Physical Chemistry Lesson of the Day – Isolated, Closed and Open Systems

A thermodynamic system can be one of three types:

  • An isolated system cannot transfer energy or matter with its surroundings.  Other than the universe itself, an isolated system does not exist in practice.  However, a very well insulated and bounded system with negligible loss of heat is roughly an isolated system, especially when considered within a very short amount of time.  In mathematical and physical modelling, a hydrogen atom’s proton, a hydrogen atom’s electron and a planet are often treated each as an isolated system.
  • A closed system can transfer energy (heat or work) but not matter with its surroundings.
    • A system that allows work but not heat to be transferred with its surroundings is an adiabatically isolated system.
    • A system that allows heat but not work to be transferred with its surroundings is a mechanically isolated system.
  • An open system can transfer both energy and matter with its surroundings.

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