Question

show that mass and volume need not be equal​

Answer 1

Through the law of conservation of mass

Answer 2

Even though an atom must be smaller than an atom , it might have more mass . The mass of atoms , their size and how they are arranged determine the density of a substance ,. Density equals the mass of the object divided by it's volume , D= m/v . Objects with the same mass but different volume have different densities.