Calorie facts for kids

Quick facts for kids calorie
A 24-US-fluid-ounce (710 ml) Monster energy drink (right) with 330 large calories
General information
Unit of	energy
Symbol	cal
Conversions
1 cal in ...	... is equal to ...
SI units	4.184 J

A calorie is a way to measure energy. Think of it like a tiny fuel gauge for your body! It tells us how much energy is in food and drinks. It also shows how much energy your body uses.

There are two main types of calories. The small calorie (or gram calorie) is a scientific unit. It measures the heat needed to warm one gram of water by one degree Celsius.

The large calorie is what you usually see on food labels. This is actually 1,000 small calories, also called a kilocalorie (kcal). So, when a food label says "100 calories," it really means 100 kilocalories! This can be a bit confusing, but it's important to remember.

Scientists, especially in physics and chemistry, now mostly use a different unit for energy called the joule (J). One small calorie is about 4.184 joules. One large calorie (or kilocalorie) is about 4,184 joules.

The Story of the Calorie

The word "calorie" comes from the Latin word calor, meaning "heat." It was first used by a scientist named Nicolas Clément in the early 1800s. He used it to measure heat energy.

Over time, scientists realized they needed two different calorie units. One was the "small calorie" and the other was the "large calorie." To avoid confusion, some suggested using a capital "C" for the large Calorie.

Eventually, the joule became the official scientific unit for energy. This happened at a big meeting of scientists in 1948. Even so, the calorie is still widely used, especially when talking about food energy.

Different Ways to Define a Calorie

Scientists have defined the "small calorie" in slightly different ways over the years. This is because the exact amount of energy needed to heat water can change a tiny bit. It depends on things like the water's starting temperature and air pressure.

Today, for most scientific work, one small calorie is considered to be exactly 4.184 joules. This is called the thermochemical calorie. It helps everyone use the same measurement.

How We Use Calories

Calories in Your Food

When you look at food labels, the "calories" listed are almost always the large calories (kilocalories). These labels tell you how much energy you get from a serving of that food.

Different countries use different ways to show this energy. In North America, you'll mostly see "calories." In Europe, labels often show both "kilojoules" (kJ) and "kilocalories" (kcal). China mainly uses kilojoules.

Understanding food labels helps you make healthy choices. It lets you see how much energy you are taking in.

How Food Gives You Energy

Foods give your body energy to do everything. This includes running, studying, and even sleeping! Different types of food provide different amounts of energy.

• Fats give you about 9 large calories per gram.
• Carbohydrates (like sugars and starches) give you about 4 large calories per gram.
• Proteins also give you about 4 large calories per gram.

Knowing this helps you understand how your body uses food. It's like knowing how much fuel different types of cars need.

Managing Your Energy Intake

Your body needs a certain amount of energy each day. This amount depends on your age, size, and how active you are. Eating a balanced diet helps you get the right amount of energy.

Sometimes, people adjust what they eat to keep their bodies healthy. This might mean choosing foods with more or less energy. It's all about finding a balance that works for your body.

Calories in Science

In science classes like chemistry and physics, the term "calorie" usually means the small calorie. Scientists use it to measure energy in experiments. For example, they might measure the energy released during a chemical reaction.

However, most scientists now prefer to use the joule (J) or kilojoule (kJ) for energy measurements. The joule is the official unit of energy in the International System of Units (SI). So, while you might still see calories in some older science books, joules are more common today.

See also

In Spanish: Caloría para niños