Fig. 1. Improper approach to measuring the mass of air.
Fig. 2. A vacuum container, a PET bottle, and a rubber balloon can be used to weigh air.
Fig. 3. Open view of the bicycle pumps used to fill the PET bottle (a) and to remove air from the vacuum container (b).
Fig. 4. Linear relationship between the mass of air and the number of strokes (bottom axis) and volume (top axis) in the PET bottle measurement. Error bars are associated to volume values.