State and Properties

The state of a system is determined by its properties such as volume, pressure, and temperature. The properties of a substance describe its present state and do not give a record of its previous history. The difference in any property between the two states depends solely upon those states themselves, and not upon the manner in which the system may pass from one state to the other.

  • Point property: The change in property values depend only on the initial and final states of them.
    e.g.: internal energy, enthalpy, entropy.

  • Path property: The change in property values depend also on the path by which the process is carried-out, in addition to the initial and final states of the system.
    e.g.: work, heat.

  • Extensive properties: These depend on the quantity (or extent) of matter contained in the system. Mass and volume are extensive properties. The total value of any extensive property is the sum of the values of the property of individual portions into which the system can be subdivided.

  • Intensive properties: Independent of the size of the system. Pressure, temperature, specific volume, density, etc., are intensive properties. Some intensive properties are derived from the extensive properties by specifying the unit amount of the substance concerned.
    e.g.: specific volume, specific heat, density.



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