masspervolume

Mass per volume is a measure of how much mass is contained in a given volume of a substance. It is commonly expressed as m/V, with common units including kilograms per cubic meter (kg/m^3) and grams per milliliter (g/mL). In homogeneous substances, mass per volume is the same as density, which is defined as mass per unit volume at a specified temperature and pressure. For porous or composite materials, a distinction is made between true density (mass per particle volume) and bulk density (mass per total, accessible volume), which can differ from the simple mass/volume ratio.

Measurement can be straightforward for simple solids or liquids: determine the mass of a sample and the volume it occupies, then compute m/V. For irregular shapes, volume can be found by water displacement or by using a pycnometer for precise density determinations. In gases, density depends on temperature and pressure and can be estimated using the ideal gas law, ρ = pM/(RT), where M is the molar mass.

Applications of mass per volume span many fields. In chemistry and medicine, it relates to concentrations such as mass concentration (solids per volume of solution) and dosing calculations. In materials science and geology, bulk density informs porosity and compaction. In environmental science, mass per volume helps quantify contaminant loads in air or water. The value of mass per volume is inherently condition-dependent for gases and is typically specified at standard or reference conditions for liquids and solids.