Hour-long structured interviews were conducted with 16 volunteer students from four undergraduate physical chemistry classes. Many student alternative conceptions and nonconceptions were expressed about important material covering equilibrium and thermodynamics. Twenty-nine of these were prevalent (present in Ͼ25% of the students.) The student conceptions expressed in their interviews were compared with those expressed by experts in textbooks and rated using a 6-point rubric. These ratings were averaged into a rating in each of four subjects and an overall rating. Correlation indices were computed. The "quality of student conception" rating was best predicted by an aggregated t score for the results on instructor-designed in-class exams. This result indicates that instructor's exams and grades do in fact demonstrate the level of a student's understanding of this course material.

Hour‐long structured interviews were conducted with 16 volunteer students from four undergraduate physical chemistry classes. Many student alternative conceptions and nonconceptions were expressed about important material covering equilibrium and thermodynamics. Twenty‐nine of these were prevalent (present in >25% of the students.) The student conceptions expressed in their interviews were compared with those expressed by experts in textbooks and rated using a 6‐point rubric. These ratings were averaged into a rating in each of four subjects and an overall rating. Correlation indices were computed. The “quality of student conception” rating was best predicted by an aggregated t score for the results on instructor‐designed in‐class exams. This result indicates that instructor's exams and grades do in fact demonstrate the level of a student's understanding of this course material. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 1151–1160, 1998.

Stereochemically active lone pairs of electrons play an important role in a diverse range of physical phenomena in many materials, ranging from semiconducting halide perovskites to thermochromic inorganic−organic hybrids. In this paper, we demonstrate the importance of the 6s 2 lone pair of Pb on the reversible thermochromic transition in the mixed-anion inorganic compound, PbVO 3 Cl. This 6s 2 stereochemically active lone pair results in subtle structural distortions upon heating while maintaining its overall orthorhombic structure. These distortions result in competing interactions with the Pb 6s 2 lone pair and ultimately, a pronounced change between yellow and red at ∼200 °C. X-ray diffraction analyses of PbVO 3 Cl demonstrate two-dimensional features in contrast to the three-dimensional network in isostructural BaVO 3 Cl. X-ray and neutron pair distribution function experiments reveal that Pb−O interatomic distances decrease upon heating, while Pb−Cl distances are only affected by thermal motion. X-ray photoelectron spectroscopy measurements provide experimental evidence of the presence of the 6s 2 lone pair at the valence band maximum, which are corroborated by first-principles calculations. The results demonstrate a broadly generalizable mechanism for using repulsions between lone-pair electrons of p-block cations to drive discontinuous changes of local symmetry and electronic structure.

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The physical chemistry course has long been known partially to "set the tone" of the chemistry major. It is, therefore, incumbent on the physical chemistry instructor to present this material in a manner that excites students, illustrates the usefulness of the material, and generates an understanding of the chemistry, rather than as a series of dull mathematical abstractions upon which the foundations of chemistry are laid. We believe that there are several indicators of whether this is being accomplished.