analogies

Photochromic glue and spring decorations

The many colors of springtime can be illustrated with photochromic pigments in commercial products. These products include UV beads, and more recently, photochromic glue. The glue can be used as a photochromic paint for paper or even eggs. The resulting colorful, decorative objects can be used to illustrate chemical discussions of aspects of photochemistry.

Bubbly BBs and Vaccinated Mentos: Chemical Illustrations to Promote Public Health Measures

The authors revisit "flattening the curve" demonstrations published during 2020 to see how they could represent the impact of vaccinations on the COVID 19 battlefront. These demonstrations do not demonstrate the mechanisms of vaccines themselves, but are rather analogies to their potential effect on a population. In these analogies, gas production still represents illness, but this time people are represented by objects added to the solutions which either enable gas production (unvaccinated individuals) or do not enable gas production (vaccinated individuals). These simple experiments are best used as stand-alone demonstrations, and links to videos are included in this writeup.

Chemical Illustrations of Flattening the Curve

With the current global COVID-19 pandemic, there has been much discussion of “flattening the curve” by social distancing. These ideas can be demonstrated chemically, for example, by the iron-catalyzed decomposition of hydrogen peroxide to produce an oxygen gas foam. Decreased hydrogen peroxide concentrations, representing decreased human population concentrations from social distancing, produce oxygen gas foam, representing cases of illness, at a slower rate. A similar demonstration can be achieved using the popular Diet Coke and Mentos experiment. These simple experiments are best used as stand-alone demonstrations.

Equilibrium Snowball Fight

For dynamic equilibrium, I like to use a physical analogy that pits students against each other in a classroom-wide “snowball” fight. Not only is this activity great for building students’ conceptualization of dynamic equilibrium, it is also really fun!

Gibbs Free Energy Analogy

A common topic in chemistry discussion groups and forums is about the use of the terms “spontaneous reaction” versus “thermodynamic favorability”. This is a new activity for chemistry students who struggle with the correlation between changes in enthalpy, temperature, entropy, and the Gibbs free energy of a system; which relies on an analogy that most students will be familiar with.

Analogy Experiment—Projectile Pennies with Rutherford

Atomic theory is a common topic throughout any introductory chemistry course. It is likely that Rutherford’s gold foil experiment gets at least some attention in your course. I have used a simple activity that gives students an opportunity to replicate Rutherford’s experiment through an analogy experiment that may allow for easier conceptualization of the experiment itself and provide additional support for model development.