Students were asked to estimate the mass of the air, and then were challenged to actually try to measure it. Students were asked what information was needed? Volume? Density? This activity leads into a decent discussion on significant figures and measurement. Students were told that we would not be calculating significant figures in physics, and this activity demonstrated why 340.4522 kg wasn’t any more accurate (or higher resolution) than 340. kg.
For those wondering about using sig figs in physics… We don’t use them in the “real world” so why use it in a high school classroom? If I really want to talk about accuracy and repeatability, I’ll use specific +/- tolerances.