Stoichiometry is regarded as a difficult topic in general chemistry, especially when students are presented with conceptual problems. Many general chemistry textbooks have end-of-chapter conceptual problems that assess students' understanding of stoichiometry through the use of pictures of differently sized and colored shapes representing atoms and molecules. However, little has been published about how students approach these problems. Therefore, students' evaluations of the accuracies of diagrams of differently sized and colored circles to represent various atoms in chemical reactions and their reasoning patterns were investigated. Based on the results of semi-structured interviews, an instrument was developed that asked students to first evaluate different representations based on: 1) ratios between reactants and products, 2) reaction yields, 3) number of excess reactants, and 4) correct choice of limiting reactant. Students were then asked to determine the accuracy of each diagram. First year students (N=1,126) from three different types of general chemistry courses participated in the study. A quantitative analysis of students' responses to the instrument as well as their implications for a future eye-tracking study will be presented.

Geometric representations of atoms and molecules and the pervasiveness of student misconceptions in chemical stoichiometry

247th National Meeting (2014)

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