In our previous papers, we reported a series of inferences based on a new thermodynamic theory: the state equation of real gas , gas solubility and gas-liquid interfacial tension , the specific heat capacity of real gas , the equilibrium distance of molecular interaction , and the state equation at isotherm . The new thermodynamics is founded on the revised thermodynamic laws: defining the heat with the first law and system work with the second law. It was verified to qualify as a basic principle of thermodynamics. Therefore, this paper will address molecular symmetry and entropy connected with the third law.