The Three Bears Heat Investigation--It's Just Right

Denise M. Gerdes
St. Croix Prep Academy, Stillwater, MN
Personally developed activity

Summary

This activity uses the story of the three bears as a way to investigate conduction, convection, radiation and insulation properties. It also could be used to describe the laws of thermodynamics and conservation of energy.

Learning Goals

Objectives:
Students will be able to:
1. Explain why Baby Bear's bowl of porridge could not have been "just right" and/or design a plan to make it just right. Baby Bear's bowl must still contain the least amount of porridge.
2. Explain what material Mama Bear's bowl of porridge was made of to make it "too cold and/or design a plan to make Mama's Bears porridge too cold. Mama Bear's bowl must still contain the medium amount of porridge between the three bears.
3. Explain why Papa Bear's bowl was too hot. Papa Bear still has the same amount of porridge.
4. Describe 3 ways heat moves through matter and what materials conduct heat better than others.

Context for Use

Class size of 30 6-8 graders. Could also be modified for 9-12 graders. Can be easily adapted for inquiry as opposed to guided inquiry. You could begin your unit with this activity if you wish.
Time: Depending on how this experiment is conducted either through complete inquiry or through guided inquiry time will change. Between 50-100 minutes

Preparation of Students for Lesson:
Students will have learned about heat doing a variety of experiments and other differential learning techniques. They will be able to describe what heat and temperature is and how it relates to everyday life. Students will already understand conduction, radiation, convection and insulation. Students have also discovered what absolute zero means.
Heat always moves from matter that is warmer to matter that is cooler.

Description and Teaching Materials

Materials Needed:
-Ceramic cup (one for each student group)
-Styrofoam cup (one for each student group)
-Metal cup (one for each student group)
-One large plastic bowl
-One medium metal bowl
-Several small Styrofoam bowls
-Enough oatmeal, hot chocolate (and hot water) for the class
-Several thermometers (at least three per student group)
-Brown sugar (optional)
Procedure:
Tell the story of the three bears. Ask the students, from what they already learned about heat, could there be any way that Baby Bear's bowl was just right. Have the students conduct an experiment to find out how Baby Bear's bowl could have been just right. (The teacher could dress up like Goldilocks if he/she wishes). Tell the students that there is another component
you are adding to the dilemma (I add this to the embellished story), that of hot chocolate. What cup would make the hot chocolate "just right?" Tell the students they may eat the porridge (oatmeal) and drink the hot chocolate after all the experiments are completed.

Divide the students into groups of four. At each table place a metal cup, Styrofoam cup, and ceramic cup. Teacher has prepared hot chocolate ahead of time and has hot water also prepared for making oatmeal. Teacher can pour the hot chocolate into each cup or have students collect it themselves-be careful because the metal cup can burn hands! if not handled properly. Student should place a thermometer into each cup and record the temperature. Thermometers should then remain in the cups while porridge temperatures are being taken. (They can also put their hands around the cups to get a feel of the temperature---but NOT the metal cup) The table underneath each cup will be felt after a few minutes as well.

Students should make predictions about what they believe will happen to the temperature of each cup and each bowl of porridge.

Meanwhile the teacher has prepared the oatmeal in the front of the classroom. Some of the oatmeal will be put in a medium sized metal bowl-Mama Bears bowl. A large ceramic bowl (a large plastic bowl works as well) filled with A LOT of oatmeal,--Papa Bear has a big appetite--and a small Styrofoam bowl-Baby Bear's bowl. You can also use three bowls of different sizes, but made of the same material to show that Baby Bear's bowl would get coldest, fastest. The former lets students see the difference. The latter lets them see what happens in the story. I usually give a small Styrofoam bowl to each group so they can have their own porridge at their table. Thermometers should be stuck into each bowl-in the center.

After 5 minutes all temperatures in every container and cup should be recorded. This could be done three consecutive times. Depending on time each student or group of students could design a graph. This could also be done as a class with the teacher on the next day or assigned as homework.

Students should discover that the metal bowl and metal cup will lose heat the fastest because metal is a great conductor of heat. It also radiates heat better. Consequently, the only way Mama Bear's bowl could have been too cold is it would have had to have been in a metal bowl. Baby Bears bowl would be just right if it were in a Styrofoam bowl, or some other insulated type of material. Papa Bear's bowl would remain too hot because there was so much of it that the porridge insulates itself and loses heat much slower.

Are there other materials the bear family could have used to keep all their food at the same temperature? What would have happened in real life if they all would have used the same size bowls and the same type of material. What about varying the amount of food in each bowl? Why did McDonalds get sued for using coffee that was too hot and putting it in a Styrofoam cup-their coffee is no longer allowed to be hotter than a certain temperature. Why do many who camp use metal cups even thought their drinks get cooler much quicker? What would have happened if Mama Bear didn't dish up the porridge before they left? Why does a metal spoon get so hot if you leave it in a bowl of hot soup and a plastic or wood one does not? Would a metal spoon left in soup cool down the soup quicker? Why or How? Why do we use oven mitts? Tell me about metal buildings and wood buildings-sometimes metal buildings are cooler than wood buildings...... What does insulation have to do with it? What about outside temperature?

Finish with food and drink
Clean up.

Teaching Notes and Tips

Make sure that you you tell students that the metal cups get HOT!! It can burn students. Use of towel, or oven glove type mitt will work. Have students feel the table underneath all the table to feel the heat differences. This is a better way to discuss convection and conduction than using water, etc.

Assessment

Students can rewrite the story of the three bears using the new information.

Standards

Standard: 6.II.C.2 Physical Science: the student will recognize that heat is transferred by convection, conduction, and radiation from warmer objects to cooler objects until both reach the same temperature.
Could also cover parts of 8.III.B.1. The student will define conduction, convection, and radiation and explain their effects on weather and climate.
Could cover parts of 9-12 Energy transformations. 9.II.C.5. The student will be able to describe physical and chemical changes in terms of the laws of conservation of energy

References and Resources