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Properties of isolated, closed, and open thermodynamic systems in exchanging energy and matter. A thermodynamic system is a body of matter and/or radiation separate from its surroundings that can be studied using the laws of thermodynamics.
A closed system is a natural physical system that does not allow transfer of matter in or out of the system, although – in the contexts of physics, chemistry, engineering, etc. – the transfer of energy (e.g. as work or heat) is allowed.
Open systems have input and output flows, representing exchanges of matter, energy or information with its surroundings. An open system is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the ...
The concept of an isolated system can serve as a useful model approximating many real-world situations. It is an acceptable idealization used in constructing mathematical models of certain natural phenomena ; e.g., the planets in the Solar System , and the proton and electron in a hydrogen atom are often treated as isolated systems.
For the first law of thermodynamics, there is no trivial passage of physical conception from the closed system view to an open system view. [68] [69] For closed systems, the concepts of an adiabatic enclosure and of an adiabatic wall are fundamental. Matter and internal energy cannot permeate or penetrate such a wall. For an open system, there ...
One such potential is the Helmholtz free energy (A), for a closed system at constant volume and temperature (controlled by a heat bath): = Another potential, the Gibbs free energy (G), is minimized at thermodynamic equilibrium in a closed system at constant temperature and pressure, both controlled by the surroundings:
a mechanically isolated system which can exchange heat but not mechanical work or matter, such as an uninsulated bomb calorimeter; a closed system which can exchange energy but not matter, such as an uninsulated closed piston or balloon; an open system which it can exchange both matter and energy with the surroundings, such as a pot of boiling ...
A fundamental difference exists between chemistry as it is performed in most laboratories and chemistry as it occurs in life. Laboratory processes are mostly designed such that the (closed) system goes thermodynamically downhill; i.e. the product state is of lower Gibbs free energy, yielding stable molecules that can be isolated and stored.