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The workings of the body's thermostat become clear when kids measure their skin temperature
To a certain extent, the human body functions like a biological furnace. The body chemically breaks down the fuels of carbohydrates, fats and proteins and releases their energy. This process is called cellular respiration. By releasing heat to the environment, the body maintains the relatively constant internal temperature necessary for survival.
The amount of heat loss is determined mostly by the amount of blood supplied to tissues just beneath the skin. When there's too much heat in the body, the blood supply to the surface tissues increases, allowing excess heat to escape. When there isn't enough heat to balance the body's losses, the blood supply to the surface tissues decreases and conserves the body's core temperature. Even though the human body is constantly circulating blood, "thin" parts of the body lose heat to the environment much faster than do "thicker" parts of the body.
Here's an activity that takes approximately an hour, and shows kids that the body's surface temperature can vary from body part to body part. You'll need enough strip thermometers to give one to each two- to three-person group of students, as well as liquid bleach, a plastic bucket, water and paper towels.
Start by disinfecting the strip thermometers. To do this, add one capful (one tsp) of bleach to one liter (32 oz) of water (do not use hot water) in a bucket. (Do not use solvents such as alcohol or acetone or the strips will be destroyed.) Dip a...