ADULT SUPERVISION REQUIRED
Poverty Point Ovens:
Getting the Temperature Right!
The people of the Poverty Point culture made cooking balls in many different shapes and designs. Archaeologists have identified eight major types of cooking balls found at Poverty Point, as well as lots of other shapes and designs. Why would people make all of these different shaped objects to be used for the basic task of cooking in earthen ovens?
Some archaeologists have suggested that the Poverty Point people used their earth ovens much as we use our microwave ovens today. Just as we change the power level on our microwaves from defrost to full power, Poverty Point people may have changed the number and shape of the cooking balls to control the amount of heat used to cook their food.
This experiment will let you cook up some scientific results to "taste test" this hypothesis! Get ready for some really HOT stuff!
Does the shape of a cooking ball influence the way it gives off heat in an earth oven?
Loess soil and water or cooking balls made during Poverty Point Cooking Balls activity
Soil to fill terra cotta pot
4 inch diameter terra cotta pot for each student group
Heat safe thermometers
Tongs for picking up hot cooking balls
Thin colored markers
Poverty Point Cooking Balls overhead transparency
Digital watch or watch with minute hand
Oven or toaster oven
1. Look at the Poverty Point Cooking Balls transparency and choose one type of cooking ball for your group to make. Each group should choose a shape which has a different amount of surface area. Surface area is the amount of the cooking ball's outside layer that is exposed to air.
2. Add water to the soil until you have a thick "mud" mixture which can be rolled into balls. Use the scales to measure out 60 grams of mud for making each cooking ball. Each person in your group should make one cooking ball. Check your finished cooking balls by weighing them on the scales. Most cooking balls found by archaeologists weigh between 50 and 60 grams. (If your class is using the cooking balls that you made in the Poverty Point Cooking Ball activity, skip this step.)
3. Let the cooking balls dry and then weigh them again. What differences do you find in weight loss? Record your cooking balls' weights below.
4. Each group will write all of their cooking ball weights on the chalkboard. Look for a weight which all of the shapes have in common. For example, if each of the different shapes has a ball which weighs 57 grams, then this would be a good weight for everyone to use in the experiment.
5. Use the terra cotta flower pot to make your earth oven. Measure the inside of the pot from the top to the bottom with a ruler. Make a dot with a marker halfway up the side of the pot. Add dirt to the pot so that it is filled up to your dot.
6. Place the heat-safe thermometer in the pot so that the tip touches the dirt. Tape your thermometer in a vertical position along the inside of the pot so that it will not move.
7. Look carefully at all of the different shapes of Poverty Point cooking balls to be tested. Rank them in order from the shape with the MOST surface area to the shape with the LEAST surface area. Remember that surface area is the amount of the cooking ball's outside layer which is exposed to air.
|MOST SURFACE AREA:||____________________|
|LEAST SURFACE AREA:||____________________|
8. What is your "best guess" about what will happen in the experiment?
Which ball do you think will give off heat the fastest? __________________________
Which oven will stay the hottest for the longest amount of time? ___________________
How is the amount of surface area related to heat retention? _______________________
9. Draw a simple sketch of the type of your group's cooking ball above the Oven column on the Data Sheet and label it.
10. Your group will need one member to measure the temperature on the thermometer, one member to record the data on the Data Sheet, and another member to be the Time Keeper and announce when each minute has passed. Write your job assignments below:
11. YOU WILL NEED AN ADULT'S HELP ON THIS STEP! Heat the cooking ball in a hot oven or toaster oven for 30 minutes. Ask the adult to use the tongs to pick up the cooking ball and place it in the middle of the dirt in the earth oven pot.
12. Quickly add soil to the terra cotta "earth oven" until the pot is full. Read the thermometer for the earth oven and record it on your data sheet. Wait one minute and check the temperature of the pot again. Keep checking and recording the temperature of the earth oven every minute. Do this for about 30 minutes if possible.