The Relationship Between Calories and Heat: How are calories and heat related?

[Raza]

What really is a calorie?
Are calories actually burned?
Why is this terminology used?
What are the relationship among a calorie to measure food energy, a calorie to measure heat?

 

[DaveC426913]

A calorie is a unit of energy. 1 calorie of energy will raise 1 gram of water 1 degree C.

Calories aren't burned, but chemical processes usually involve oxidation, which is a slow burn, which is what is measured by the calorie.

The food calorie is actually a KCal. (the amount of energy to raise 1 kg of water by 1 degree) i.e. 1 food calorie is equivalent to 1000 calories.

These days, in the science world (though not in the nutrition world) the calorie is deprecated. The Joule is more common usage. 1 calorie is 4.185 Joules.

 

[Mattara]

According to Google calculator 1 calorie = 1/0.239005736 Joule which would make it closer to 4.184 (4,18400000...) Joules.

 

[Astronuc]

Getting nitpicky ( ) -

The Fifth International Conference on the Properties of Steam (London, July 1956) defined the International Table calorie as 4.1868 J. Therefore the exact conversion factor for the International Table Btu is 1.055 055 852 62 kJ. Note that the notation for International Table used in this listing is subscript "IT." Similarily, the notation for thermochemical is subscript "th." Further, the thermochemical Btu, Btu_th, is based on the thermochemical calorie, cal_th, where cal_th = 4.184 J exactly.

- http://physics.nist.gov/Pubs/SP811/footnotes.html#f11

http://physics.nist.gov/Pubs/SP811/appenB9.html#HEAT - conversions for units of heat (energy)