Densitas

Densitas is a property that describes how much matter is contained in a given volume of a substance. In physics and common usage, it is usually called density. The standard definition is rho = m / V, where m is mass and V is volume. The SI unit is kilogram per cubic meter (kg/m^3); in many practical contexts, especially for solids and liquids, grams per cubic centimeter (g/cm^3) are used, with 1 g/cm^3 equal to 1000 kg/m^3.

Mass density refers to the amount of mass per unit volume. Relative density, or specific gravity, compares a material’s density to a reference density, typically that of water at a specified temperature. In geology and materials science, other forms such as bulk density (mass per total volume including pores) and true density (mass per solid volume) are used.

In statistics and probability theory, a density (probability density function) describes how probability is distributed over a continuous variable; the integral of the density over a region equals the probability of the variable falling in that region.

Densities are temperature and pressure dependent. Determining density can use methods such as Archimedes’ principle (buoyant force), hydrostatic weighing, pycnometry, gas pycnometry, or X-ray or gamma-ray densitometry.

Common examples: water has a density of about 1.0 g/cm^3 at 4 °C; air at sea level is about 0.001225 g/cm^3; metals often exceed several g/cm^3. Knowledge of density is important in material selection, buoyancy, fluid dynamics, and quality control.