"See it today—use it tomorrow" was the tagline. It was one of my favorite workshops to lead, now a decade ago. I highlighted several JCE Classroom Activities that were easy to prep quickly, with materials found around the house. They were good for using with little or no notice, like an unplanned sub. Even now, these same types of articles are some of first to catch my eye in new issues of the Journal of Chemical Education. This month, it was Polymer Processing Demonstrations Using PET Bottles (available to JCE subscribers, and ACS or AACT members)*.
In the article, Mateus describes three demonstrations he used in a high school level environmental chemistry class. The second and third fit my criteria of fast and easy, with materials I already had on hand. The one titled "Plastics Don't Forget" set me in motion. First, the recycling bin for a discarded soda bottle. Next, a few minutes in the garage with a saw to cut off the threaded top (plus grab the pliers). Then to the kitchen stove to heat water. I saw it. I tried it. I could use it tomorrow in a classroom. His figure below shows the steps. Students may be surprised to see the end result. What might seem permanently deformed returns to a circular shape, by just placing it in hot water again. When I tried it, it did take more than "a few seconds in the hot water" as the author states, but it eventually made its way back to circular. I also took it a step further and screwed the cap back on the threads after it cooled, to further show myself that it went back to its earlier shape.
Figure 2: Reprinted with permission from Polymer Processing Demonstrations Using PET Bottles, Alfredo Luis M. L. Mateus. Journal of Chemical Education, 96 (8), 1696-1700. Copyright 2019 American Chemical Society. "Plastics Don’t Forget demonstration. The threaded part of the bottle is heated in boiling water (a) and stretched with pliers (b,c). When the plastic piece is cooled, it remains stretched (d), but when it is placed back in hot water, it returns to its original shape (e,f)."
The bottom part of the bottle can also serve as the raw material for an additional demonstration from the article, "Making Spirals." Cut the bottle into a long strip, spiraling around the bottle as you go, then wrap the strip around a pipe and secure the ends. What do students predict will happen if it's submerged in boiling water, then cooled? What if the cooled piece were placed in a container of hot water again?
The author describes how he integrated it into the course:
"In the first part of the class, the role of chemistry in the production of materials that are used to manufacture almost everything that we use in our daily lives and the impacts of these processes on the environment are discussed. Concepts like product life-cycle analysis, green chemistry, and sustainable development are discussed in several activities. The chemical processes involved in the production of polymers, paper, cements, and metals like steel and aluminum are researched by the students. Afterward, a series of experiments and demonstrations like the ones described here are conducted with each of the materials to give the students a better grasp of the materials' properties."
Polymers are everywhere. Students use them, but may not have considered their specific properties. You've seen these today. They're an easy option for your toolbox of tomorrow.
More from the August 2019 Issue
This issue keeps the polymer idea rolling with Polymers, Giant Molecules with Properties: An Entertaining Activity Introducing Polymers to Young Students. You won't necessarily have the materials lurking in your house (sodium alginate and superabsorbent polymers), but they can extend a polymer unit.
Do you integrate polymers into your already packed curriculum? We'd love to hear how! Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.