The normal density rod (AP4632) sinks in warm water and floats in cold water. The reverse density rod works just the opposite! It will float in water 30-35 ºC and sink in cool water! Using both rods will enhance your ability to make density meaningful to your students. The reverse density rod will force students to think about the concept of density in a very fundamental way. This demonstration will also dramatically call attention to the fact that the properties and makeup of the rod as well as the properties of the liquid must always be considered.