In the studies reported here, we investigate the effects of context on students' molecular-level ideas regarding aqueous solutions. During one-on-one interviews, 19 general chemistry students recruited from a two-year community college and a research university in the United States were asked to describe their molecular-level ideas about various aqueous solutions in the contexts of conductivity and boiling-point (BP) elevation. Results indicate that context is important for determining the molecular-level ideas that students express. Specifically, students were significantly more likely to draw pictures of aqueous NaCl as separated ions in the conductivity context compared with the BP elevation context, for which they more often drew "molecular" NaCl. This phenomenon was particularly striking because the students drew molecular-level NaCl(aq) pictures in the BP elevation context just minutes after completing the identical task in the context of conductivity. Additional data from laboratory assignments and course examinations further indicate that, even if students are able to correctly represent the molecular level in some contexts, their knowledge may remain inert in slightly different contexts. The results emphasise the importance of the context dependence of molecular-level ideas and have implications for designing instruction in which students develop robust, coherent understandings that they can apply appropriately in new contexts.
This study investigated relationships
between the thinking processes
that 28 undergraduate chemistry students engaged in during guided
discovery and their subsequent success at reasoning through a transfer
problem during an end-of-semester interview. During a guided-discovery
laboratory module, students were prompted to use words, pictures,
and symbols to make their mental models of chemical compounds added
to water explicit, both prior to the start (initial model) and at the end (refined model) of the module.
Based on their responses to these model assignments, we characterized
students’ knowledge and thinking processes, including the extent
to which individual students engaged in (a) constructing
molecular-level models that were consistent with experimental evidence; (b) constructing molecular-level models that
progressed toward scientific accuracy; (c) constructing molecular-level models that were scientifically correct; (d)
making connections between laboratory observations and the molecular-level
behavior of particles; (e) accurate metacognitive monitoring of how their
molecular-level models changed; and (f) using evidence to justify model
refinements. Analyses revealed three thinking processes that were
strongly associated with correct reasoning in the transfer context
during an end-of-semester interview: constructing molecular-level
models that were consistent with experimental evidence, engaging in
accurate metacognitive monitoring, and using evidence to justify model
refinements. The extent of student engagement in these three key thinking
processes predicted correct reasoning in a new context better than
the scientific correctness of a student’s content knowledge
prior to instruction. Although we did not explore causal relationships,
these results suggest that integrating activities that promote the
key thinking processes identified into instruction may improve students’
understanding and success at transfer.
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