AskDefine | Define calories

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Noun

calories
  1. Plural of calorie

Extensive Definition

This article is about the unit of energy. For its use in nutrition and food labelling regulations, see the article on food energy.
The calorie is a pre-SI unit of energy, in particular heat. In most fields, its use is archaic, and the SI unit of energy, the joule, has become accepted. However, it remains in common use as a unit of food energy. It was first defined by Professor Nicolas Clément in 1824 as a kilogram-calorie, and this definition entered French and English dictionaries between 1841 and 1867. Etymology: French calorie, from Latin calor (heat).
The unit calorie has historically been used in two major alternate definitions that differ by a factor of 1000:
  • The small calorie, gram calorie, or calorie (symbol: cal) is the amount of heat (energy) required to raise the temperature of one gram of water by 1 °C.
  • The large calorie, kilogram calorie, kilocalorie (symbol: kcal), or Calorie (capital C) is the amount of heat (energy) needed to increase the temperature of one kg of water by 1 °C, exactly 1000 small calories, or about 4.184 kJ.
The second form is the one commonly used to express food energy. Its most common name is calorie; kilocalorie is sometimes used, more often in the symbol "kcal" than in the spelled out word.
Apart from these two major alternate definitions, there exist also minor variants of the definition of this unit, which differ in the exact experimental conditions used, most notably the start temperature of the water (see section below).
The factors used to convert measurements in calories to their equivalents in joules are numerically equivalent to expressions of the specific heat capacity of water in SI units. See "Versions" below for an explanation of the units.
1 calIT = 4.1868 J (1 J = 0.23885 calIT) (International Steam Table calorie, 1956)
1 calth = 4.184 J (1 J = 0.23901 calth) (Thermochemical calorie)
1 cal15 = 4.18580 J (1 J = 0.23890 cal15) (15°C calorie)

Versions

The energy needed to increase the temperature of a gram of water by 1 degree Celsius depends on the starting temperature and is difficult to measure precisely. Accordingly, there have been several definitions of the calorie:
The two perhaps most popular definitions used in older literature are the "15 °C calorie" and the "thermochemical calorie". Since the many different definitions are a source of confusion and error, all calories are now deprecated in favour of the SI unit for heat and energy: the joule (J).

References

calories in Arabic: سعرة حرارية
calories in Bosnian: Kalorija
calories in Bulgarian: Калория
calories in Catalan: Caloria
calories in Czech: Kalorie
calories in Danish: Kalorie
calories in German: Kalorie
calories in Estonian: Kalor
calories in Modern Greek (1453-): Θερμίδα
calories in Spanish: Caloría
calories in Esperanto: Kalorio
calories in Persian: کالری
calories in French: Calorie (unité)
calories in Galician: Caloría
calories in Korean: 칼로리
calories in Croatian: Kalorija
calories in Indonesian: Kalori
calories in Italian: Caloria
calories in Hebrew: קלוריה
calories in Luxembourgish: Kalorie
calories in Lithuanian: Kalorija
calories in Malay (macrolanguage): Kalori
calories in Dutch: Calorie
calories in Japanese: カロリー
calories in Norwegian: Kalori
calories in Polish: Kaloria
calories in Portuguese: Caloria
calories in Romanian: Calorie
calories in Russian: Калория
calories in Slovenian: Kalorija
calories in Serbian: Калорија
calories in Sundanese: Kalori
calories in Finnish: Kalori
calories in Swedish: Kalori
calories in Thai: แคลอรี
calories in Vietnamese: Ca-lo
calories in Turkish: Kalori
calories in Ukrainian: Калорія
calories in Yiddish: קאלערי
calories in Chinese: 卡路里
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