An important concept in chemistry is that the mass of an object will always be the sum of the masses of its parts. To illustrate this concept, mix 1/2 pound of salt with 1/2 pound of rice and 1/2 pound of sugar. The result is 1 1/2 pounds of matter. Pupils also learn that these component parts can be changed but never lose mass.
Fifth-graders typically learn that matter can change from one state to another, from solid to liquid to gas. Sixth-graders build on this by learning that one compound can exist in all these forms. To demonstrate the states of matter, experiment with the solid, liquid and gaseous forms of water. Show pupils how water changes from ice to liquid to vapor.
Pupils at this age learn that substances are made of combinations of other substances. Sixth-graders study how materials can be broken down into their component parts. Pupils learn how physical changes occur when materials are mixed and how substances can be separated using processes such as filtration and evaporation. One related activity is to study the evaporation of salt water; as the water evaporates, the salt remains.
Pupils can practice conducting experiments in these grades. For example, when baking soda is combined with vinegar, pupils will remember the fizzing reaction for a long time.