Calorie 6423 225997112 2008-07-16T11:12:40Z Gwernol 266416 Reverted edits by [[Special:Contributions/Lozzy090|Lozzy090]] ([[User talk:Lozzy090|talk]]) to last version by Smitty :''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]].<ref name="iso31-4">International Standard [[ISO 31-4]]: Quantities and units&nbsp;– Part 4: Heat. Annex B (informative): Other units given for information, especially regarding the conversion factor. [[International Organization for Standardization]], 1992.</ref> 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&nbsp;[[degree Celsius|°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 [[kilogram|kg]] of water by 1&nbsp;°C, exactly 1000 small calories, or about 4.184 [[kilojoule|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 unit]]s. See "Versions" below for an explanation of the units. :1 cal<sub>IT</sub> <!--(international)--> = 4.1868 J (1 J = 0.23885 cal<sub>IT</sub>) (International Steam Table calorie, 1956) :1 cal<sub>th</sub> <!--(thermo)--> = 4.184 J (1 J = 0.23901 cal<sub>th</sub>) (Thermochemical calorie) :1 cal<sub>15</sub> <!-- (14.5–15.5 &nbsp;°C) --> = 4.18580 J (1 J = 0.23890 cal<sub>15</sub>) (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: * '''[[Thermochemistry|Thermochemical]] calorie''' (cal<sub>th</sub>): <font color="#285000">4.184</font>&nbsp;J exactly.<ref name="iso31-4" /> * '''15&nbsp;°C calorie''' (cal<sub>15</sub>): the amount of energy required to warm 1&nbsp;g of air-free water from 14.5&nbsp;°C to 15.5&nbsp;°C at a constant pressure of 101.325&nbsp;kPa (1 [[atmosphere (unit)|atm]]). Experimental values of this calorie ranged from 4.1852&nbsp;J to 4.1858&nbsp;J. The [[CIPM]] in 1950 published a mean experimental value of <font color="#285000">4.1855</font>&nbsp;J, noting an uncertainty of 0.0005&nbsp;J.<ref name="iso31-4" /> * '''20&nbsp;°C calorie''': the amount of energy required to warm 1&nbsp;g of air-free water from 19.5&nbsp;°C to 20.5&nbsp;°C at a constant pressure of 101.325&nbsp;kPa (1 [[atmosphere (unit)|atm]]). This is about <font color="#285000">4.182</font>&nbsp;J. * '''4&nbsp;°C calorie''': the amount of energy required to warm 1&nbsp;g of air-free water from 3.5&nbsp;°C to 4.5&nbsp;°C at a constant pressure of 101.325&nbsp;kPa (1 [[atmosphere (unit)|atm]]). * '''Mean calorie''': 1/100 of the amount of energy required to warm 1&nbsp;g of air-free water from 0&nbsp;°C to 100&nbsp;°C at a constant pressure of 101.325&nbsp;kPa (1 [[atmosphere (unit)|atm]]). This is about <font color="#285000">4.190</font>&nbsp;J * '''International Steam Table Calorie (1929)''': (1/860)&nbsp;[[watt|W]]&nbsp;h = (180/43)&nbsp;J exactly. This is approximately <font color="#285000">4.1868</font>&nbsp;J. * '''International Steam Table Calorie (1956)''' (cal<sub>IT</sub>): 1.163&nbsp;m[[watt|W]]&nbsp;h = <font color="#285000">4.1868</font>&nbsp;J exactly. This definition was adopted by the Fifth International Conference on Properties of Steam (London, July 1956).<ref name="iso31-4" /> * '''IUNS calorie''': <font color="#285000">4.182</font>&nbsp;J exactly. This is a ratio adopted by the Committee on Nomenclature of the International Union of Nutritional Sciences.<ref>{{cite web |url=http://www.fao.org/docrep/meeting/009/ae906e/ae906e17.htm |author=FAO |authorlink=FAO |title=The adoption of joules as units of energy |year=1971 |quote=While the nutritional calorie has not been defined, basically it is the thermochemical calorie. The standards used in calorimetric work in nutrition is ultimately the heat of combustion of an internationally graded standard benzoic acid. This is primarily expressed as joules per gramme mole and secondarily as thermochemical calories per mole derived by dividing by 4.182, a factor which has been approved by the Committee on Nomenclature of the IUNS.}}</ref> The two perhaps most popular definitions used in older literature are the "15&nbsp;°C calorie" and the "thermochemical calorie". Since the many different definitions are a source of confusion and error, all calories are now [[deprecation|deprecated]] in favour of the [[SI]] unit for heat and energy: the [[joule]] (J). ==References== {{reflist}} [[Category:Units of energy]] [[ar:سعرة حرارية]] [[be-x-old:Калёрыя]] [[bs:Kalorija]] [[bg:Калория]] [[ca:Caloria]] [[cs:Kalorie]] [[da:Kalorie]] [[de:Kalorie]] [[et:Kalor]] [[el:Θερμίδα]] [[es:Caloría]] [[eo:Kalorio]] [[fa:کالری]] [[fr:Calorie (unité)]] [[gl:Caloría]] [[ko:칼로리]] [[hr:Kalorija]] [[id:Kalori]] [[it:Caloria]] [[he:קלוריה]] [[lb:Kalorie]] [[lt:Kalorija]] [[ms:Kalori]] [[nl:Calorie]] [[ja:カロリー]] [[no:Kalori]] [[pl:Kaloria]] [[pt:Caloria]] [[ro:Calorie]] [[ru:Калория]] [[simple:Calorie]] [[sl:Kalorija]] [[sr:Калорија]] [[su:Kalori]] [[fi:Kalori]] [[sv:Kalori]] [[th:แคลอรี]] [[vi:Ca-lo]] [[tr:Kalori]] [[uk:Калорія]] [[yi:קאלערי]] [[zh:卡路里]]