Step-by-step explanation:
Density is defined as the amount of mass of a substance present in per unit volume.
Mathematically, Density =

As density is directly proportional to mass. So, a substance that has more mass will have more density.
Since, both soap and sponge are occupying same volume. But a soap bar is heavier than a piece of sponge because a soap bar has more mass than a sponge.
Thus, we can conclude that the soap is much more dense than the sponge because soap bar weighs more than a sponge.