Students' Understanding of Energy in Chemical Reactions and Processes

Kinsey Bain, Purdue University

Abstract

In this study students were interviewed in order to elicit their understanding of energy in chemical reactions and processes. Previous work has demonstrated that energy concepts are abstract and difficult to understand and describe for students across secondary, tertiary, and graduate levels. Using an interview-about-events protocol, semi-structured interviews with introductory-level undergraduate chemistry students, upper-level undergraduate chemistry students, and physical chemistry graduate students were conducted in order to investigate participant understanding of energy in chemical reactions and processes. This study was designed to lay the groundwork for the eventual development of an energy learning progression for implementation in a general chemistry course. Content analysis was conducted using the general chemistry anchoring concepts content map (ACCM), supplemented by open coding. This revealed that students most commonly discussed ideas relating to the anchoring concepts of energy, reactions, bonding, visualization, and intermolecular interactions. Specific concepts included ideas like heat exchange (as measured via temperature change), Gibbs free energy (as it relates to enthalpy and entropy changes), entropy, the energetic nature of bonding, and the definition and nature of heat. Other ideas discussed that were not a part of the ACCM were the definition of temperature, spontaneity (as an idea that was distinct from Gibbs free energy), and the definition of energy (as a broad concept). Alternative conceptions and uncertainty/unfamiliarity with content were also coded. Each participant expressed an alternative conception at some point during their interview, though the relative occurrence varied across participant levels. Common alternative conceptions included the determination of what happened/what products formed, the energetic nature of bonding, temperature, entropy, and Gibbs free energy. Introductory-level undergraduate students demonstrated difficulty defining heat, as well as the system and surroundings. They also more frequently reported being uncertain about or unfamiliar with many concepts when compared to the more advanced students as well. Upper-level undergraduate students showed that they had a greater breadth of energy content to consider in chemical reactions and processes when compared to the introductory-level students. This group of students retained some of the common alternative conceptions that introductory-level students held, while also revealing new alternative conceptions. Graduate-level students were unique in that, while they did demonstrate a small amount of alternative conceptions, they often were able to correct themselves as they continued in their interviews. A second round of coding was conducted to analyze student reasoning about energy in chemical reactions and processes, revealing emergent themes of reasoning with respect to both content and student level. There were distinct modes of reasoning expressed by students with respect to enthalpy, entropy, and Gibbs free energy. There were also distinct modes of reasoning expressed by students at different levels. Introductory-level students utilized teleological reasoning, had difficulty explain why reactions happened, expressed intuitive ideas of spontaneity, and believed observed temperature changes signaled that a reaction must have occurred. Upper-level students also utilized teleological reasoning; however, they did not express intuitive ideas about spontaneity. They often replaced them with conflated ideas about enthalpy and Gibbs free energy/spontaneity. Graduate-level students typically demonstrated scientifically correct understanding and reasoning. If they did use heuristic reasoning, they could also demonstrate more sophisticated reasoning as well. Each of these patterns was categorized according to a methodological framework to provide insight into student reasoning and implications for instruction and curricula. Implications of this dissertation for research and practice are also discussed.

Degree

Ph.D.

Advisors

Towns, Purdue University.

Subject Area

Chemistry

COinS