AskDefine | Define kilocalories

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

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