calorie-The unit of energy required to raise one gram of water through one degree centrigrade. Think of the calorie this way.. You have a little thimble-full of water. This water is 20 degrees celsius. Let's say that you want to raise the temperature of this water to 21 degrees celsius. You would be raising the temperature of the water from 20 to 21 degrees celsius, which is a difference of only 1 degree. Well, we need some form of energy to raise the temperature don't we? It's like placing the water on the stove, and turning the flame on to heat it. The flame comes from burning gas on the stove. If it's electric,then electricity had to be generated. In the end, energy is required to heat that water up. Believe it or not, we can get the energy needed to heat the water from burning fat or sugar (or even other substances, but we won't go into that) ! The energy released from burning the fat or sugar will heat the water. So, if we burn sugar until the water reaches 21 degrees, then we simply weigh the remaining sugar, and we will know how much we burned to heat the water. For example, if we burned one gram of sugar to raise the water temperature 1 degree, then we say that 1 gram of a particular type of sugar has 1 calorie of energy. That's all there is to it.A kilocalorie is a term which means a large calorie. We use this term because in actual fact, a calorie is very small. A larger unit was needed, so we invented the term "kilocalorie". Kilo means 1000. Therefore, a kilocalorie is 1000 calories. We also call the kilocalorie the "large calorie". We use the kilocalorie to measure the energy values of food.