page_title: Isobaric process
hierarchical_section_title: Isobaric process
context_page_description: An Isobaric process is a thermodynamic process in which the pressure stays constant: ΔP = 0. The heat transferred to the system does work, but also changes the internal energy of the system. Using this convention, by the first law of thermodynamics,
  where W is work, U is internal energy, and Q is heat. Pressure-volume work by the closed system is defined as:
  where Δ means change over the whole process, whereas d denotes a differential. Since pressure is constant, this means that
  .
  Applying the ideal gas law, this becomes
  assuming that the quantity of gas stays constant, e.g., there is no phase transition during a chemical reaction. According to the equipartition theorem, the change in internal energy is related to the temperature of the system by
  ,
  where cV, m is molar heat capacity at a constant volume.
  Substituting the last two equations into the first equation produces:
  where cP is molar heat capacity at a constant pressure.
context_section_description: An Isobaric process is a thermodynamic process in which the pressure stays constant: ΔP = 0. The heat transferred to the system does work, but also changes the internal energy of the system.  This article uses the physics sign convention for work, where positive work is work done by the system.  Using this convention, by the first law of thermodynamics,
  where W is work, U is internal energy, and Q is heat. Pressure-volume work by the closed system is defined as:
  where Δ means change over the whole process, whereas d denotes a differential. Since pressure is constant, this means that
  .
  Applying the ideal gas law, this becomes
  assuming that the quantity of gas stays constant, e.g., there is no phase transition during a chemical reaction. According to the equipartition theorem, the change in internal energy is related to the temperature of the system by
  ,
  where cV, m is molar heat capacity at a constant volume.
  Substituting the last two equations into the first equation produces:
  where cP is molar heat capacity at a constant pressure.
caption: The yellow area represents the work done