Pamela S, Perryj, Age 10., Of Buckeye,. Ariz.,, for her question:
What are calories?
If you are a sensible young person, you know about the value of the foods you eat., and sooner or later you meet the word calorie. A growing girl needs more calories from her daily diet than an adult woman. The word calorie also appears in mechanics. An engineer may tell you that there are about 3 million calories in a pound of coal.
We measure temperature on a scale of degrees and temperature has something to do with heat. But heat and temperature are not quite the same. Heat is energy,, the kind of energy which sets molecules in motion and raises the temperature of an object.
The calorie is a measure of heat and energy. Science uses two calorie units. This is oonfusingf because the large calorie is 1000 times greater than the small calorie. The large calorie is used to measure the peel value in foods. This calorie power provides your body with heat and energy to move around and rebuild itself.
An apple provides about 100 calories., enough energy to climb a 1000 foot slope. The apple also provides calcium, scraps of iron and protein and valuable vitamins. When we count calories on our diet, we figure the value of these and other vital food ingredients,
The small calorie is used by chemists and other scientists, by mechanics and engineers. It is the amount of heat needed to raise the temperature of one gram of water by one centigrade degree. A thimble holds about a gram of water, and the normal temperature of your body is 37 centigrade degrees. It takes about 37 small calories to raise a thimbleful of cold water to the same temperature as your body.
Scientists use a calorimeter to measure heat energy, and their measurements must be as acourate as they can make them. The amount of heat needed to raise the temperature of water is not always the same. This depends upon whether the water to be measured is warm or cool, so scientists use a standard calorie. As a rule, they use the 15 degree calorie. This unit is the heat needed to raise the temperature of one gram of water at 14.5 degrees to 15.5 degrees. The large calorie used to measure foods is equal to 1000 15 degree calories.
Different substances need more heat or less heat to rise in temperature. A pint of water needs 30 times more heat than does a pint of mercury to reach boiling point. This is because different substances are made from different atoms and molecules, the calorimeter can be used, for example, to show that one atom of lead is about seven times larger and heavier than one atom of sulphur.