By Morgan Turano, science editor
Part 1
Have you ever opened a car door on a hot summer day? You may have noticed that inside the car was hotter than outside the car. In fact, inside a closed car can get much hotter than it is outside. On a sunny day the inside of a car can reach 110°F, even when it is only 70°F outside!
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| If you want to help your child, use our version for guardians. |
Sometimes on sunny days, people will put Sun visors in the front windshield. This reflects sunlight away from the car. Some people will leave the windows down. This allows the hot air to escape. Both actions have the same effect. They help reduce the temperature inside the car. Clouds can change the temperature inside a car too. When it is cloudy, the temperature inside a car is about 10°F cooler.But what if you wanted to raise the temperature? Could you make a simple device that would get so hot inside that you could use it to cook food?
WANT TO HELP YOUR STUDENT?: Victory has created a guardian version of this lesson so that parents and guardians can provide guidance | A printable version of this lesson is also available
Design
You want to design a simple device that will get hot enough to cook food. You can base your device on what you noticed about cars in the summertime. The design for the solar cooker should have the same features that made the car hot inside. It should also be made from materials you already have around your home.
Let’s think about the car on the hot day. The car had all its doors and windows closed, so no hot air could escape. Opening the windows made the temperature lower. The solar cooker should be able to close to keep the hot air inside. You can use a cardboard box with a lid.
The car had clear windows, which allowed sunlight to come inside. Blocking the sunlight with clouds or a Sun visor made the temperature lower. The solar cooker should have clear windows to let the sunlight in. You can use plastic wrap to make a window to let the sunlight in.
Materials
- Cardboard box (like a shoebox or pizza box)
- Pencil
- Ruler
- Scissors
- Plastic wrap
- Duct tape (or other tape, glue, or staples)
- Thermometer
- Chocolate (or other meltable food such as cheese)
- Paper plate
- Paper or piece of cardboard
Construction
| To make the solar cooker, first you need a cardboard box, like a pizza box or a shoebox with a lid.
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| A. Draw a square on the lid that is nearly as big as the whole top. Use a ruler to make your lines straight.
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| B. Ask an adult to help you cut a square flap in the lid of the box by cutting three sides of the square that you drew.
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| C. Fold up the fourth side of the flap, so that you can open and close it. If you need help, ask an adult.
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| D. Open the lid of the solar cooker.
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| E. Get a piece of plastic wrap that is a little bigger than the opening cut in the lid. |  |
| G. Place the plastic wrap over the hole so that it is flat. Stick it in place with duct tape all around the edge.
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| H. Close the lid and open the flap.
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| I. Have an adult use a pencil or scissors to poke a hole through the front of the solar cooker. The hole should be big enough to push the end of the thermometer into the cooker. |  |
| J. Make a flap using cardboard or paper to cover the hole when you are not taking the temperature. Tape your flap in place. Your cooker is complete! |  |
Part 2
Experiment A: In the Dark
You built the solar cooker with clear plastic-wrap windows to let the sunlight in. You did this because the light is transferring energy from the sun to the inside of the cooker. But how can you prove this? You can have two tests. In the first test, you can measure the temperature differences when the solar cooker is left in the dark for a half hour. Then, you can measure the temperature differences when the solar cooker is left in the sunlight for a half hour.
Solar cookers can become very hot. Always ask an adult to handle and open the solar cooker for you.
Now that the solar cooker is built, you will want to test it. First, you will test it to see if it will work without sunlight.
- Step 1. Place your solar cooker in a dark location, like inside a closet in your home.
- Step 2. Open the lid of the solar cooker. Place the paper plate inside the solar cooker, and put a piece of the food on the plate. Record the appearance of your food.
- Step 3. Close the lid and make sure the window flap is open. Measure the temperature inside the solar cooker using the hole at the front of the cooker and record it in the table.
- Step 4. Record the temperature in the area near your solar cooker on your data sheet below.
- Step 5. After a half hour, check the temperature in the area and inside the solar cooker using the hole in the front, and check the appearance of your food.
Experiment A: In the Dark Data
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Starting |
After 1/2 Hour |
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Temperature in Area (°F) |
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Temperature in Solar Cooker (°F) |
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Appearance of Food |
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- Did the temperature change in the area during the half hour? How much did it change?
- Did the temperature change in the solar cooker during the half hour? How much did it change?
- Which change in temperature was greater? The change in the area or the change in the solar cooker? Or were they the same?
- To make sure that the temperature of the area doesn’t affect our results, let’s subtract the temperature in the area from the temperature in the cooker:
_____________________ °F – ___________________°F = _______________ °F
Starting Temperature in Cooker – Starting Temperature in Area = Adjusted Starting Temperature
_____________________ °F – _________________ °F = _______________ °F
After 1/2 Hour Temperature in Cooker – After 1/2 Hour Temperature in Area = Adjusted Final Temperature
- Did the appearance of the food change? Why or why not?
Part 3
Experiment B: In the Sunlight
You measured the temperature before and after the solar cooker was left in the dark for a half hour. Now, you can measure the temperature differences when the solar cooker is left in the sunlight for a half hour.
Remember, solar cookers can become very hot. Always ask an adult to handle and open the solar cooker for you.
- Step 1. Place your solar cooker in full sunshine. Make sure the solar cooker is facing the Sun so that the light is shining through the plastic wrap window.
- Step 2. Open the lid of the solar cooker. Place the paper plate inside the solar cooker and put a piece of the food on the plate. Record the appearance of your food.
- Step 3. Close the lid and make sure the window flap is open and that the sunlight is shining through the plastic wrap window onto the food. Measure the temperature inside the solar cooker using the hole at the front of the cooker and record it in the table.
- Step 4. Record the temperature in the area near your solar cooker on your data sheet below.
- Step 5. After a half hour, check the temperature in the area and inside the solar cooker using the hole in the front, and check the appearance of your food.
Experiment B: In the Sunlight Data
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Starting |
After 1/2 Hour |
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Temperature in Area (°F) |
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Temperature in Solar Cooker (°F) |
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Appearance of Food |
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- Did the temperature change in the area during the half hour? How much did it change?
- Did the temperature change in the solar cooker during the half hour? How much did it change?
- Which change in temperature was greater? The change in the area or the change in the solar cooker? Or were they the same?
- To make sure that the temperature of the area doesn’t affect our results, let’s subtract the temperature in the area from the temperature in the cooker:
_____________________ °F – ___________________°F = _______________ °F
Starting Temperature in Cooker – Starting Temperature in Area = Adjusted Starting Temperature
____________________ °F – _________________ °F = _______________ °F
After 1/2 Hour Temperature in Cooker – After 1/2 Hour Temperature in Area = Adjusted Final Temperature
- Did the appearance of the food change? Why or why not?
Analyzing the Data
How can you tell if sunlight affected the temperature inside the solar cooker? You can compare the data from our two tests.
- Look at your data tables. Which was hotter, the solar cooker after a half hour in the dark or a half hour in the sunlight?
- Look at the change in temperature inside the solar cooker (question 2 of each experiment). Which had a greater change, the experiment in the dark or in the sunlight?
- Look at the adjusted temperatures inside the solar cooker after each experiment (question 4 of each experiment). Which was hotter, the solar cooker after a half hour in the dark or in the sunlight?
- Look at the adjusted temperatures inside the solar cooker before and after each experiment (question 4 of each experiment). Which had a greater change, the experiment in the dark or in the sunlight?
- Do you think that the sunlight affected the temperature inside the solar cooker? Why or why not?
- Complete the sentence below using one of these terms: electrical current, light, sound.
Energy was transferred by _____________ from the Sun into the solar cooker, increasing the temperature.
Part 4
Improving the Design
Think about what you know about sunlight, heat, and how the solar cooker works.
Would increasing the amount of sunlight affect how well your solar cooker works? How could you accomplish this? Think about what materials you have around your house that you could use to reflect sunlight into the solar cooker. For instance, you could add aluminum foil to the underside of the flap to help direct sunlight into the plastic-wrap window.
Would changing the color inside the solar cooker affect how well your solar cooker works? How could you accomplish this? Think about wearing clothes on a hot day. For instance, maybe you’ve noticed that you feel hotter when you wear a black T-shirt in the sun than when you wear a white one. You could add dark construction paper to the inside of the solar cooker to help hold the heat in.
Try modifying your device by making each of these changes, and run the Experiment B (in the sunlight) again for each change. Which modification increased the temperature inside the solar cooker the most? What happens if you make both modifications at once?
Once you have found the best design, you can use your solar cooker to make s’mores! All you need is graham crackers, marshmallows, chocolate, and an adult’s supervision.