Ideal Gas Density
Ideal Gas Density
The density of a gas falls as it warms or its pressure drops — the reason hot air rises and balloons float.
From the ideal gas law ρ = p·M/(R·T). where p is the pressure, M the molar mass, R the gas constant and T the absolute temperature.
Inputs
p := 101325 Pa=101325 Pa
M := 0.029 kg/mol=0.03 kg/mol
R := 8.314 J/(mol·K)=8.31 kg·m^2/K/mol/s^2
T := 288 K=288 K
Apply the ideal gas law solved for density.
rho := p·M/(R·T)=1.23 kg/m^3
Results
Air at sea level and 15 °C comes out near 1.2 kg/m³. Heating the gas lowers its density, producing the buoyancy that lifts balloons and drives natural convection.
Assumptions & limitations
- Ideal-gas behaviour.
- Absolute temperature and pressure.
- Single-component gas.