Calories are units of energy. We often associate calories with food, but in fact they apply to any substance that contains energy.

Simply put, 1 calorie of energy or heat can raise the temperature of 1 gram of water by 1 degree Celsius at one atmospheric pressure. 1 calorie is approximately equal to 4. 186 joules (joules are commonly used units of energy in physics).

Most of us 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, actually, 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 to 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.

Extended data:

I. Correlation transformation

"4-degree calorie": the heat required to raise 1 gram 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.

Second, the demand for heat.

Daily calorie requirement of adults = basic calorie required for basic metabolism of human body+calorie required for physical activity+calorie required for digestion of food.

Heat required for digesting food = 10% x (minimum heat required for basic metabolism of human body+heat required for physical activity)

Daily caloric requirement of adults = 1. 1 x (minimum basal caloric requirement for basic metabolism of human body+caloric requirement for physical activity).

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