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R f values in thin-layer chromatography (TLC) depend strongly on solvent saturation of the atmosphere above the liquid in the TLC developing chamber. Although there are a multitude of experiments in the literature that describe the use of TLC for the analysis of a mixture, we were unable to find one in which the student discovers the importance of maintaining the solvent atmosphere during development of a TLC plate. The experiment reported here illustrates the potentially dramatic effects on TLC R f values of not equilibrating the solvent atmosphere during development.

The purpose of this communication is to describe and document the challenges of delivering a general chemistry laboratory experience to students and of moving toward multiple small assessments and away from high-stakes examinations. By leveraging of activities that were already in place prior to the pivot to online learning, namely, an electronic laboratory notebook through bluedoorlabs and assessments that emphasized student reasoning, these challenges were addressed. Herein our approach to providing a meaningful laboratory experience and lower-stakes assessments is described. On the basis of our experiences in Spring 2020, we look forward to the fall semester, where the university is committed to reopening in a dedensified fashion with students in classrooms and laboratories.

An understanding of buffers is important in a variety of chemistry subdisciplines, with relevant applications to the life sciences and health profession-related fields. Here, we describe the development and implementation of a lab that involves creating a buffer solution using baby wipes and deionized water. The goal of this lab was to emphasize a conceptual understanding of buffers within a context that would be interesting and relevant for students in a nonmajors general chemistry course, a population composed primarily of health/human science and agricultural science majors. The prelaboratory assignment and postlaboratory discussion focus on modeling by making connections between laboratory observations and the particulate-level view of a buffer. Overall, the experiment seeks to prompt students to think beyond the macroscopic view that buffers resist changes in pH and guide students toward thinking mechanistically about how a buffer resists changes in pH, a process that depends largely on the buffer components and their respective amounts.