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Thermodynamics and Statistical Mechanics (Basic Concepts In Chemistry)
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Thermodynamics
Statistical
undergraduate
statistical
thermodynamics.
Thermodynamic
quantities
relationships
introduced
thermodynamic
confidence.
development
illustrated
understand
transformations,
addressing
performed,
reactions,
temperature?How
endothermic
spontaneously,
spontaneously?What
determines
equilibrium
phases?How
temperature
equilibrium?What
entropy?How
macroscopic
thermodynamic
properties
microscopic
developing
thermodynamic
quantities
--Pharmaceutical
developing
thermodynamic
quantities
--Pharmaceutical
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七日畅销榜
新书热卖榜From Wikipedia, the free encyclopedia
For other forms of reversibility, see .
In , a reversible process -- or reversible cycle if the process is cyclic -- is a process that can be "reversed" by means of
changes in some property of the system without
of energy). Due to these infinitesimal changes, the system is in
throughout the entire process. Since it would take an infinite amount of time for the reversible process to finish, perfectly reversible processes are impossible. However, if the system undergoing the changes responds much faster than the applied change, the deviation from reversibility may be negligible. In a reversible cycle, the system and its surroundings will be exactly the same after each cycle.
In thermodynamics, processes can be carried out in one of two ways: reversibly or irreversibly. Reversibility in thermodynamics refers to performing a reaction continuously at equilibrium. In an ideal thermodynamically reversible process, the energy from work performed by or on the system would be maximized, and that from hea heat cannot fully be converted to work and will always be lost to some degree (to the surroundings). The phenomenon of maximized work and minimized heat can be visualized on a pressure-volume curve, as the area beneath the equilibrium curve, representing work done. In order to maximize work, one must follow the equilibrium curve closely. Irreversible processes, on the other hand, are a result of straying away from the curve, therefore decreasing the amount
an irreversible process can be described as a thermodynamic process that leaves equilibrium. When described in terms of pressure and volume, it occurs when the pressure or the volume of a system changes so dramatically and instantaneously that the other (pressure or volume in this case) does not have time to catch up. A classic example of irreversibility is allowing a certain volume of gas to be released into a vacuum. By releasing pressure on a sample and thus allowing it to occupy a large space, the system and surroundings will have completely left equilibrium, and heat dissipation will be large compared to the little work done.
An alternative definition of a reversible process is a process that, after it has taken place, can be reversed and causes no change in either the
or its surroundings. In thermodynamic terms, a process "taking place" would refer to its transition from its initial
to its final state.
In an , fin therefore the system is not at equilibrium throughout the process. At the same point in an irreversible cycle, the system will be in the same state, but the surroundings are permanently changed after each cycle.
Reversible
process: The state on the left can be reached from the state on the right as well as vice versa without exchanging heat with the environment.
A reversible process changes the state of a system in such a way that the net change in the combined
of the system and its surroundings is zero. Reversible processes define the boundaries of how
can be in thermodynamics and engineering: a reversible process is one where no heat is lost from the system as "waste", and the machine is thus as efficient as it can possibly be (see ).
In some cases, it is important to distinguish between reversible and . Reversible processes are always quasistatic, but the converse is not always true. For example, an infinitesimal compression of a gas in a cylinder where there exists
between the piston and the cylinder is a quasistatic, but not reversible process. Although the system has been driven from its equilibrium state by only an infinitesimal amount, heat has been irreversibly lost due to , and cannot be recovered by simply moving the piston infinitesimally in the opposite direction.
, the term Tesla principle was used to describe (amongst other things) certain reversible processes invented by . However, this phrase is no longer in conventional use. The principle was that some systems could be reversed and operated in a complementary manner. It was developed during Tesla's research in
where the current's magnitude and direction varied cyclically. During a demonstration of the , the disks revolved and machinery fastened to the shaft was operated by the engine. If the turbine's operation was reversed, the disks acted as a .
Sears, F.W. and Salinger, G.L. (1986), Thermodynamics, Kinetic Theory, and Statistical Thermodynamics, 3rd edition (Addison-Wesley.)
Zumdahl, Steven S. (2005) "10.2 The Isothermal Expansion and Compression of an Ideal Gas." Chemical Principles. 5th Edition. (Houghton Mifflin Company)
Lower, S. (2003) Entropy Rules! What is Entropy?
Giancoli, D.C. (2000), Physics for Scientists and Engineers (with Modern Physics), 3rd edition (Prentice-Hall.)
, January 1919. p. 615.
"Tesla's New Monarch of Machines". New York Herald Tribune, Oct. 15, 1911. (Available online. Tesla Engine Builders Association. )