Many students have owned or seen fluids toys in which two immiscible fluids within a closed container can be tilted to generate waves. These types of inexpensive and readily available toys are fun to play with, but they are also useful for provoking student learning about fluid properties or complex fluid behavior, including drop formation and coalescence. Including these toys in a class or lab with a companion exercise allows students to use observation and inductive reasoning to infer principles-all while having fun.
Saviz, C. M.,
Serious Fun: Using toys to demonstrate fluid mechanics principles.
Physics Teacher, 52(6), 332–335.