Progression toward Causal Mechanistic Reasoning through Phenomenon-Based Learning in Introductory Chemistry

Abstract

The alignment of teaching and assessment in chemistry courses is critical for the practice of science and positive student learning outcomes. This paper addresses how instructors can align what they do in class with assessments across topics to improve students' understanding and explanations of chemical phenomena. We drew on the foundations of Phenomenon-Based Learning to introduce how observable events can be used as an entry point into causal mechanistic reasoning, an essential explanatory practice for scientists. This cross-institutional study focuses on two chemical phenomena: dissolution and boiling point. Students from three different learning environments completed phenomenon-based tasks centered on these two phenomena, and their responses were analyzed for different levels of causal mechanistic reasoning. We then analyzed instructors' dialogue for evidence of causal mechanistic reasoning from content units where these phenomena were emphasized. Using students' responses to the tasks and the instructor dialogue from the content units, we observed students activating more resources related to particulate behaviors when explaining the focal phenomena after instruction emphasized using causal mechanistic reasoning to explain phenomena. This is noteworthy, as it highlights the promise of sustained phenomenondriven curricula by helping students explain events using deeper levels of reasoning. Our work provides evidence for instructional and curriculum developers to design courses in a way where we are demonstrating to students what practicing scientists do. We discuss implications for practitioners that include ways to use observable events and chemical phenomena as a foundation to promote causal mechanistic reasoning in chemistry.

How We Simplify, Circumvent, or Distort Causal Mechanistic Reasoning in Chemistry

“…The approaches used to simplify or circumvent MER often involve mechanisms that explain how structural differences or changes affect the relative stability of the entities involved. Research in chemistry education shows that novice students often struggle to build such connections but possess cognitive resources that can be leveraged to foster their MER abilities. ,− For example, student understanding can be strengthened by properly using educational resources such as tutorial videos and animations , that facilitate the unpacking of mechanistic relationships. Designing and engaging students in carefully scaffolded tasks that provide a stepwise structure to guide their thinking also support the development of MER. , It is also important to make more explicit to students the concepts we encapsulate, the associations we build, and the simplifications we make, as it opens spaces for students to practice and metacognitively reflect on their abilities to unpack the underlying mechanisms .…”

“…Nevertheless, “the dose makes the poison”. Abusing the use of these types of reasoning shortcuts without creating opportunities for students to (a) build the associated canonical mechanistic explanations, (b) compare and contrast the different types of rationales that we generate in chemistry, , and (c) reflect on their strengths and limitations is likely to shortchange students’ ability to apply chemical thinking in effective and productive ways across different contexts.…”