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Properties of isolated, closed, and open systems in exchanging energy and matter. In thermodynamics, a closed system can exchange energy (as heat or work) but not matter, with its surroundings. An isolated system cannot exchange any heat, work, or matter with the surroundings, while an open system can exchange energy and matter.
Overall, in an isolated system, the internal energy is constant and the entropy can never decrease. A closed system's entropy can decrease e.g. when heat is extracted from the system. Isolated systems are not equivalent to closed systems. Closed systems cannot exchange matter with the surroundings, but can exchange energy.
In 1907, George H. Bryan wrote about systems between which there is no transfer of matter (closed systems): "Definition. When energy flows from one system or part of a system to another otherwise than by the performance of mechanical work, the energy so transferred is called heat."
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:
In thermodynamics, a closed system is one that cannot take in or give out ponderable matter, but may be able to take in or give out radiation and heat and work or any form of energy. In thermodynamics, a closed system can be further restricted, by being 'isolated': an isolated system cannot take in nor give out either ponderable matter or any ...
An isolated system has a fixed total energy and mass. A closed system, on the other hand, is a system which is connected to another, and cannot exchange matter (i.e. particles), but can transfer other forms of energy (e.g. heat), to or from the other system.
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The Gibbs free energy change ( = , measured in joules in SI) is the maximum amount of non-volume expansion work that can be extracted from a closed system (one that can exchange heat and work with its surroundings, but not matter) at fixed temperature and pressure.