Question

Does all object having same volume and same dencity why

Answer 1

Density is a characteristic property of a substance. Density equals the mass of the substance divided by its volume; D = m/v. Objects with the same volume but different mass have different densities.

Unlike the mass and volume that may be different for each specimen, all objects made of the same material will have the same density. Because of this the density is often used to identify unknown substances or to determine the percent composition.