Demo Idea: Density Spheres

Title: Steel Density Spheres
Source: http://www.teachersource.com/Density/DensityKits/SteelSphereDensityKit.aspx
Target Age: Grade 3+
Materials Required: Sphere Kit, Large glass bowl, Water
Prep Time Required: <5 minutes
Demo Time Required: <10 minutes
Description: The two spheres have approximately the same mass and appearance, but different densities and sizes. The smaller sphere sinks, but the larger floats. Before dropping the two in water, ask the class audience what they think will happen. Most likely is that the class will think that either they both sink, or only the large will sink. After you drop the balls into the water, ask the class what they think happened. Let them guess and experiment themselves by feeling the balls or dropping them in the water themselves. This experiment will help teach kids both the principle of density, and also that they should never take anything at face value, and should instead experiment to find out what's really true.