Most people associate calories with what we eat or drink, such as "This soda contains 200 calories". In fact, the calories listed on food packaging are calories, and the capital letter C is also marked, which is equivalent to the heat required to raise 1 000 grams of water from 14.5 degrees Celsius to 15.5 degrees Celsius at1atmospheric pressure, which is about equal to the internal energy of 4 186 joules. (1000 calories = 1 calories).
So, in fact, this can of soda contains 200,000 calories (but don't worry, it also applies to exercise-when the exercise chart says that you jog for 2 kilometers and burn 100 calories, it is 100 calories). In English, "calorie" (lowercase) means calorie, which is about 4. 186 joules, and "calorie" (uppercase) means calorie, which is about 4 186 joules.
Because scientists later found that the specific heat capacity of water is different at different temperatures, the following different definitions were derived:
Nutritional "15 degree heat": The heat required to raise 1 g water from 1 4.5℃ to 15.5℃ at1atmospheric pressure is about 4. 1855 joules by the International Committee.
"4-degree calorie": the heat required to raise 1 g of water from 3.5℃ to 4.5℃ at 1 atmospheric pressure.
"20-degree calorie": At 1 atmospheric pressure, the heat required to raise 1g water from 19.5℃ to 20.5℃ is about 4. 18 19 Joules.
"Average heat": At 1 atmospheric pressure, the average heat per degree required to raise 1g water from 0℃ to 100℃ is about 4. 190 Joules.
The heat of the international steam meter is about 4. 1868 joules.
The "thermochemical calorie" used in thermodynamics and chemistry is about 4. 184 joules.
"Nutrition and food calories": At 1 atmospheric pressure, the heat required to raise1000g of water from 14.5℃ to 15.5℃ is about 4 186 Joules.
Generally speaking, there are two kinds of calories:
Calories, also known as capital letter C, are most commonly used in food labels, which is equivalent to the heat required to raise 1 000 grams of water from 14.5℃ to 15.5℃ at1atmospheric pressure, which is about equal to the internal energy of 4 186 joules.
Xiaoka, also called cal, is equivalent to the heat required to raise 1 g water from 14.5℃ to 15.5℃ at1atmospheric pressure, which is quite common in scientific research literature. Small card = 1 big card (1 KI
Extended data:
1, Joule has been widely used as the unit of heat in modern science, and "15℃ heat" is generally used in nutrition.
2. Joules are widely used in Europe, while calories are used as the legal unit of food calories in the United States. Although Joule is also the legal unit in China, calories are still widely used because of the tradition in China.
3. The daily calorie intake of human beings is calculated by "calories", so the nutrition label generally adopts kilocalories, commonly known as calories (symbol? Kcal, sometimes writing? Cal) as the unit; 1 calorie is equal to 1000 calories, that is, 4 186 joules. (One gram of protein and sugar can produce 4 calories, and one gram of lipid can produce 9 calories. )
4, nutrition advice, with basal metabolic rate? (BMR), the average adult absorbs 1800 to 2400 calories a day, which is equivalent to 7500 to 10000 kilojoules. Too much or too little is unhealthy.
References:
Baidu encyclopedia-calories