That's the definition of the density of the substance.
Density is the ratio of the mass of a substance to the volume of the substance.
density
Mass of a substance to its volume
The percentages refer to the amount of a substance of interest that is contained in a compound or mixture of that and other substances. Percentage by mass = 100*mass of substance of interest/total mass. Percentage by volume = 100*volume of substance of interest/volume mass. And, incidentally, the word is definition, not diffinition.
That depends on the substance. Different substances have different densities (mass / volume).
Its density.
Density
Density is the ratio of the mass of a substance to the volume of the substance.
Its density.
"density"
Its density.
Its density.
Density is the ratio of mass and volume.
density
This is the density.
volume
Its density.