The concept of density is investigated regularly- in lecture, lab, or both- in Introductory (non-science majors) or the majors General Chemistry 1 courses. This post describes a short activity involving ice core density.
Ever wonder why some call precipitation reactions "double decomposition". Perhaps (or perhaps not) two (double) salts are sort of splitting apart (decomposing?) and then reforming with other radicals. But a solvent (usually water) is necessary to achieve the desired effect. But is adding water to a salt really decomposition?
My first experiment involves measuring the density of water. Each group of two kids is assigned a specific volume of water from 10 to 100 mLs on the tens. They simply measure the mass of an empty graduated cylinder and then add the water and find the mass again. Once they have their data they go around the room and find another group that has one of the volumes that they need and get the data from them and record their names. Once complete they generate a graph of the data and answer a few simple questions. The whole procedure can be completed in about 20 minutes.
This activity is used as a reinforcement activity following my use of JCE Classroom Activity #113: An Interlocking Building Block Activity in Writing Formulas of Ionic Compounds. It could be used as a stand alone activity to support writing ionic formulas and names.