Design Challenge: Making a Solar Oven

What You Need:

• Cardboard pizza box
• Box cutter or scissors
• Aluminum foil
• Plastic wrap
• Black construction paper
• Ruler
• S’mores ingredients: graham crackers, marshmallows, and chocolate
• A variety of household items that your child could potentially use to construct their device (e.g., newspaper, wooden skewers)
• Plate (preferably glass or dark-colored)
• Oven mitts
• Pen and paper for taking notes

What You Do:

1. First, explain to the design challenge to your child. Tell them that their job is to create a solar oven out of a cardboard pizza box in order to cook s'mores.
2. Ask your child the following questions so that they begin thinking critically about the design process:
   1. What does your oven need in order to cook the s'mores? (Answer: heat)
   2. What are some of the best objects or colors that absorb heat? (Answer: The color black is good at absorbing heat.)
3. Show your child the materials they have to choose from, but don't let them start building just yet. Instead, ask them to brainstorm how they will use these materials in order to create a solar oven. Have them write out or draw their ideas on a piece of paper.
4. After your child has finished brainstorming, ask them to choose the design they think will work best. Remind them of the purpose of their oven: to cook s'mores.
   1. This is an important step of the design thinking process because it teaches your child to prioritize the functionality of their design over personal preferences, and it prevents them from getting too emotionally attached to one design.
5. Once your child has decided on a design, they can start prototyping (building). Be sure to supervise and help out as needed.
6. After your child is done building, it's time to test their prototype! The best time to use your solar oven is between 11 a.m. and 2 p.m. when the sun's rays are strongest. Make sure to set the food on a dish (preferably glass or dark-colored) so you don't make a mess inside the oven.
   1. To make a solar s'more: Place one or two marshmallows on top of a graham cracker. Put two to three squares of chocolate on top of the marshmallow. Wait until the chocolate and marshmallow are done cooking to top them with the second graham cracker.
   2. Ask your child why it might be a good idea to have the chocolate on top. (Answer: Dark colors, like brown or black, are best at absorbing heat. If the chocolate is on top, it will absorb heat into the entire s'more.)
7. Wait for your child's oven to cook the food. Timing will vary depending on the oven. Be sure to frequently check back on the oven and observe whether the food is gradually cooking.
   1. If your child's oven eventually cooks the food, congratulate your child on their success!
   2. If your child's oven doesn't work, help them find out what went wrong. Then, encourage your child to go back and repeat this process until they make an oven that works.
   3. Use oven mitts to remove dishes from the oven—contents may be hot!

Here is a procedure for creating a solar oven in case your child is struggling to come up with designs:

1. Take an empty pizza box and clean out any stray bits of cheese, sauce, or crumbs.
2. Using a ruler and pencil, draw a square that is one inch from the edges of the top of the box.
3. Use a box cutter or knife to cut out three of the four sides of the square, leaving the crease-side of the box attached.
4. Make a crease along the uncut side of the square to create a flap that stands up.
5. Cut a piece of aluminum foil that is large enough to cover the inner side of the cardboard flap.
6. Wrap the foil tightly and secure with tape.
   1. Ask your child what they think the purpose of the foil is. (Answer: Aluminum foil reflects sunlight and brings heat into the oven.)
7. Line the bottom of the pizza box with black construction paper.
   1. Ask your child why they think black paper is useful and if white paper would work as well. Why or why not? (Answer: The color black absorbs sunlight best, and therefore black paper absorbs the sun's heat. White paper would not work well because it would reflect a lot of sunlight instead of absorbing it.)
8. Cut two pieces of plastic wrap that are the same size as the top of the pizza box.
9. Use tape to secure the plastic wrap to the inside edges of the square window you cut into the box. You are creating an airtight window.
   1. Ask your child why they think it's important to create an airtight oven. (Answer: Your oven should be airtight in order to prevent any of the sun's heat from escaping it.)
10. Roll up some newspaper pages into tubes to stuff into the sides of the box. Make sure you are still able to close the lid of the pizza box.
    1. Ask your child what they think the purpose of the newspaper is. (Answer: Newspaper insulates the oven and prevents heat loss.)
11. Finally, it's time to test out your oven by cooking s'mores! Use a wooden skewer or ruler to prop open the flap at an angle, so that it reflects sunlight onto the food.

“Pizza Box Oven for S'mores" by Gerry Dincher / Cropped / CC BY-SA 2.0