The general state of the substance in the chemistry refers to the physical state obtained under the air pressure 1 bar (100 kPa). The air pressure here is recently modified to 1 standard atmospheric pressure by IUPAC. The material standard state can be defined at any given temperature. When a chemical reaction uses a standard state, it indicates that all solution molar concentrations were 1 mol / L or 1 mol / kg. Pure liquid and solid are in standard state.
For a given substance, the standard state is a reference state in which the thermodynamic state is such as an enthalpy, entropy, Gibbs free energy and other standards. The standard molar generating enthalpy of the element is equal to 0.