifying the differences between chemical representations and the concepts that they represent, (d) applying chemical representations in solving problems and (e) learning new chemical representations. Then, based on the literature, levels for each dimension of CRC are developed and used to analyse students’ competencies and their difficulties. To investigate students’ CRC in depth, this small-scale qualitative study was conducted. Two CRC written instruments were designed and administrated to a class of students who took senior secondary chemistry in Hong Kong in February 2016. Six students were selected for an interview. They were asked to elaborate on their responses to the instruments. All of the verbal and written responses, drawings and gestures were recorded, transcribed and analysed according to each dimension of CRC and the levels within each dimension.

This study has two major findings. Firstly, five dimensions of CRC are indispensable to students’ learning of the structures and properties of covalent substances. They are independent competencies but are related in many ways. For example, the translation of chemical representations is inseparable from students’ understanding of the submicroscopic structures of covalent substances. Moreover, the translation of chemical representations is informed by recognising the provided representation and enhances students’ recognition of the provided representation. Secondly, the difficulties that students may encounter with their CRC are identified. For example, students’ ideas about colours as a representation of temperatures that they acquired from physics are observed to have a negative influence on their learning of electron density diagrams.

This study has both theoretical and practical implications and significance. Theoretically, this research discusses the five dimensions of CRC needed in the context of the topic of the structures and properties of covalent substances and provides a comprehensive understanding of different levels of students’ CRC. These findings enrich the theory of representational competencies in science and shed light on further research on representational competencies in other science subjects. This study reveals to teachers, textbook authors and curriculum developers that they should pay attention to the difficulties that students may encounter with their CRC. Finally, we should acknowledge that these five dimensions of CRC are discussed in the context of this topic only. Thus, further studies of CRC in other topics are needed.