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State postulate for incompressible substance

  1. Jan 10, 2016 #1
    State postulate for a simple compressible system is completely specified by two independent intensive properties.
    But what about state postulate for a incompressible system.
    Why it is not so important?
  2. jcsd
  3. Jan 10, 2016 #2
    Please identify what you consider an incompressible system.
  4. Jan 11, 2016 #3
    just considering only liquids specifically water
  5. Jan 11, 2016 #4
    Liquid water is compressible, so it still takes specification of two intensive properties to define its thermodynamic equilibrium state. See the phase diagram for water.
  6. Jan 12, 2016 #5
    Let it be, but, in most cases especially fluid mechanics we treat water as an incompressible liquid. Anyway if there is an incompressible substance, what are the basic properties which are required to completely specify its state. Why no textbooks did mention about the state postulate of incompressible substances?
  7. Jan 12, 2016 #6
    It's certainly mentioned in thermodynamics books. Look up Poynting Correction.

  8. Jan 12, 2016 #7
    I'm sure you are aware that there is no such thing as a completely incompressible liquid.
  9. Jan 12, 2016 #8
    Ok sir. Then what about the state postulate for solids
  10. Jan 12, 2016 #9
    How can we define the state of solids
  11. Jan 12, 2016 #10
    For homogeneous isotropic single phase solids, two intensive variables are still required. Incidentally, for solids, Hooke's law in 3D automatically has compressibility built into the relationship.

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