explain the concept of density of objects relative density or specific gravity of water and how an object will behave if placed in water?

Density:

It is define as mass per unit volume.

Units:

SI unit of density is Kg/m3.

Other units are given below,

g/cm3, g/mL, kg/L

Formula:

D=m/v

D = density

m=mass

V=volume

Symbol:

The symbol used for density is called rho. It is represented by ρ. However letter D can also be used to represent the density.

Specific gravity or relative density:

It is the ratio between the density of object and density of reference substance.

Mostly the water is taken as reference and its density is 1 g/cm³.

The value of specific density tell us weather the given substance will sink or float on reference substance.

For example:

Take the two equal amount of blocks one is made up of styrofoam and one is made up metal. Put these two blocks in to water. The block made up of metal will sink while the other made up of styrofoam will float on the surface of water because of difference in densities. The styrofoam is less denser than water while metal more denser then water.