Lesson # 4
Maintaining Body Heat (Science )
Students will observe and compare heat loss in different objects with surface area-to-volume ratios (see Teacher Background for more information). Students will be able to transfer this comparison to the physical characteristics of animals in their environment.
- Hot and cold water from tap
- Large Styrofoam cup with lid
- 2 plastic Ziploc sandwich bags
- Bucket, large bowl, or dishpan
- 1 rubber disposable glove
- Timer or watch
The glove is similar to mammals with long legs, lots of surface area but little volume. Consider what would happen if a whale had legs. It would loose its body heat like the glove, and quickly cool in the ocean. The plain sandwich bag proves that having no legs helps sea mammals maintain the warm body temperature. But the warmest bag from inside the cup proves what good insulation (like blubber) can do for ocean mammals. The bag inside the cup is the whale with no legs, and the Styrofoam cup is the whale's insulating blubber layer.
But what about those mammals that live in relatively warm oceans? Or don't whales ever get hot? Ask your students when they get hot while sleeping at night what they do. Some may answer they stick one foot out of the covers. Why? Because the temperature of the foot will cool because the surrounding temperature is cooler than under the covers. Whale flippers do almost the same thing, but this is not why they flip them above the water. There is less blubber on the whale's flipper, and it can conduct body heat to the surrounding cooler ocean better than the rest of its body. Thereby, cooling off.
- Divide the class into groups of four. Each group needs to have all of the above materials.
- Assign each student a role.
Fill bucket half-full of cold water. This will be used to represent the ocean.
Put hot water in the glove, filling the fingers and in both sandwich bags, trying to put the same amount of water in each. Tie off the glove and close the Ziploc bags.
Feel each bag and glove, have students record observations in question 1 of the Lab Worksheet. They should feel the same.
Put one of the Ziploc bags into the Styrofoam cup, and place the lid on it.
Place the glove, bag, and Styrofoam cup with bag into the bucket of cold water.
After 5 minutes, remove the glove, bag, and Styrofoam cup with bag from the bucket. Feel all three again, have students record observations in question 3 of the Lab Worksheet. The glove is the coolest and the bag from the cup is the warmest.
Choose one member from each group to share their results with the class. Use the background information for class discussion.
- Materials - to collect and maintain materials needed for lab.
- Recorder - to record information from lab on the Lab Worksheet.
- Technician - to perform maneuvering of lab work.
- Maintenance - to clean up the lab station and be prepared for spills (can be combined with materials as one role for odd numbered groups).
Students will successfully complete the activity. Students will verbally and hand write answers to questions asked regarding the activity.
- How do the bags feel before they are placed into the cold "ocean"?
- What do you think the temperatures of the glove and bags will be like after 5 minutes in the cold "ocean"? Why?
- What did the glove and two bags feel like after they were taken out of the "ocean"?
- Why do you think the three bags felt different?
- Which one represented a whale? Why?