Chemistry

The high-performance liquid chromatography (HPLC) experiment, most often done in the undergraduate analytical instrumentation laboratory course, generally illustrates reversed-phase chromatography using a commercial C18 silica column. To avoid the expense of periodic column replacement and introduce a choice of columns with different stationary phases, we have developed an experiment in which students prepare and test a polymer-based monolithic column. The 10 or 15 cm monolithic column is prepared using 1/8 in. o.d. × 2.3 mm i.d. poly(ether ether ketone) or PEEK tubing. The reaction is accomplished thermally at 60 °C for several hours by polymerization of butyl methacrylate cross-linked with ethylene glycol dimethacrylate in a porogen system consisting of 1,4-butanediol, 1-propanol, and water. Using toluene and naphthalene as analytes, profiles of retention factor as a function of methanol have been shown. A study of essential nutrients can be accomplished by using an ion-pairing reagent to separate thiamine from riboflavin. In addition, plate count and van Deemter plots can be done to determine column efficiency. The experiment can be designed to be completed over a 1 to 3 week period of time. Exposure to polymer chemistry, often not a part of the undergraduate laboratory curriculum, is an additional important aspect of this experiment.

The goal of this project was to create an inquiry activity to teach symmetry elements and symmetry operations in an inorganic chemistry course. Many students experience difficulty when building and mentally manipulating three-dimensional mental models from two-dimensional images, causing difficulty when learning symmetry. Process-oriented, guided-inquiry learning (POGIL) was used to structure the activity using a learning cycle paradigm consistent with research on how students learn as described by Novak’s human constructivism theory. The activity familiarized students with symmetry terms as students actively engaged in finding symmetry operations in a variety of molecules. The symmetry activity was classroom tested and student and POGIL expert feedback were used to improve the activity.

The central goal of this study was to create a new diagnostic tool to identify organic chemistry students’ alternative conceptions related to acid strength. Twenty years of research on secondary and college students’ conceptions about acids and bases has shown that these important concepts are difficult for students to apply to qualitative problem solving. Yet, few published studies document how students’ prior knowledge of acids influences their understanding of acid strength in organic chemistry contexts. We developed a nine-item multiple-tier, multiple-choice concept inventory to identify alternative conceptions that organic chemistry students hold about acid strength, to determine the prevalence of these conceptions, and to determine how strongly these conceptions bias student reasoning. We identified two significant alternative conceptions that organic chemistry students hold about acid strength. Students who answered items incorrectly were more confident about their answers than peers who answered items correctly, suggesting that after one semester of organic chemistry, students do not know what they do not know. Implications for the teaching of acid strength are discussed.