From what I understand, kilo is used for a 1000 units of something. Like kilometer is 1000 meters, kilogram is 1000 gram and so on. But when it comes to the food we consume, when we say coconut water has 18 kilocalorie/100 gm, why does it not mean 18000 calorie in general sense?
In: Physics
Kilo calorie and calorie are not interchangeable. Kilocalorie and Calorie are. The capitalisation is important. A calorie is a very (relatively) small unit of energy, and a Calorie is a kilocalorie because we consume a large number of calories such that it’s just easier to measure in kilocalories. Then shortened it to Calories because it’s easier to say. Yes it’s confusing but it makes sense. Kind of.
We use calorie in 2 ways. One for energy (calorie) the other only used for food based energy (Calorie).
And 1 Calorie = 1000 calories.
It’s just a naming convention to make the numbers more reasonable on food labels, both in terms of size to keep track of and a reasonable degree of confidence in the measurement.
Most people never work with calories outside of the nutritional side, so it’s harmless enough, but those are technically kilocalories.
For a long time the convention was that Calories (capitalized) = kilocalories and lower cade calories was an actual calorie but that kinda went out the window with so many talking about them and not knowing the difference.
It does mean 18000 calorie. Its just that we just leave out the kilo very often when saying kilocalorie because a calorie is a very small unit of energy that doesnt have a use in everyday speech. So people started using calorie as a short for kilocalorie in everyday speech. If you would use it in a scientific setting it would just straight up be wrong.
Although the other comments are factually correct they only apply (afaik) in the United States.
In most of the world only the kcal (=kilocalorie) is used. The idea of having a “special” Calorie with a capital “C” is, quite frankly ludicrous. There is no need for this unit and – as you have so rightly pointed out – it is confusing and could even be dangerous.
A 100 gm of coconut water has 18 kcal or 18,000 calories; calories are a very small unit – thats why we measure them by the 1000.
1000 SI “calories” = 1 SI kilocalorie = 1 “food Calorie”
One SI calorie is the amount of energy required to raise 1 gram (1ml) pf water 1 degree C. Or, 1 food Calorie contains enough energy, assuming it was perfectly transferred, to raise 1L of water 1 degree C.
In the ‘regular world’, nobody ever talks about calories, it’s such a small amount of energy that it’s just not a useful measurement in most people’s lives, so we save a few syllables by just using Calories.
But in our every day lives we often deal in both meters and kilometers, grams and kilograms. So we use both terms.
For the relative handful of people in the world who need to use the lowercase calories measurement, they can use kilocalories pretty easily to keep their work clear.
It’s not at all unusual for common parlance use of words to be different than how the same words are used in specific fields/industries. Within those disciplines you typically need more specificity than the rest of the world needs, so you use words differently and more carefully.
Because Americans are idiots, and use anything but the metric system.
* 1 kcal (metric kilocalorie)
* 1000 cal (metric calorie)
* 1 Calorie (US Food Calorie)
* 4184 J (SI/Metric Joules)
All of the above values represent the same amount of energy.
* 1 cal is the amount needed to raise 1 g of water by 1 K/°C
* 1 kcal is the amount needed to raise 1 kg of water by 1 K or 1 °C
* 1 cal is the amount needed to raise 1 ml of water by 1 K or 1 °C
* 1 kcal is the amount needed to raise 1 l of water by 1 K or 1 °C
* 100 cal is the amount needed to raise 10 ml of water by 10 K or 10 °C
* 1 kcal is the amount needed to raise 100 ml of water by 10 K or 10 °C
* 10 kcal is the amount needed to raise 1 l of water by 10 K or 10 °C
You can answer the following question with this:
How long does it take to raise a pot with 5 l of water from 20 °C to 70 °C, with an electric stovetop of 1500W and an efficiency of 80%.
Hint: 1 W (Watt) = 1 J/s (Joules per second)
Does anyone actually use the smaller calories unit for anything as a regular measure of non-food energy things?
There’s the food Calorie and the scientific calorie, both of which are measurements of energy (IIRC, 1 calorie = 4.18 joules). The capital letter is important here. Same as kB is not the same as kb: 1000 kB (kilobytes) is 8 times larger than 1000 kb (kilobits)
1 Cal -> 1000 cal -> 1 kcal
1 B -> 8 b
Although the confusion is more than understandable given that there are zero character difference between Calorie and calorie, while for B (byte) and b (bit) at least the two words behind those abbreviations are different
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