Mass is a measure of how much matter an object contains. If one object is more massive than another then this simply means that it contains more matter. Mass is measured in units called kilograms (kg)
Volume is a measure of space (e.g. how much space a physical object takes up, or how much empty space is available etc). Volume is measured in cubic meters (m3)
Density is simply a measure of how much mass is ""packed"" into a given volume. Density is measured in kilograms per cubic metre Kgm-3.
Density = Mass/Volume
So to calculate density we must first measure the mass of an object and calculate its volume. To determine the volume of regular shaped objects e.g cubes and spheres we can use basic mathematical equations, however this cannot be done for irregular shaped objects. One technique that can be used is to immerse irregular shaped objects in a fluid contained in a regular shaped container (e.g. a cylindrical measuring vessel). We then calculate the volume of the liquid that is displaced when the object is fully immersed. This is equal to the volume of the immersed object.