To teach density in alignment with modeling instruction, I would have had students find a material’s density by measuring various mass and volumes. The density labs generally have students identify the unknown substances by comparing calculated density to known values. While what I envision would have taken longer, it would have allowed students to truly have a more innate understanding of Density. Today, we lectured that density is the amount of mass per unit volume of a substance.
Today, students calculated the densities of the items from the previous lab that was essentially practicing how to measure mass and volume. They measured the mass and volume for two cubes of uknown materials, two rods/cylinders of unknown metals, rock, and crayon. For the density lab, they calculated for the blocks and rods. Most of the students were not able to get the density for their rods to be close enough or similar to the substance’s known density. I was hoping that the value would at least be pretty close together. Some groups were successful in getting a number similar to each other. Some groups had VASTLY differing values. I revealed that the densities for the rods should have been similar. They were surprised.
I was convinced by the learning team that we could have the students design a lab AND cover CER for the rest of our class time. We did NOT have enough time. Last year, the students were able to do it all. We think it might have been because it was a Friday…Giving students something to play with (blown up balloons) after spending a while sitting might have been too much for a Friday. I think the way I would change this would be to include the density calculation in the Mass Communication Lab. THEN we would work on the CER and ask them what material they think their unknown substance is. It was pretty fun watching them measure the mass and volume of floating balloons.
Learning with Ms. Medrano 