Many studies in the chemical education literature report students' alternative conceptions in chemistry and the difficulty they present for future learning. In this paper, we review existing diagnostic tools used to uncover students' alternative conceptions in chemistry and suggest that there are two fundamental issues with such instruments, namely, the breadth of topics and concepts assessed and the reliance on forced choice responses. We argue that while existing instruments provide a way to assess students' overall understanding of chemical concepts, they cannot assess depth of understanding of any single concept, such as the particulate nature of matter -one of the central, organizing ideas in chemistry. Instead, we propose using qualitative approaches that utilize drawing tasks as an alternative diagnostic tool to uncover students' underlying struggles with fundamental chemistry concepts. Using this approach, we investigated college students' ability to balance chemical equations and draw appropriate particulate representations of those reactions. Emerging categories from students' particulate drawings were coded into several subcategories and revealed a number of underlying issues, such as lack of understanding of appropriate relationships between reacting species in solution, oxidation numbers, states and valences of species, the characteristics and nature of ions in solids and differences between ionic and covalent bonds. We describe these findings and consider the implications of qualitative-based diagnostics for instruction and science learning as a formative assessment tool.

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The goals of this study were (1) determine the prevalence of various features of representations in five general chemistry textbooks used in the United States, and (2) use cognitive load theory to draw implications of the various features of analyzed representations. We adapted the Graphical Analysis Protocol (GAP) to look at the type of representations used, the function of each representation, the physical integration of representations with associated text, the presence and nature of captions and labels, the indexing of representations, and the number of representations requiring conceptual integration on a given page. Results indicate that on average, in all five textbooks each page had at least four representations. Most representations served a 'representational' function, but a number functioned as decorative representations. Most representations were directly integrated with text, but some of the remaining representations were separated by a whole page from associated text. While many pages had an average of two representations that required conceptual integration with text or other representations, some pages had as many as six representations requiring integration. While using textbooks, learners can experience intrinsic, germane or extraneous cognitive load (Sweller, 1994). Our findings indicate that there are various features of representations that could help reduce intrinsic or extraneous cognitive load. However, we also found prevalent features of representations that imply high intrinsic cognitive load or are likely to lead to extraneous cognitive load. Implications for textbook authors and editors, textbook selection, instruction, and science teacher preparation are discussed.

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