Density

density of liquid
1. water　　1 g / cm^3
2. mercury　13.59 g / cm^3
3. ethanol　0.79 g / cm^3
4. benzene　0.88 g / cm^3
5. CCl4　　1.59 g / cm^3
In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of cork or foam.
For the common case of a homogeneous substance, density is expressed as:
density = mass / volume
where, in SI Units:
ρ (rho) is the density of the substance, measured in kg m–3
m is the mass of the substance, measured in kg
V is the volume of the substance, measured in m3
I hope this can help your understanding. =)

水是liquid
水的density是１kg/liter
liquid的density是１kg/liter
少量水是少量liquid
少量水的density是１g/ml
少量liquid的density可以是１g/ml
大量水是大量liquid
大量水的density是１ton/m^3
大量liquid的density可以是１ton/m^3
density就是density，永遠都是density