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Ideal gases do not possess potential energy

  1. Apr 20, 2014 #1
    Is it that ideal gases do not possess potential energy because there are no intermolecular forces. But, real gases do have potential energy and its potential energy is the highest among the different phases. ( Potential Energy of Gas>Liquid>Solid ). I need someone to make these things clear to me because I'm confused. Thank you.
  2. jcsd
  3. Apr 20, 2014 #2

    Andrew Mason

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    The molecules of the gas are point particles that do not interact with each other. So it does not take energy for the molecules of an ideal gas to separate from each other. This means that the internal energy consists only of kinetic energy (no potential energy).

    Real gases may consist of molecules that have attractive forces. A good example is water vapour. The polar nature of the the water molecules means that water molecules to be attracted to each other. It takes energy just to separate them (from ice → liquid or liquid → gas) without increasing their translational kinetic energies. This means that internal energy consists of both kinetic energy and the energy due to separation (potential energy).

    Since the molecules in water vapour have a greater separation than in liquid, vapour has more potential energy than liquid.

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