A large object can have small mass if it has low density. For example, take an inflated balloon and a one troy ounce gold bar. The balloon has a higher volume but less mass than the gold bar.
This is because the density of the air in a balloon is very low; whereas, the density of the gold bar is much higher but has a lower volume.
Taking into account mass is found using mass = density/volume. The higher the density and the lower the volume the higher the mass is.
