Blubber Mania

Courtesy of National Science Foundation Polar Connections
http://www.nsf.gov/od/lpa/nstw/teach/nstw98/english/actc/blubb1.htm

MATERIALS PER 4-PERSON TEAM

• 1 blubber mitt and 1 control mitt (1 kg. of lard and 4 to 6 tall Ziploc® sandwich bags per team; see Preparation)
• samples of fabrics that might act as insulators (leather, wool, cotton, fur) and other materials such as saw dust, aluminum foil, down feathers from an old pillow or blanket, or confetti
• 2 large, steep-sided bowls or #10 tin cans
• 2 thermometers
• access to hot tap water
• access to a cooler filled with uniform ice cubes

Optional:

• additional bag of ice in a cooler (for making ice water)
• packing or duct tape

CONTEXT
In Where Did That Heat Flow Now?, students explored some of the ways heat flows. In this activity, they will discover how insulation that slows the flow of heat helps polar animals conserve body heat and live in subzero environments without freezing.

PREPARATION
The day before, prepare the ice cubes (one tray per team). For each team of students, make two mitts: an experimental mitt filled with lard and an empty control mitt (or have your students make the mitts). Here's how:

• Put the lard in a Ziploc sandwich bag.
• Turn a second bag inside out and insert it into the first bag.
• "Zip" the two bags together, trapping the fat in between them. Tape the gap on either side to make the mitt airtight.
• Put a fist inside the mitt and spread the "blubber" in an even layer.
• Use the same procedure for the control mitt, omitting the lard.

PROCEDURE

1. Begin by asking students how they might keep water from freezing in a freezer. Brainstorm ideas, including the use of insulation. What exactly does "insulate" mean? (One misconception is that insulation makes objects or people warmer. Instead, it simply reduces the flow of heat from a warmer area to a colder one by the processes you explored in Where Did That Heat Flow Now?.) Allow students to formulate their own definitions and re-examine them after the experiment. Break into teams of four and distribute the materials.
2. Blubber is a type of fat that acts as an insulator for some animals. To help demonstrate its insulating properties, do the following:
   • Instruct each team to fill a bowl with hot water and record its temperature. (Note: Let the tap water run for a few minutes so that it reaches its maximum temperature. You'll also need to refill the containers for each team of four, since the experiment itself will cause the water to cool down.) Have students take turns placing their hands in the mitts and dipping them in the water. Do they feel a difference in temperature?
   • Next, instruct teams to place one ice cube in the blubber mitt and another in the control mitt. Seal each mitt with duct tape to make it watertight, and place each one in a container of hot tap water. Wait five minutes; then have teams remove the mitts from the water, open them, and observe how much each ice cube has melted. Reseal the mitts and place them back in the water. How long does it take for each cube to melt completely? The longer a cube lasts, the better the insulation.
3. Now challenge your teams to design their own "survival suits" for polar waters. The object is to insulate themselves against freezing water temperatures. Using the mitt design, teams can substitute various types of fabric (leather, wool, cotton, or fur) for the lard to create a new kind of insulated mitt. Teams could also experiment with other materials such as sawdust, aluminum foil, down feathers from an old pillow, or confetti.
4. After teams have completed their survival suits, have them fill the containers with cold tap water and a few ice cubes (to simulate polar waters). Students can then take turns putting their hands into the control mitt and their new insulated mitt, placing them partway into the cold water, and noting how well their survival suit works as an insulator against the cold.
5. Next, instruct teams to place one cup of hot tap water into their survival suit mitt, and one cup into the control mitt. Measure and record the temperature of the water inside each mitt with the thermometer. Seal each mitt and place it in the containers of ice water. Measure and record the temperature of the water inside each mitt every 2 minutes for at least 12 minutes. The less the temperature drops, the better the insulative property of the team's survival suit. Have teams compare their results to determine which suits were the best insulators against the cold and why.

ASSESSMENT
Ask teams to evaluate their own designs based on how well they worked.

If they didn't work, how would they do them differently? How could they make this somewhat subjective experiment more scientific? Then test students' basic understanding by asking them to hypothesize why camels have thick fur on their backs, even though they live in a hot climate. (In the desert, the outside temperature is often warmer than body temperatures. Fur keeps the outer heat from penetrating the body; it's the camel's insulation against heat, instead of cold.) Ask students to come up with similar counter-intuitive examples of insulation. For example: Picture two snowmen, one wearing a fur coat, on a warm day. Which one would melt faster? Why? (The one without the fur. The fur blocks the heat on the outside from melting the snowman on the inside.)

EXTENSION
Ask: Might air be an effective insulator? How would students propose to find out? (One way: Fold bubble wrap in half and seal the sides with waterproof tape to make a snug Bubble Mitt and test with an ice cube as described above.) Animals fluff their fur or feathers to allow in air. Polar bears and Arctic foxes, in fact, have hollow hairs for buoyancy, better insulation, and absorbing the sun's energy.

Resources

Antarctica: A Guide to the Wildlife, by Tony Soper (Bradt Publications; 1996). Short informative descriptions of each major species.

Arctic Dreams: Imagination and Desire in a Northern Landscape, by Barry Lopez (Scribner's; 1986) and other polar-related books by this acclaimed nature writer. Vivid descriptions of landscape and wildlife.

Arctic Animals, The Arctic Land, Arctic Whales & Whaling, An Arctic Community, by Bobbie Kalman (Crabtree). "The Arctic World Series" for students is packed with information and photos.