Teaching Tips

Teaching Tips:The Insulation Experiment

Synopsis: In this module students use a simulation to investigate how heat moves through different substances commonly found in the human body. The students measure the transfer of heat through fats, bones, muscles, skin, and hair to determine which material provides organisms facing cold temperatures the best insulating layer to retain body heat.

Big Ideas:
a. Conductors allow heat to easily move through a material.
b. Insulators resist heat from easily moving through a material.
c. Animals that live in cold climates have thick layers of fat that act as insulators to reduce heat lose to their environment.
d. Certain biological adaptations enhance the survival of a species.

Misconceptions Addressed:
a. Heat is a substance.
b. Heat is not energy.
c. Objects that become readily warm do not readily become cold.
d. Temperature is a property of a particular material or object.

NSES Grades 5 – 8 Content Standards Addressed:
a. Life Science
i. Regulation and behavior
ii. Diversity and adaptation of organisms
i. Populations and ecosystems
b. Physical Science
i. Properties and changes of properties in matter
ii. Transfer of energy

Here are explanations from the methodology section that you may find useful as class discussion topics:

How do animals regulate their temperature?

The body temperature of a cold-blooded animal, called ectotherms, changes with the temperature of its environment. An endotherm, called a warm-blooded animal, maintains a fairly constant body temperature. To keep this constant body temperature warm-blooded animals must increase heat loss from its body in hot weather and decrease heat loss in cold temperatures. Bathing or standing in cold water increases the heat loss because water conducts heat faster than air.

Animals have other ways to control the movement of heat from their bodies. A part of the brain, called the hypothalamus, can change the size of small arteries near the surface of the body. The hypothalamus signals the walls of the arteries to constrict or relax. Changing the size of the arteries that carry blood can increase or decrease heat loss. Widening the arteries increases blood flow and increases heat loss. Reducing the size of the arteries decreases heat loss.

What is fat?

Fat tissue contains cells that have large droplets of fat stored inside the cells. Cells can burn the fats when the cell needs energy to do certain functions. In fact, fats have about two times as much energy as proteins or carbohydrates. Animal fats, like lard, are in the solid phase at room temperature.

Polar bear anatomy

Polar bears have a unique anatomy that provides many adaptations for the harsh environment they live in. Polar bears have three to four inches of fat below their skin on their rumps and back. This fat acts as a layer of insulation to reduce heat loss through their skin. Their skin and fur create a unique form of heat transmission. Although their fur is white to yellow in color, polar bear skin is dark. Their skin is one of the best ultraviolet light absorbers found in nature. Even on overcast days, ultraviolet light can penetrate clouds and be absorbed by the bear's skin. The hairs that make up their fur are also great heat-catching devices. Each hair is hollow at the center and acts as a light trap that directs light to the bear's skin. The density and oily nature of the hairs prevents moisture from penetrating to the skin. The hairs also have a springy quality that resists compaction and provide an insulated barrier of air around the bear's skin. Lastly, polar bears have a long snout that warms the cool air it inhales.

What is wind chill?

Have you ever noticed that you feel colder on a windy winter day than on a calm winter day with an identical temperature? The wind chill factor describes how fast body heat is lost based on temperature and wind speed. The greater the wind speed, the faster you lose body heat and the colder you feel.

You can do a simple experiment to help you understand the concept of wind chill. Touch a piece of paper and note its temperature. Next, find a piece of metal in the same room, like on your desk, and touch it. The metal feels colder although both the paper and metal are at the same temperature. The metal moves heat away from your hand faster than the paper so it feels colder than the paper. When you're exposed to a high wind on a cold day the wind moves heat away from your body faster, so you feel colder.

Additonal Topics

Fat as an insulator in humans

Most students think of insulation as insulating us from harsh environments, but body fat not only insulates us from cold weather, it also prevents our internal body heat from escaping in cold climates. Our skin also protects us from threats beyond weather. For example, cholesterol helps protect us from (not too harsh) chemicals and strong detergents by forming a protective barrier. The fat barrier also prevent us from dehydrating too rapidly. Fat doesn't conduct heat very well, which helps explain why it doesn't allow heat and cold in and out of the body.

Cold Temperatures and You

When the body is exposed to cold temperatures, it produces to physiological responses: it increases the production of body heat, and it constricts the blood vessels in the skin. The constriction of blood vessels makes the skin a better insulator. These efforts, however, inhibit muscle functioning and make the body tire more easily. High calorie meals and plenty of water (not alchol) help with heat production and keeping warm, as do layers of dry clothes..