This lab activity allows students to demonstrate their knowledge of density by creating a cardboard cube of a known density. Each lab group has a different density cube to create, thus forcing each group to think for themselves.
Most students struggled with trying to figure out how big the cube should be. Many of them chose the maximum mass (500 grams) and then calculated the volume, which turns out to be enormous, depending on the density. Instead, the most successful groups chose a mass (say, 50 grams) and then calculated the size of cube they'd need to build to hold that mass. This does result in them packing the cube entirely full of bb's, which, if they didn't measure very well, becomes a challenge for them.
I made two example cubes (0.6 g/cm3 and 2.4 g/cm3) to show the students examples. They are typically surprised to see that the 2.4 g/cm3 is the smaller of the two cubes. I made the 2.4 g/cm3 cube by create a 1cm x 1cm x 1cm cube and then filling it with copper bb's.
For the lab, I put out scissors, cardboard, tape, and the copper bb's. You can choose just about any item to fill the cubes with, as long as the filler has a density greater than the largest density that any particular group has.
I checked in each group's results by measuring the LxWxH and the mass, then calculating the density. If they were not within 0.1 g/cm3, I typically had them go back and redo or recalculate.