James M. Nyachwaya

A qualitative report of the ways high school chemistry students attempt to represent a chemical reaction at the atomic/molecular level

We report the findings of a large-scale (n=1,337) qualitative descriptive analysis of U.S. high schools students’ particulate representations of a chemical reaction, specifically, the combustion of methane. Data were collected as part of an end of course exam. Student representations were coded into 17 distinct subcategories under one of five broad themes: i) Particulate Representations with discrete atoms, ii) Inappropriate Particulate Representations, iii) Quasi-particulate Representations, iv) Non-particulate Representations, or v) Irrelevant Attempts. Only 35.1% of student responses showed representations with discrete atoms that appropriately matched the individual molecular formulas in the combustion reaction. Of student responses, 45% were representations with discrete atoms; however, these representations were not chemically appropriate, displaying either incorrect connections between atoms within individual molecules or inappropriate groupings of atoms into individual molecules. 5.9% of student responses were coded as quasi-particulate, and included representations that displayed some form of particles that did not show discrete atoms. 22.9% of student responses were coded as non-particulate. The remaining 5.5% of responses represented no real attempt to address the question. The various representations are illustrated and described to provide a map of the domain of students’ alternative conceptions of chemical reactions. Interestingly, of the 65% of students who were able to balance the equation correctly, more than half were unable to show the appropriate particulate representation. The ability to represent a chemical reaction at the symbolic level does not guarantee the ability to represent the reaction at the particulate level.

College chemistry students' use of memorized algorithms in chemical reactions

This study sought to uncover memorized algorithms and procedures that students relied on in responding to questions based on the particulate nature of matter (PNM). We describe various memorized algorithms or processes used by students. In the study, students were asked to balance three equations of chemical reaction and then draw particulate representations of the compounds in the reactions. Students were then interviewed to uncover their understanding of underlying chemistry, taking note of any memorized algorithms that students were using. In addition to specific algorithms that students used, two trends were apparent from our analysis: (1) students successfully applied algorithms (in operations such as equation balancing) without necessarily understanding why they used the particular operations or processes. (2) Students have memorized processes and ideas which they incorrectly applied. Implications for assessment, research and instruction are also suggested.

Features of representations in general chemistry textbooks: a peek through the lens of the cognitive load theory

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) (Slough et al., 2010) 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.