A change of amount of electric polarization is associated with an electric field change. An entropy change is associated with a temperature change. For example, a volume transfer is associated with a change in pressure. In a thermodynamic system, transfers of extensive quantities are associated with changes in respective specific intensive quantities. Likewise, a change of amount of electric polarization in a system is not necessarily matched by a corresponding change in electric polarization in the surroundings. In a thermodynamic process in which a quantity of energy is transferred from the surroundings into or out of a system as heat, a corresponding quantity of entropy in the system respectively increases or decreases, but, in general, not in the same amount as in the surroundings. On the other hand, some extensive quantities measure amounts that are not conserved in a thermodynamic process of transfer between a system and its surroundings. Likewise, volume may be thought of as transferred in a process in which there is a move of the wall between two systems, increasing the volume of one and decreasing that of the other by equal amounts. For example, species of matter may be transferred through a semipermeable membrane. They are transferred across a wall between two thermodynamic systems, or subsystems. In thermodynamics, some extensive quantities measure amounts that are conserved in a thermodynamic process of transfer. The density of water is approximately 1g/mL whether you consider a drop of water or a swimming pool, but the mass is different in the two cases.ĭividing one extensive property by another extensive property generally gives an intensive value-for example: mass (extensive) divided by volume (extensive) gives density (intensive).Įxamples of extensive properties include: The related intensive quantity is the density which is independent of the amount. For example, the mass of a sample is an extensive quantity it depends on the amount of substance. See List of materials properties for a more exhaustive list specifically pertaining to materials.Īn extensive property is a physical quantity whose value is proportional to the size of the system it describes, or to the quantity of matter in the system. specific conductance (or electrical conductivity).Other intensive properties are derived from those two intensive variables.Įxamples of intensive properties include:
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For example, in thermodynamics, the state of a simple compressible system is completely specified by two independent, intensive properties, along with one extensive property, such as mass. The distinction between intensive and extensive properties has some theoretical uses. For example, the boiling point of water is 100 ☌ at a pressure of one atmosphere, which remains true regardless of quantity. Additionally, the boiling point of a substance is another example of an intensive property. Likewise for the density of a homogeneous system if the system is divided in half, the extensive properties, such as the mass and the volume, are each divided in half, and the intensive property, the density, remains the same in each subsystem. If the system is divided by a wall that is permeable to heat or to matter, the temperature of each subsystem is identical if a system divided by a wall that is impermeable to heat and to matter, then the subsystems can have different temperatures. For example, the temperature of a system in thermal equilibrium is the same as the temperature of any part of it. Īn intensive property is a physical quantity whose value does not depend on the amount of the substance for which it is measured. The terms intensive and extensive quantities were introduced into physics by German writer Georg Helm in 1898, and by American physicist and chemist Richard C.
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For example, the square root of the mass is neither intensive nor extensive. Though it is very often convenient to define physical quantities to make them intensive or extensive, they do not necessarily fall under those classifications. Examples of intensive properties include temperature, T refractive index, n density, ρ and hardness of an object, η.īy contrast, extensive properties such as the mass, volume and entropy of systems are additive for subsystems. It is not necessarily homogeneously distributed in space it can vary from place to place in a body of matter and radiation. Īn intensive property does not depend on the system size or the amount of material in the system.
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According to IUPAC, an intensive quantity is one whose magnitude is independent of the size of the system whereas an extensive quantity is one whose magnitude is additive for subsystems. Physical properties of materials and systems can often be categorized as being either intensive or extensive, according to how the property changes when the size (or extent) of the system changes.