Lesson Summary Students observe objects placed in water. Some sink and some float. They come up with an operational definition of density: objects float in water if they are less dense than water; objects sink if they are denser. Students then observe what happens when they first lower a small vial of hot water and later a vial of cold water into cups of room temperature water. They observe the less-dense warm water rise and the denser cold water sink. Teacher Background Hot and cold water interact with each other. Cold water descends to the bottom of a container because it is more dense and in the process it pushes the warmer water upward. The opening activity (Whole Class Demo) is not meant to give students a full understanding of density. Density is a concept that is difficult for this age-level to fully understand. For this investigation, students just need to understand that:  If an object floats in water, it is less dense than water; if an object sinks in water, the object is denser than water. Set-up/Management Tips Prepare the hot and cold water before hand. Red = Hot; Blue= Cold Fill two pitchers from a faucet and let them stand for an hour for the room temperature water. Be sure to have students practice lowering the stick and vial tool into the cup of clear room temperature water and fastening it in place with the clothes pin. Literacy Support Books Available Through VAST Mediagraphies: (see Literacy Links) Water in the Oceans – illustrates a “real Life” connection with Ocean current information. Science Stories “The Pond” Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: sink denser                        float                        less dense