Threshold Concepts in Chemistry: The Critical Role of Implicit Schemas

Abstract

Threshold concepts are conceived as cognitive portals to new and previously inaccessible ways of thinking in a domain. They are transformative, integrative, irreversible, and troublesome concepts that open the door to highly productive ways of thinking in a discipline. Mastering threshold concepts in chemistry demands the construction of diverse cognitive elements, including implicit schemas that guide and constrain how students think about chemical substances and processes. The central goal of this paper is to highlight five critical shifts in students' implicit schemas that should be fostered to support mastery of major threshold concepts in chemistry.

Uncovering Chemical Thinking in Students’ Decision Making: A Fuel-Choice Scenario

“…Participants at this level seemed to assume that bulk properties derive from the explicit properties of submicroscopic components and vice versa, which is consistent with previous studies. 27,33 In contrast, students who exhibited more advanced reasoning about the properties of substances tended to cue on implicit features in building explanations and making decisions. While the features they paid attention to were often inappropriate, the act of noticing these implicit characteristics of chemical entities (e.g., relative bond strength) seems to be a stepping stone in transitioning toward more sophisticated chemical thinking about how a substance's properties emerge from structural features.…”

“…Participants who expressed intuitive-relational reasoning about structure− property relationships to determine consequences of fuel usage commonly relied on an "additive framework" to think about chemical substances. 33 Within this framework, the properties of a chemical compound are thought of as the result of the weighted average of the properties of the compound's components (i.e., elements present in the compound, number and types of atoms that make up the substance, number and types of chemical bonds, etc.). For example, students often made associations between the properties of a given fuel and the presence of elemental components such as oxygen (e.g., more combustible because oxygen makes fire burn), carbon (e.g., more harm-causing because CO 2 , which damages the planet, contains carbon), and hydrogen (e.g., imparting waterlike properties to the fuel).…”

Understanding the uncomfortable kōkako: the challenge of applying threshold concepts in Māori studies

“…Barradell and Peseta (2014) noted that threshold concepts can be about more than just new ways of thinking, and can include changes in skills, attitudes and behaviours. Talanquer (2015:3) suggested a re-emphasis on "conceptual thresholds" to accentuate "the cognitive elements and processes that support the construction of a threshold concept and use the metaphor of "crossing a conceptual threshold" to signify the acquisition or development of such elements". Both suggest that the theory of threshold concepts can be further refined.…”

The Art & Science Project: Constructing Knowledge Through Creative Assessments

“…The assignment given to science students in the Art & Science Project requires them to choose a theme of interest in chemistry and to create a visual representation of it that portrays some of the nine core ideas in the field (Atkins, 2010;Talanquer, 2016), namely the atomic nature of matter, chemical bonds, periodic properties, molecular shape, intermolecular forces, types of chemical reactions, energy conservation, entropy, and barriers to reactions. By exploring these "big ideas" and the ways they interconnect, students can acquire deeper conceptual change by crossing threshold concepts (Meyer & Land, 2003;Talanquer, 2015), which are transformative, integrated, irreversible, and troublesome concepts that expand the disciplinary boundaries and the ways of thinking in a discipline.…”