Research in physical chemistry and chemical education: Part A: Water Mediated Chemistry of Oxidized Atmospheric Compounds Part B: The Development of Surveying Tools to Determine How Effective Laboratory Experiments Contribute to Student Conceptual Understanding.

摘要

This dissertation is a combination of two research areas, experimental physical chemistry, Chapters I to V, and chemical education, Chapters VI to VII.;Chapters I to V describe research on the water-mediated chemistry of oxidized atmospheric molecules and the impact that water has on the spectra of these environmental systems. The role of water in the Earth's atmosphere has been of considerable interest due to its ability to impact chemistry and climate. Oxidized atmospheric molecules in the presence of water have the ability to form hydrogen bonded water complexes. The spectroscopic investigation of nitric acid-water complexes, outlined in Chapter III, was undertaken to characterize intermolecular hydrogen bonds in a water-restricted environment at ambient temperatures. Additionally, this characterization of nitric acid-water complexes allowed for the comparison of calculated overtone OH-stretching vibrational band frequencies, intensities, and anharmonicities of intermolecular hydrogen-bonded water complexes with experimental observations.;Oxidized organic molecules, such as aldehydes and ketones, in addition to forming hydrogen-bonded water complexes can undergo a hydration reaction of the carbonyl group and form germinal diols in the presence of water. This chemistry has been studied extensively in bulk aqueous media, however little is known about this process in the gas-phase at low water concentrations. The focus of the studies outlined in Chapters IV and V is motivated by the ability of pyruvic acid and formaldehyde to form germinal diols and water complexes in water-restricted environment. This water-mediated chemistry changes the physical and chemical properties of these organic molecules, therefore, impacting the partitioning between gas and particle phase, as well as the chemistry and photochemistry of oxidized organic molecules in the Earth's atmosphere. The results presented in this dissertation may help resolve the significant discrepancy between atmospherically measured oxidized organic molecules and predictions of atmospheric models at different relative humidities.;The chemical education portion of this manuscript presented in Chapters VI and VII includes the development of a survey to determine how effective a laboratory experiment is in contributing to students' understanding of fundamental chemistry. The specific example used is an electrochemical cell. Our initial results showed that while most of our students could answer quantitative questions about the operation of the cell, their conceptual understanding of the microscopic processes that occur within the cell was inconsistent with the material presented in class. In particular, we noticed that while many students were able to correctly describe the events that take place at the surface of the anode and cathode, their understanding of the events that take place at the salt bridge was lacking.;In this investigation, we were able to confirm the misconceptions reported in previous studies. Our results suggest that a relatively modest, incremental revision of the experiment reduces these misconceptions and helped the students to develop a molecular-scale picture of the processes that occur within an electrochemical cell.