code: def Cpg(self):
          r'''Gas-phase heat capacity of the chemical at its current temperature,
          in units of [J/kg/K]. For calculation of this property at other
          temperatures, or specifying manually the method used to calculate it,
          and more - see the object oriented interface
          :obj:`thermo.heat_capacity.HeatCapacityGas`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> w = Chemical('water', T=520)
          >>> w.Cpg
          1967.6698314620658
          '''
          Cpgm = self.HeatCapacityGas(self.T)
          if Cpgm:
              return property_molar_to_mass(Cpgm, self.MW)
          return Nonf Cpg(self):
          r'''Gas-phase heat capacity of the chemical at its current temperature,
          in units of [J/kg/K]. For calculation of this property at other
          temperatures, or specifying manually the method used to calculate it,
          and more - see the object oriented interface
          :obj:`thermo.heat_capacity.HeatCapacityGas`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> w = Chemical('water', T=520)
          >>> w.Cpg
          1967.6698314620658
          '''
          Cpgm = self.HeatCapacityGas(self.T)
          if Cpgm:
              return property_molar_to_mass(Cpgm, self.MW)
          return None
docs: r'''Gas-phase heat capacity of the chemical at its current temperature,
          in units of [J/kg/K]. For calculation of this property at other
          temperatures, or specifying manually the method used to calculate it,
          and more - see the object oriented interface
          :obj:`thermo.heat_capacity.HeatCapacityGas`; each Chemical instance
          creates one to actually perform the calculations. Note that that
          interface provides output in molar units.
  
          Examples
          --------
          >>> w = Chemical('water', T=520)
          >>> w.Cpg
          1967.6698314620658