This lab will elicit a lot of "OHH's" and "AHH's" from your students. Very short, simple and inexpensive to implement. I use it to reinforce observation skills as well as how to measure liquid volume using graduated cylinders and beakers. Students are asked to explain the events that they observe in this activity. Add to that the fact that they get to use test tubes and you have a hit on your hands with middle school kids.