Polymers and Cross-Linking: A CORE Experiment To Help Students Think on the Submicroscopic Level

摘要

The Polymers and Cross-Linking experiment is presented via a new three phase learning cycle: CORE (Chemical Observations, Representations, Experimentation), which is designed to model productive chemical inquiry and to promote a deeper understanding about the chemistry operating at the submicroscopic level. The experiment is built on two familiar activities often used in public outreach: mixing solutions of poly(vinyl alcohol) and sodium borate, producing the substance known as "slime", and linking paper clips as an analogy to represent polymers. In phase 1 of the CORE experiment, students prepare slime, and explore the properties of the separate solutions and slime. In phase 2, students use analogical reasoning to think about a representation for considering the chemistry at the submicroscopic level. The analogy activity includes using an Analog to Target Worksheet to carefully consider similarities and differences between the analog (paper clip chains) and target (polymers). Phase 3 begins with pairs of students designing experiments in response to this question: How do different proportions of the two reactants, poly(vinyl alcohol) and sodium borate, affect the material properties of the new polymer that is formed? In a recent JCE paper, we report the capacity for students to engage in using analogical reasoning when conducting the Polymer and Cross-Linking experiment. In this paper, we include an analysis of a postlab question, asking students to propose an alternative analogy that could be used in the lab experiment. Detailed analysis of a subset (23 out of 312) of student-generated alternative analogies is provided in Supporting Information. Together with the previously published paper, the data provides insight into student thinking about using analogical reasoning in the Polymers and Cross-Linking CORE experiment.