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GRADES 4-8
HYPOTHESIZE THIS!
OBJECTIVE
The student will be able to predict, measure, collect, and analyze data to investigate heat loss in water and in air.
MATERIALS
Each class needs
•

smooth peanut butter
• crock pot
•

large spoon or ladle
Each student group needs
• 1 pan or bowl of water at room temperature
•

4 sturdy paper coffee cups
• 2 thermometers
•

2 popsicle sticks
• tape
•

pencils
• paper
 

BACKGROUND

Scientists explore our world by objectively testing hypotheses using the scientific method: define the problem/ask a question, collect background information, formulate a hypothesis, test the hypothesis, make and record observations, and draw conclusions.
In this exercise, your students are laboratory scientists. You have gathered the following information from field scientists observing walruses in Alaska: a walrus' core body temperature is about 36.6° C (about the same as a human's). From about -20° C to 15° C (air temperature), temperature doesn't seem to affect walrus behavior. They can withstand even cooler temperatures and have been observed at -31° C. When temperatures rise above 15° C, walruses often stay in the water. The Alaska field scientists need your help. They want to know if walruses stay warmer in water or in air - in which environment might they lose more body heat?
 
For a quick look at walrus information, visit the Walrus Animal Byte.
For in-depth information on walruses, visit the Walrus InfoBook.
 
 

ACTION
1. Divide the class into cooperative learning groups. Distribute materials.
   
2.

Students predict whether heat loss occurs faster in water or air. They state a testable hypothesis (For example: "Heat loss occurs faster in water than it does in air.") They use the following experiment to test their hypothesis. Groups report their results.
   
3.

First, students measure the water temperature in their pans of water. Add warm butter or ice to bring the water to the same temperature as the air. Heat peanut butter in a crock pot to a temperature of about 80-90° C. Place a spoon in the warmed pot. Students tape popsicle sticks to thermometers so that one end of the stick extends slightly past the thermometer bulb (don't tape the bulb). This technique will help students stir without the thermometer bulb touching the bottom or sides of the cup.
   
4.

Each student group spoons equal amounts of warmed peanut butter into two paper coffee cups (fill about halfway). Place a thermometer in each cup. One student in each group holds one cup of peanut butter in the pan of water (but don't touch the bottom of the pan!). Another student holds the other cup in air. Students use thermometers to continuously stir the peanut butter in each cup to ensure a uniform temperature throughout. A third student in each group records temperatures at 30-second intervals, for at least 5 minutes. Students analyze results and answer the following questions:
•

Does heat loss occur faster in water or in air? Is your hypothesis still viable?
°

Create a graph to display your results.
• Evaluate the testing procedures. Were they effective? How could they be improved
• Can you design a different experiment to test your hypothesis?
• How might the results of your investigation help field scientists studying walruses?
   
5.

Repeat experiment as time allows. Vary the experiment by adding environmental factors such as wind chill - turn a fan on the cup in air. Or, cool the pan of water.
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SOURCE MATERIAL
This classroom activity is adapted from the Walrus Teacher's Guide. While select guides are available directly within the pages of ANIMALS (see TEACHER GUIDES), the totality of our Teacher Guides are available for purchase via our catalog or education e-store.
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