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Physical Science: Session 4

A Closer Look: Where Does the "Weight" Go?

cheese candle
"Cheese" candle.

Is burning a candle a good analogy for what happens to food inside the body? During the video, Robin and Sallie, our hosts, burned a “cheese” candle as a possible model for what happens to food inside our bodies. Although it is true that food is essentially the fuel for our bodies, the process by which we extract energy from it is different than the process by which a candle burns.

When a wax candle is burning, its particles, made mostly of carbon and hydrogen atoms, combine with oxygen in the air to produce carbon dioxide and water vapor. In addition, some energy is released in the form of heat. (We’ll learn more about heat in Session 7.)

However, our bodies do not “burn” particles of food in a single reaction like the burning candle). Instead, a series of reactions takes place during which the result of one reaction becomes the input to the next. Food is broken down into simple sugars made mostly of carbon, nitrogen, oxygen, and hydrogen molecules that are then combined with the oxygen we breathe. Along the way, other molecules (called enzymes) help the reactions occur.

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