The Devil's Milkshake is a simple, yet interesting chemistry experiment that fits well as a Halloween demo.
I think this experiment provides a fantastic vehicle to involve students of all ages in small, hands-on and exploratory research projects. Like many others, my students and I have investigated various aspects of this interesting fountain.
This is a series of experiments, PhET Interactive Simulation activities, and clicker questions to relate macroscopic and molecular representations of homogenenous solutions. Graphing skills are also used.
I came across a simple, yet interesting experiment that was first described by Elizabeth Sumner Walter in 2001. She merely had students pour water into a dish containing some Gobstoppers candies.