Exploring Radiation: Solar S'mores

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Objective

SWBAT apply the process of radiation to creating a solar oven and cooking food.

Big Idea

Students love to cook and to eat. What better way to teach about solar heat than to make a solar oven and cook S'mores?!

Engage

10 minutes

I start the lesson by displaying a sample solar oven on a table in front of the class.

I have the students gather around to look at it closely. I ask the students, “Can anyone tell me what they think this contraption might be? (Answers vary)

I ask them to think about what we learned in the prior lesson when we made popcorn. (types of heat transfer)

I tell the students that this item is a solar oven I made in my kitchen. I explain that today we are each going to use the Sun’s light energy to make an oven. The oven converts the sun’s light energy into heat energy for cooking. I ask the students to think about what they learned yesterday and to recall which type of heat transfer comes from the sun’s rays. (radiation)  

I have the students examine the solar oven carefully, listing all the materials I used to create it, then I ask the following questions:   

  • What do you think the aluminum foil is for? (To gather more light.  Light bounces off of the foil into the oven.  A mirror could work as well.)
  • What do you think the plastic wrap is for? (Insulation so heat can’t escape – similar to a blanket.  It has to be transparent so light can get through.)
  • What do you think the black paper is for? (Absorbs the light.  Compare this to wearing a white shirt or a black shirt on a summer day.)

After we know the purpose of each item in the box, I explain that we want to create as much heat as possible in order to use this as an oven. At this point, a lot of the kids will want to know what we are cooking… to which I reply, “S’mores!”

Explore

30 minutes

I have the students form groups of 3-4 and hand out the following materials to each group:

  • 1 pizza box
  • 1 sheet of black construction paper
  • 2 sheets of tin foil*
  • 2 sheets of Saran or plastic wrap*
  • scissors          
  • scotch tape
  • glue stick
  • marker
  • wooden stick or dowel
  • 1 copy of the Solar Oven Directions for each student

*be careful to leave the foil and plastic wrap flat and in good condition

Students create their solar ovens as a group, and place them in a spot outside where they feel they will produce the most heat. I DO NOT provide guidance with this part. I want them to form their own hypotheses as to where would make the most sense to place their oven.

If they fail at producing enough heat, it’s not a problem. (This food does not need to be cooked in order to be eaten.) We leave the ovens in the sun for at least 30-40 minutes, in order to allow them to “preheat”.  Students can use thermometers to take the temperature of their ovens every 10-15 minutes and log that information. It is a great way to collect and analyze data in an authentic situation.

Explain

10 minutes

Once the ovens have had time to preheat, we bring out the graham crackers and marshmallows. In order for them to soften up enough to get gooey, each student cooks a marshmallow on top of a single graham cracker for another 30-60 minutes. Once the marshmallows are soft, we add the chocolate and top with another graham cracker. At this time, we close the lids and remove them from the heat. This ensures that the ovens stay warm enough to soften the chocolate, but not too hot to melt it completely, leaving us with a soupy mess. This process usually takes 10-15 minutes. 

As they cook, we observe the changes they are making, and I ask questions, such as:

  1. Where does the heat come from to cook the s’mores?
  2. Can you tell if the oven is getting hotter by looking at the s’more?
  3. What chemical processes are occurring in the graham cracker? The marshmallow? The chocolate?

Elaborate

15 minutes

While students are waiting for their S'mores to cook, I pass out the Solar Cooking article for them to read. As they read I have them highlight key information from the article. After reading, I have the students draw a diagram of how solar ovens use radiation to cook their foods, including drawings, labels, and captions to describe the process. This will serve as a way for me to assess their understanding of the processes involved in heat transfer and cooking our S'mores.

Evaluate

10 minutes

By this point, the S'[mores are usually ready to eat! Working carefully, as the ovens may be hot, I have the students gather their ovens and bring them inside to cool. Once they are cool enough to touch, the students may remove and eat their S'mores.

While they are eating,  I pair everyone up and have them share their diagrams with their partner, describing the process of cooking with the Sun's rays as if their partner had no knowledge of the concepts whatsoever. After sharing, it is the job of each partner to ask clarifying questions and to provide feedback to revise the diagrams, if necessary. Through the quality of both the diagram and the discussion, I am able to determine the level of understanding on the part of each student.

Check out their Solar S'mores!