Visual chunking as a strategy for spatial thinking in STEM.

Working memory capacity is known to predict the performance of novices and experts on a variety of tasks found in STEM (Science, Technology, Engineering, and Mathematics). A common feature of STEM tasks is that they require the problem solver to encode and transform complex spatial information depicted in disciplinary representations that seemingly exceed the known capacity limits of visuospatial working memory. Understanding these limits and how visuospatial information is encoded and transformed differently by STEM learners presents new avenues for addressing the challenges students face while navigating STEM classes and degree programs. Here, we describe two studies that explore student accuracy at detecting color changes in visual stimuli from the discipline of chemistry. We demonstrate that both naive and novice chemistry students' encoding of visuospatial information is affected by how information is visually structured in "chunks" prevalent across chemistry representations. In both studies we show that students are more accurate at detecting color changes within chemistry-relevant chunks compared to changes that occur outside of them, but performance was not affected by the dimensionality of the structure (2D vs 3D) or the presence of redundancies in the visual representation. These studies support the hypothesis that strategies for chunking the spatial structure of information may be critical tools for transcending otherwise severely limited visuospatial capacity in the absence of expertise.

Sketching the Invisible to Predict the Visible: From Drawing to Modeling in Chemistry.

Sketching as a scientific practice goes beyond the simple act of inscribing diagrams onto paper. Scientists produce a wide range of representations through sketching, as it is tightly coupled to model-based reasoning. Chemists in particular make extensive use of sketches to reason about chemical phenomena and to communicate their ideas. However, the chemical sciences have a unique problem in that chemists deal with the unseen world of the atomic-molecular level. Using sketches, chemists strive to develop causal mechanisms that emerge from the structure and behavior of molecular-level entities, to explain observations of the macroscopic visible world. Interpreting these representations and constructing sketches of molecular-level processes is a crucial component of student learning in the modern chemistry classroom. Sketches also serve as an important component of assessment in the chemistry classroom as student sketches give insight into developing mental models, which allows instructors to observe how students are thinking about a process. In this paper we discuss how sketching can be used to promote such model-based reasoning in chemistry and discuss two case studies of curricular projects, CLUE and The Connected Chemistry Curriculum, that have demonstrated a benefit of this approach. We show how sketching activities can be centrally integrated into classroom norms to promote model-based reasoning both with and without component visualizations. Importantly, each of these projects deploys sketching in support of other types of inquiry activities, such as making predictions or depicting models to support a claim; sketching is not an isolated activity but is used as a tool to support model-based reasoning in the discipline.

Reactivity Controlling Factors for an Aromatic Carbon-Centered σ,σ,σ-Triradical: The 4,5,8-Tridehydroisoquinolinium Ion.

The chemical properties of the 4,5,8-tridehydroisoquinolinium ion (doublet ground state) and related mono- and biradicals were examined in the gas phase in a dual-cell Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. The triradical abstracted three hydrogen atoms in a consecutive manner from tetrahydrofuran (THF) and cyclohexane molecules; this demonstrates the presence of three reactive radical sites in this molecule. The high (calculated) electron affinity (EA=6.06 eV) at the radical sites makes the triradical more reactive than two related monoradicals, the 5- and 8-dehydroisoquinolinium ions (EA=4.87 and 5.06 eV, respectively), the reactivity of which is controlled predominantly by polar effects. Calculated triradical stabilization energies predict that the most reactive radical site in the triradical is not position C4, as expected based on the high EA of this radical site, but instead position C5. The latter radical site actually destabilizes the 4,8-biradical moiety, which is singlet coupled. Indeed, experimental reactivity studies show that the radical site at C5 reacts first. This explains why the triradical is not more reactive than the 4-dehydroisoquinolinium ion because the C5 site is the intrinsically least reactive of the three radical sites due to its low EA. Although both EA and spin-spin coupling play major roles in controlling the overall reactivity of the triradical, spin-spin coupling determines the relative reactivity of the three radical sites.