After a brief quiz on the states of matter today, we went back and looked over the physical and chemical change lab from last Friday. (lab link) Each group was assigned a station to present with their whiteboards. ( I borrowed a couple stations from the modeling chemistry version of the lab)
Corn Starch and Water
Students debated what happened in each station. Some said it was chemical change since there were new properties which may mean their was a new substance. In the end we agreed it was a physical change since you could still separate the two with physical means.
They had to pay attention to the masses. This group correctly recognized that the mass gained was from oxygen.</a
Sugar and Water, Alka Seltzer and Water
While I had done a similar station last year, I added in the massing this year. This station always leads to a interesting discussion of the permanence of matter when things ‘disappear’ as they dissolve.
Water as ice and liquid
Mass was also important here. But we broke several 10ml graduated cylinders when we froze water in them. They were really old cylinders, but still didn’t figure out if they broke from microfractures or just temperature shock.