I taught my seventh grade class how to use the triple beam balances today. The activity was kind of stupid; I just had them list, predict, and then measure the mass of an assortment of objects, many of their own choosing. It's totally pointless, but kids like playing with the balances and this gives them a chance to just explore while practicing a skill, and possibly to begin to get a sense of what a gram feels like. It was actually a satisfying period with this rather difficult group of kids, I guess because it was easy, they'd used the balances a few times last year (to my pleasant surprise), and it was easy for me to check in with each student and make sure he or she had mastered the skill.
Tomorrow, on to density.