Before revision: Ideal gas law Classical ideal gas law The classical ideal gas law may be written In the form shown above, the equation of state is thus If the calorically perfect gas approximation is used, then the ideal gas law may also be expressed as follows where is the density, is the (constant) adiabatic index (ratio of specific heats), is the internal energy per unit mass (the "specific internal energy"), is the constant specific heat at constant volume, and is the constant specific heat at constant pressure.
After revision: Ideal gas law Classical ideal gas law The classical ideal gas law may be written In the form shown above, the equation of state is thus If the calorically perfect gas approximation is used, then the ideal gas law may also be expressed as follows where is the density, is the (constant) adiabatic index (ratio of specific heats), is the internal energy per unit mass (the "specific internal energy"), is the specific heat capacity at constant volume, and is the specific heat capacity at constant pressure.