The color of a thermochromic system depends on its temperature. The colors of leuco dye-based systems can also be influenced by adding acids or bases to the thermochromic reactions. These can be used to create colorful demonstrations of acid-base chemistry. Thermochromism found in color changing cups can also be used to visualize heat flow, and therefore thermodynamic principles, associated with stretching and contracting elastomers.
Placing dry ice in limewater is a great demonstration to accompany discussions on a variety of chemical topics, including the impact of ocean acidification on marine organisms that depend upon the formation of CaCO3.
Dean Campbell tries to use at least one demo for every class to illustrate concepts described in his chemistry courses. In this post, he includes short descriptions of the demonstrations and props he has used while teaching his collegiate General Chemistry II courses.
In a classic demonstration of energy conservation, smashing two large steel ball bearings generates sufficient heat to burn a hole through a piece of paper. Josh Kenney found this demonstration underwhelming because the paper doesn't look burned. So, he upgraded the experiment by covering the paper in Elmer's Color Changing Glue. Now, a spectacular color change reveals the increase in heat!
Learn a bit about the chemical reactions that occur during a lightning strike, and how you can demonstrate these reactions in your classroom.
Did you know that sand can be converted into a mixture of gases that spontaneously ignites in air? The procedures involved are relatively simple to perform, spectacular to observe, and relate to a rich assortment of chemical principles.
Learn a simple way to relate the heat equation (Q = mc∆T ) to climate change.
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.
You are likely aware that diamonds are converted - albeit slowly - to graphite under normal conditions. Thus, diamonds don't last forever, in contrast to the popular advertising slogan. However, did you know that you can use chemistry to prove that diamonds are not forever? It's simpler than you think...
The solution to Chemical Mystery #11, which involves the Leidenfrost Effect, is presented.