Exhibit: Bubble Race
Which is stickier, cooking oil or shower gel? You can find out by turning the tubes upside down and seeing how long an air bubble takes to rise through the various liquids. The speed at which the bubbles travel gives you a good measure of how gooey, or viscous a liquid is. The viscosity of a liquid is often important for the job it has to do. Engine oil has to stick to the metal surfaces to protect them, but must not be so viscous that you cannot start the engine.