Science Experiments You Can Eat by Vicki Cobb

Author:Vicki Cobb
Language: eng
Format: epub, azw3
Publisher: HarperCollins
Published: 2016-05-25T16:00:00+00:00

CHAPTER 7

PLANTS WE EAT

All living things need a constant supply of energy in order to stay alive. The source of this energy is food combining with oxygen. The oxidation of food (sugar is an example) is the same basic overall reaction as that of fuel combining with oxygen to produce a fire. (There is, of course, a big difference that I’ll tell you about in a minute.) Here’s an equation that shows the similarity between the reactions:

sugar (fuel) + oxygen → carbon dioxide + water + energy (fire)

When a fuel burns, the released energy is rapid and uncontrolled. In living things, there are many steps in the oxidation of food, and the energy is released in a carefully controlled manner so that it can be used for the various activities of living.

Scientists can measure the amount of energy that can be released from different kinds of food as heat energy. They put preweighed amounts of food in a special instrument called a calorimeter. The food is burned with oxygen, and the heat energy given off by the reaction raises the temperature of the water outside the chamber where the food is burning. The change in the temperature of the water is a measure of the amount of energy in the food. This heat is measured in calories. If you look in most general cookbooks, you can find a table that lists the calories in different foods. Fats have the most calories and proteins have the least. (You can find instructions for building your own calorimeter here.)

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