Gas density is a physical property that indicates the mass of a gas per unit volume. Basically, it expresses how much matter is contained in a unit volume of gas. The density of a gas is usually denoted by the symbol ρ (rho) and is measured in units of mass per unit volume, such as kilograms per cubic meter (kg/m³) in the SI system of units.
The density of a gas depends on many factors such as the temperature, pressure and composition of the gas. At constant temperature and pressure, the density of a gas can be directly proportional to its molar mass. This means that gases with a higher molar mass usually have a higher density.
Gas density is an important physical property with many applications. It plays a key role in gas volume and mass calculations, gas physical and chemical properties analysis, gas pressure and volume calculations under various conditions, as well as various processes involving gases such as gas compression, capture and storage.
Gas density is also important in engineering and design, for example in the design and operation of gas pipelines, gas storage tanks, gas turbines and the like. As with liquids, the density of a gas affects its behavior under various conditions and is a key variable in solving many gas-related physics and engineering problems.