CHEM.13.B

Students may make the connection between calorimetry and calories in food.  A calorie is a unit that is used to measure energy. The "Calorie" used on a food package is actually a kilocalorie, or 1,000 calories. A Calorie (kcal) is the amount of energy needed to raise the temperature of 1 kilogram of water 1 degree Celsius. So the Calorie on a food package is 1,000 times larger than the calorie used in chemistry and physics.

The original method used to determine the number of kcals in a given food directly measured the energy it produced when burned. The food was placed in a sealed container surrounded by water—an apparatus known as a bomb calorimeter. The food was completely burned and the resulting rise in water temperature was measured. While this is not used today to determine the energy content of food, it is used in chemistry labs to compare the amount of energy in various substances.