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A thermodynamic system is a quantity of matter described by a set of properties. In classical thermodynamics, these are simple quantities which are uniform throughout the sample. |
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The quantity of matter in a thermodynamics system is usually given in terms of either mass (a concept of mechanics), or moles (a concept of chemistry). Other properties may be considered as extensive (depending on the quantity of matter within the system), or intensive, independent of the quantity. Extensive properties are often given on per unit mass or per mole basis, which is an intensive property.
This is an extensive property involving involves geometric definitions and the physical boundaries of a state. The volume per unit of mass is the mathematical inverse of density in rigid body or nonrigid mechanics. The molar volume is the volume per mole.
This intensive property is the same quantity as considered in nonrigid mechanics. In classical thermodynamics, the pressure which a system exerts on its surroundings and the pressure of the surroundings on a system are considered to either in equilibrium so that the system is neither expanding nor contracting, or the difference is infinitesimal (arbitrarily small).
This corresponds roughly to the a sense of "hotness" or "coldness". It can be measured by changes in properties of a body (such as volume, pressure, radiation), and most particularly the properties of an ideal gas. This quantity does not correspond to any quantity of classical mechanics, but it can be defined on the basis of statistical mechanics.
This the quantity of a thermodynamic system that changes when a system is heated or cooled. It can be defined using statistical mechanics, and changes in it can be computed using quantities of work and heat. Changes in energy are subject to the first law of thermodynamics, the conservation of energy.
This quanty does not correspond to anything that can be directly observed. It is mathematically defined as reversible heat per unit of temperature. It correspond to randomness or disorder at a molecular level. Changes in entropy are the subject of the second law of thermodyanmics.
This is a computed quantity, and corresponds roughly to heat.
H (Enthalpy)= E + PV
A= E - TS
G = E + PV - TS
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Connections to other areas of science including applications to chemistry, astronomy, earth science, and biology can be developed. Other areas of physics including mechanics, other areas of thermodynamics, electromagnetism, relativity, quantum theory, and the structure of matter are significant. |
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