Especially JCE: August 2017

Cover of August 2017 issue of JCE

Reading about a new idea for the classroom can sometimes spark connections to ideas that you already have in your teaching toolbox. The August 2017 issue of the Journal of Chemical Education triggered potential links for me—like stringing beads in a row.

In this case the beads were literal, from the article Using Beads and Divided Containers To Study Kinetic and Equilibrium Isotope Effects in the Laboratory and in the Classroom (available to subscribers) by Campbell, et al. Rather than beads with holes, the suggested materials are actually collections of “airsoft” pellets of two different weights, small plastic spheres that you can purchase in sporting goods departments, along with plastic Petri dishes. You modify a dish’s divider, then use it as a “shaker” as you observe how many of the pellets move from one side to the other to show reaction progress. Shaking can be slower, to represent a lower temperature, or faster, for a higher temperature.

Based on the title and abstract, this isn’t something that I would have thought to integrate into a high school classroom, since as the authors state, “Kinetic and equilibrium isotope effects are typically covered in upper-level courses in the chemistry curriculum.” It would be just one more thing to cram into an already packed schedule. But, the piece does adapt its visual pellet model to also illustrate the different activation energies when a reaction is catalyzed vs. uncatalyzed, which I would be more likely to use.

The authors do suggest that the isotope effect activity could be used at less advanced levels and offer ideas for doing so. The handouts included in the online supporting information provide clear background information about isotope effects and how they relate to the environment—connections that show students how chemistry is actually used to figure things out on our planet and beyond. The article describes how to use the models “to illustrate how water isotopic distributions can be used to estimate how the earth’s temperature has varied over time” as well as “to explain the history behind some of the current conditions on the surface of Mars.” It also has an intriguing idea for using multiple shakers at an outreach event to make a model that represents ice layers that could form over the years as ocean temperatures change.

Adding a Bead to the String

The association of beads and kinetics in the title brought to mind one of the JCE Classroom Activities that I most enjoyed testing and using with workshop groups: Putting UV-Sensitive Beads to the Test by Terre Trupp, a high school teacher (available to subscribers). It uses UV beads that appear white under regular light conditions, but turn a different color when exposed to UV light, and begins by baking them in the oven to flatten them into small disks. One part of the activity focuses on how temperature affects their color change. The results usually surprised participants, who predicted that disks placed over hot water would change color more quickly and have a deeper color. It is actually the opposite, with those results seen using cold water. A final portion of the activity uses the disks to test the effectiveness of various sunscreens, a real world connection. Over the years I’ve switched from swabbing the sunscreen on the disks directly, which makes it more difficult to check for a color change, to placing the beads in a zip-seal plastic bag, laying it flat, then spreading or spraying the sunscreen on the outside top of the bag. Students can then peek inside the bag, leaving it flat, to observe the resulting color.

One More Bead

Still loving the idea of using beads to illustrate chemistry concepts? Bring them into a unit on acids and bases. High school teacher Alice Putti describes the use of beads in Petri dishes to teach the concepts of ionization of strong vs. weak acids and diprotic vs. monoprotic acids in JCE Classroom Activity #109: My Acid Can Beat Up Your Acid (available to subscribers). Once again, the beads are easy to find, using pony beads from craft stores to make models that will last for repeated use over the years.

More from the August 2017 Issue

Mary Saecker collects the rest of the issue in her JCE 94.08 August 2017 Issue Highlights. There are multiple articles related to the environment and climate change.

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