text: An enthalpy–entropy chart, also known as the  H–S chart or Mollier diagram, plots the total heat against entropy, describing the enthalpy of a thermodynamic system. A typical chart covers a pressure range of 0.01–1000 bar, and temperatures up to 800 degrees Celsius. It shows enthalpy  in terms of internal energy , pressure  and volume  using the relationship  (or, in terms of specific enthalpy, specific entropy and specific volume,  ).