450 Chem. Educ. Res. Pract., 2013, 14, 450--467 This journal is c The Royal Society of Chemistry 2013 Cite this: Chem. Educ. Res. Pract., 2013, 14, 450 Students’ understanding of the nature of matter and chemical reactions – a longitudinal study of conceptual restructuring Anne Bergliot Øyehaug* and Anne Holt This longitudinal study aims to provide greater insight into how students’ understanding of matter and chemical reactions develops over time and how their knowledge structures are restructured. Four case-study students in a Norwegian primary school were followed for two years from age 10–11 to age 12–13. Researchers were responsible for implementation of science teaching promoting systematic development of students’ understanding of the nature of matter and chemical reactions in many contexts across science disciplines. The four case-study students’ expressed understanding was recorded and analyzed throughout the period. Results indicate that students develop fragmented and incom- plete understanding, and drawing wrong conclusions may be necessary steps in the learning process. Moreover, students seem to develop a somewhat more integrated and cohesive understanding of the nature of matter and chemical reactions, indicating that the students restructure and reorganize their knowledge structures (i.e. differentiation, coalescence and promoting). Introduction Several groups have conducted longitudinal research investigat- ing how students conceive the particulate nature of matter and how their conceptual learning of these concepts progresses in a school environment (Johnson, 1998; Smith et al., 2006; Stevens et al., 2007; Adbo and Taber, 2009). Research shows that students who learn about atomic and molecular theory do it gradually (Arzi, 1988; Johnson, 2000, 2002). It takes a long time and great intellectual effort to build such abstract understand- ing. Meheut and Chomat (1990) found that if the curriculum and instruction focus on the essentials of atomic and molecular theory, students can use this to explain macroscopic properties. They suggest that students often change a whole set of concepts as they learn about the atomic and molecular theory. In addition, it seems to take a long time and great intellectual effort to build an understanding of matter at macroscopic and sub-microscopic levels. Some studies have taken a special interest in the long- itudinal perspectives of building an understanding of matter. Based on a study on the properties of substances, Eskilsson and Hellde ´n (2003) recommend introducing basic models in early science instruction, using students’ own ideas when talking about gases and everyday phenomena that deal with changes of substances. Johnson (2002) found that atomic and molecular theory is central for students to gain an understanding of chemical changes. Thus it seems as if having sub-microscopic ideas is essential for developing a deep understanding of the nature of matter and chemical changes, and that conceptual change is gradual. diSessa et al. (2004) and Hunt and Minstrell (1994) have also suggested that conceptual change is gradual and that students in addition hold intuitive ideas alongside instructed ideas. The present study aims to provide greater insight into how students’ understanding of matter and chemical reactions develops over time and to what extent their knowledge struc- tures can be characterized as knowledge-as-elements. Research questions in this study are: How do students’ conceptions of matter and chemical reactions develop when students are introduced to these con- cepts in different contexts and in increasingly complex ways? What characterizes students’ understanding in different phases of their actual learning trajectory? A theoretical framework for conceptual restructuring The analysis and discussion in this paper are conducted primarily from a so-called conceptual restructuring perspective, but considers ideas from additional perspectives as well. The term conceptual restructuring relates most directly to knowledge- as-elements perspectives. Knowledge-as-elements perspectives Faculty of Education and Natural Sciences, Hedmark University College, Norway. E-mail: anne.oyehaug@hihm.no; Fax: +47 6251 7601; Tel: +47 5271 7873 Received 15th February 2013, Accepted 7th May 2013 DOI: 10.1039/c3rp00027c www.rsc.org/cerp Chemistry Education Research and Practice PAPER Published on 06 June 2013. Downloaded on 01/03/2014 09:19:52. View Article Online View Journal | View Issue