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Heat capacity or thermal capacity is a measurable physical quantity equal to the ratio of the heat added to (or removed from) an object to the resulting temperature change. The SI unit of heat capacity is joule per kelvin and the dimensional form is . Specific heat is the amount of heat needed to raise the temperature of a certain mass by 1 degree Celsius. Heat capacity is an extensive property of matter, meaning it is proportional to the size of the system. When expressing the same phenomenon as an intensive property, the heat capacity is divided by the amount of substance, mass, or volume, so that the quantity is independent of the size or extent of the sample. The molar heat capacity is the heat capacity per unit amount (SI unit: mole) of a pure substance and the specific heat capacity, often simply called specific heat, is the heat capacity per unit mass of a material. Occasionally, in engineering contexts, the volumetric heat capacity is used. Temperature reflects the average randomized kinetic energy of constituent particles of matter (e.g. atoms or molecules) relative to the centre of mass of the system, while heat is the transfer of energy across a system boundary into the body other than by work or matter transfer. Translation, rotation, and vibration of atoms represent the degrees of freedom of motion which classically contribute to the heat capacity of gases, while only vibrations are needed to describe the heat capacities of most solids , as shown by the Dulong–Petit law. Other, more exotic contributions can come from magnetic and electronic degrees of freedom in solids, but these rarely make substantial contributions. For quantum mechanical reasons, at any given temperature, some of these degrees of freedom may be unavailable, or only partially available, to store thermal energy. In such cases, the specific heat capacity is a fraction of the maximum. As the temperature approaches absolute zero, the specific heat capacity of a system approaches zero, due to loss of available degrees of freedom. Quantum theory can be used to quantitatively predict the specific heat capacity of simple systems. == History == (詳細はearly modern period, heat was thought to be a measurement of an invisible fluid, known as the ''caloric''. Bodies were capable of holding a certain amount of this fluid, hence the term ''heat capacity'', named and first investigated by Scottish chemist Joseph Black in the 1750s. Since the development of thermodynamics during the 18th and 19th centuries, scientists have abandoned the idea of a physical caloric, and instead understand heat as changes in a system's internal energy. That is, heat is no longer considered a fluid; rather, heat is a transfer of disordered energy. Nevertheless, at least in English, the term "heat capacity" survives. In some other languages, the term ''thermal capacity'' is preferred, and it is also sometimes used in English. 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「Heat capacity」の詳細全文を読む スポンサード リンク
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