This study investigates how students account for a macroscopic temperature change during the dissolution of ionic salts through particulate level explanations. Semi-structured interviews were conducted with general chemistry, physical chemistry, and biophysical chemistry students. During the interviews, students conducted hands-on tasks that included the touching of beakers containing exothermic or endothermic dissolution processes. Data analysis resulted in categorizing students into groups based on their ideas about bond breaking, bond making, and energy changes. Students’ particulate understandings of the dissolving process did not appear to impact their explanations of the energy changes they observed. Only two students (one from general chemistry and one from biophysical chemistry) correctly described both the dissolving process and the macroscopic energy changes. No students invoked the concepts of potential energy, lattice energy, or enthalpy of hydration to explain their observations.
Learning thermodynamics requires understanding abstract topics such as entropy and spontaneity. Students tend to rely on metaphors and everyday meanings to reason about these topics. This study investigates how students explain dissolution and precipitation using the concepts of entropy and spontaneity. Students from general chemistry, physical chemistry, and biophysical chemistry participated in semistructured interviews. During these interviews, students observed four tasks: an exothermic dissolving process, an endothermic dissolving process, the insolubility of an ionic salt, and a precipitation reaction. Students reasoned about their observations of dissolving, insolubility, and precipitation by describing entropy as the disorder of a chemical system and describing disorder in several different ways. Few students mentioned microstates or the distribution of energy. Students determined which of the four tasks were spontaneous and offered explanations that included reasoning about changes in enthalpy, reasoning about changes in entropy, and/or using concepts from kinetics. Students’ ideas about entropy changes and spontaneity are examined, and the implications for classroom teaching and future research are discussed.
The Enthalpy and Entropy in Dissolution and Precipitation Inventory (E 2 DPI) has been developed to measure student understanding of the dissolution of ionic solutes, aqueous precipitation reactions, and the enthalpy and entropy changes that accompany these processes. The E 2 DPI was designed using a mixed-methods protocol, such that the questions on the instrument were grounded in the reasoning and explanations offered during the semi-structured interviews with general chemistry and physical chemistry students. The concept inventory was administered to general chemistry (n = 383), physical chemistry (n = 10), and biophysical chemistry students (n = 43) at one institution. The inventory was also administered at a second institution to students in a postorganic General Chemistry II course (n = 160). The validity and reliability of the data generated from the E 2 DPI were assessed using both qualitative and quantitative data. Some of the misconceptions assessed by the instrument and data indicating the prevalence of these ideas are presented.
The effective use of formative assessment (FA) has been demonstrated to confer positive impacts on student learning. To understand why and how FA works, it is necessary to characterize teachers' FA practices, but because both teaching practice and learning depend on the nature of the discipline, there are disciplinary aspects to examining this. This study aimed to develop an analysis of chemistry teachers' FA practices through the lens of the chemical thinking framework. Two cohorts of middle and high school science teachers participated in year-long professional development with the goal of improving their FA practices in teaching chemistry. Each teacher submitted FA portfolio chapters throughout the year. To develop an approach to use in ongoing research that will analyze teachers' progress across the year, the final FA portfolio chapters of participants (N = 13) were analyzed to characterize FA task design, the teacher's purpose in implementing the FA, and how the teacher evaluated student work. FA tasks were found to range from revealing students' mastery of concepts to uncovering students' chemical thinking. Teachers also demonstrated a range of purposes behind their use of the FA tasks, and a range of focuses when evaluating student work. Correspondence among the FA task, a teacher's purpose for its use, and the teacher's evaluation approach revealed patterns that echo the broader research in science education, but with instantiation in chemistry. Ways for teachers to assess and diversify their own FA practices based on these findings are presented.
A structured inquiry experiment for inorganic synthesis has been developed to introduce undergraduate students to advanced spectroscopic techniques including paramagnetic nuclear magnetic resonance and electron paramagnetic resonance. Students synthesize multiple complexes with unknown first row transition metals and identify the unknown metals by correlating spectroscopic data to electronic structure. Students are assessed through an oral presentation of their spectral analyses and conclusions. Data are included in Supporting Information for institutions without access to an EPR.
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