code: def Hvap(self):
          r'''Enthalpy of vaporization of the chemical at its current temperature,
          in units of [J/kg].
  
          This property uses the object-oriented interface
          :obj:`thermo.phase_change.EnthalpyVaporization`, but converts its
          results from molar to mass units.
  
          Examples
          --------
          >>> Chemical('water', T=320).Hvap
          2389540.219347256
          '''
          Hvamp = self.Hvapm
          if Hvamp:
              return property_molar_to_mass(Hvamp, self.MW)
          return Nonf Hvap(self):
          r'''Enthalpy of vaporization of the chemical at its current temperature,
          in units of [J/kg].
  
          This property uses the object-oriented interface
          :obj:`thermo.phase_change.EnthalpyVaporization`, but converts its
          results from molar to mass units.
  
          Examples
          --------
          >>> Chemical('water', T=320).Hvap
          2389540.219347256
          '''
          Hvamp = self.Hvapm
          if Hvamp:
              return property_molar_to_mass(Hvamp, self.MW)
          return None
docs: r'''Enthalpy of vaporization of the chemical at its current temperature,
          in units of [J/kg].
  
          This property uses the object-oriented interface
          :obj:`thermo.phase_change.EnthalpyVaporization`, but converts its
          results from molar to mass units.
  
          Examples
          --------
          >>> Chemical('water', T=320).Hvap
          2389540.219347256