These bubble tubes are beautifully engineered pieces of science equipment for physics labs. You can get a set where each tube is filled with a liquid of different viscosity. Try filling them with your own liquids and have your students guess the liquid by the speed at which a bubble moves down the tube when it is angled at an incline.
Do you have any recommended science experiments using inexpensive materials? Did you find these ones useful? Let us know what you think.