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Physical properties of materials and systems are often described as intensive and extensive properties. This classification relates to the dependency of the properties upon the size or extent of the system or object in question. The distinction is based on the concept that smaller, non-interacting identical subdivisions of the system may be identified so that the property of interest does or does not change when the system is divided or combined. An intensive property is a bulk property, meaning that it is a physical property of a system that does not depend on the system size or the amount of material in the system. Examples of intensive properties include temperature, refractive index, density, and hardness of an object. When a diamond is cut, the pieces maintain their intrinsic hardness (until their size reaches a few atoms thick). By contrast, an extensive property is additive for independent, non-interacting subsystems.〔(IUPAC Green Book ) Quantities, Units and Symbols in Physical Chemistry (3rd edn. 2007), page 6 (page 20 of 250 in PDF file)〕 The property is proportional to the amount of material in the system. For example, both the mass and the volume of a diamond are directly proportional to the amount that is left after cutting it from the raw mineral. Mass and volume are extensive properties, but hardness is intensive. The ratio of two extensive properties of the same object or system is scale-invariant, and is therefore an intensive property. For example, the ratio of the extensive properties mass and volume, the density, is an intensive property. This terminology of intensive and extensive properties was introduced by Richard C. Tolman in 1917.〔 ==Intensive properties== An intensive property is a physical quantity whose value does not depend on the amount of the substance for which it is measured. For example, the temperature of a system in thermal equilibrium is the same as the temperature of any part of it. If the system is divided the temperature of each subsystem is identical. The same applies to the density of a homogeneous system; if the system is divided in half, the mass and the volume change in the identical ratio and the density remains unchanged. Additionally, the boiling point of a substance is another example of an intensive property. For example, the boiling point for water is 100 °C at a pressure of one atmosphere, which remains true regardless of quantity. According to the state postulate, a sufficiently simple thermodynamic system requires only two independent intensive variables to fully specify the system's entire state. Other intensive properties are derived from the two known values. Some intensive properties, such as viscosity, are empirical macroscopic quantities and are not relevant to extremely small systems. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Intensive and extensive properties」の詳細全文を読む スポンサード リンク
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