“’Yes, as Ma would say, enough is as good as a feast,’ Laura agreed.”
Laura Ingalls Wilder’s Little House book series jumps back onto my “to read” list roughly once a year. These Happy Golden Years is one of my favorites from the collection, and the above quote from its pages sprang to mind as I read the October 2017 issue of the Journal of Chemical Education.
The article that spurred the thought was one that appealed to me because of its simplicity, its use of items that one could easily find already in the lab or in local stores, and its connection to typical topics students encounter early on in a first chemistry course. Although the lab itself is easily taken on by students new to chemistry—“enough”, the resulting richness of learning outcomes provides the “feast.”
In Hydration of Decorative Beads: An Exercise in Measurement, Calculations, and Graphical Analysis by Hill and Nicholson (available to JCE subscribers), students hydrate small spheres made of superabsorbent polymers. I’ve had luck finding them at craft stores such as Jo-Ann Fabric (use one of their often available online coupons) in the floral department, sold in small bags as “water gems.” The authors suggest coloring the dehydrated clear and colorless spheres with permanent markers so they are easily visible in water, but they can also be purchased in a variety of colors.
JCE Abstract Figure – Reprinted with permission from Hydration of Decorative Beads: An Exercise in Measurement, Calculations, and Graphical Analysis. Rebecca A. Hill and Christopher P. Nicholson. Journal of Chemical Education, 94 (10), 1517-1521. Copyright 2017 American Chemical Society.
Students begin with a comparison of different ways to measure water volume using devices with different levels of accuracy. They then collect mass and volume data for dehydrated spheres. After an assigned amount of hydration time in a hot water bath, the spheres are remeasured. A variety of heating times are assigned, so the class data set can later be used for graphical analysis practice. While the idea is simple, the list of skills that students practice is long—measuring liquid volumes, measuring masses, calculating the volume of a sphere, calculating an average, calculating standard deviation, using significant figures, and generating a graph of data with a spreadsheet program.
I liked the opportunity for students to consider reasons why variations arise in the data when comparing their results to others in class. The authors mention a few possibilities, such as not removing drops of water from the spheres before weighing, along with the fact that some of the spheres hydrate somewhat oddly, making volume calculations difficult. It's also a low waste lab. The spheres can be reused if they are not damaged while hydrated. Or, the hydrated spheres can be crushed into smaller pieces and used in potted plants or gardens.
Once you have the polymer spheres, you can also use them for other activities. I have done make-and-take outreach where students compare spheres before and after hydration, observing beads placed in snack-size zip-seal plastic bags. They then scoop a cup of hydrated spheres and add a seed—will the seed eventually germinate? What makes the spheres useful for germination? I also recently saw a video of the spheres heated in a hot pan to show a Leidenfrost effect that I would like to recreate.
More from the October 2017 Issue
Mary Saecker collects the rest of the issue in her JCE 94.10 October 2017 Issue Highlights, including multiple items for National Chemistry Week 2017, with its geology theme “Chemistry Rocks!”
How have you used Journal resources? We want to hear! Start by submitting a contribution form, explaining you would 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.