Hairy, Fat and Warm

Research Questions:

• How does hair keep an animal warm?
• Does the layer of fat underneath an animal’s skin keep it warm?

Hair—fur—helps mammals maintain a stable core body temperature and inhabit a wide range of environments from deserts to the artic. The amount of fur reflects the environment and the animal’s adaptation to the conditions. Likewise, feathers provide birds with insulation, and scientists believe that the protection of body warmth was the primary driver in the evolution of feathers.

Chemically speaking, fats are triglycerides that belong to a diverse class of molecules called lipids.Triglycerides are generally insoluble in water though highly soluble in organic substances.Triglycerides make efficient stores of warmth, because of the low rate of heat transfer in fat.This layer also cushions organs and absorbs a range of vitamins.

Materials:

• 1-quart (1 liter) jars with lids
• Box that measures at least 2 inches taller than the jars
• 7-ounce paper cups
• Cotton balls
• A large sock
• Crisco or other thick shortening
• Cooking oil
• Measuring cup
• Water
• Thermometers

Experimental Procedure

1. Cover the bottom of a box with cotton balls.
2. Set a jar in the box and fill in cotton balls all around it.
3. Line up three jars and fill each with 2 cups of warm water.
4. Record the temperature of the water in each jar.
5. Seal the jars with lids.
6. Cover one of the jars with a sock.
7. Wait 10 minutes, uncover the jars and record the temperatures again.
8. Repeat at selected intervals a few times to compare the loss of heat over time.
9. Fill several cups with varying thickness of shortening—thinning the Crisco with vegetable oil.
10. Label the cups.
11. Record the temperature of the shortening in each cup.
12. Place the cups in the freezer.
13. Wait 5 minutes and record the temperatures again.
14. Repeat every 5 minutes until 30 minutes has passed.

[NOTE: Students can be very creative testing a variety of insulation materials against each other: wool scarves, wool yarn, cotton socks, feathers, canola oil, corn oil, etc.]

Line graphs can visually display the plethora of data generated from this experiment:

Terms/Concepts: Heat conduction; Insulation

References:

• Amazing Birds, Brenda Williams (2007).
• 1000 Things You Should Know about Mammals, Steve Parker and Belinda Gallagher (2006).