Density is the Mass per unit Volume. Density often has units of grams per cubic centimeter (g/cm3). Remember, grams is a mass and cubic centimeters is a volume (the same volume as 1 milliliter). Major objective of this lecture is to present on Density. It is a tutorial based lecture. Density is not something that is directly measured. Typically if you want to know the density of something you will weigh it and then measure its volume. It is used quite often in identifying rocks and minerals since the density of substances rarely changes significantly.