Active+Learning

How to make a solar oven


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 * Overview **


 * Title:** Solar Ovens


 * Age:** This lesson is designed for middle school students, but could be easily altered for elementary or high school students.


 * Time Frame:** This lesson takes between two and three class periods. One day to give an overview of the concepts of heat transfer (endothermic), solar radiation. Another day to construct the solar ovens. And finally, a day to test the ovens and analyze the results.


 * Overview:** Students will apply the concept of heat transfer and solar energy as they work to create their own solar ovens. We will begin by defining applicable terms. Students will then analyze how these terms relate to a model solar oven. Following this, they will work in groups to create their own ovens. As they create their ovens, they must rationalize the choices they make. After the ovens have been created and tested the class will compare data and analyze what worked well and what didn't. Finally, students will answer a series of questions in order to assess their understanding of solar ovens, their function, and applied concepts.

**Rationale** Students will be studying heat as a form of energy in order to better understand the transfer of energy. This will be done using reflection and heat transfer to create thermal energy. This activity, using household materials, will help students see examples of how exothermic and endothermic reactions are caused using solar radiation, as well as fulfilling Washington State science requirements.

__Learning Targets__  __Related Washington State Science Standards: Science EALR 2005__ 1.3. Changes: Understand how interactions within and among systems cause changes in matter and energy.
 * 1) Students will be able to work cooperatively in groups to create a solar oven.
 * 2) Students will be able to test their solution to determine whether or not it will solve the problem.
 * 3) Students will be able to use their results in order to modify the design.
 * 4) Students will be able to use their results to discuss the transfer of head
 * 5) Students will identify the specific requirement for making a solar oven
 * 6) Students will evaluate the effectiveness of altering the design of their oven to create different results.

__Science EALRs 2009__ 6-8 PS3A-Energy exists in many forms: heat, light, chemical, electrical, motion of objects, and sound. Energy can be transformed from one form to another and transferred from one place to another.

6-8 PS3B - Heat (thermal energy) flows from warmer to cooler objects until both reach the same temperature. Conduction, radiation, and convection, or mechanical mixing, are the means of heat transfer.

6-8 PS3C - Heat (thermal energy) consists of random motion and the vibrations of atoms and molecules. The higher the temperature, the greater the atomic or molecular motion. Thermal insulators are materials that resist the flow of heat.


 * Description **

Procedure We will construct a model solar oven ahead of time (see construction) so that we can use this as an example while analyzing how specific terms relate to the function of a solar oven.

On the first day we will give brief introduction to three different terms. 1) Heat transfer 2) Endothermic vs. Exothermic and 3) Solar Radiation. After defining and explaining each term, we will bring out a sample solar oven and hand out a list of directions on how it was created (see construction). In groups of five, students will discuss how each of these terms are applied in the function of a solar oven.

Given this background information on solar oven construction as well as the applicable terms, students will create their own solar oven. Each oven must have two traits that are different than the example oven. Each of these traits must be accompanied by a written explanation as to why this adaptation will allow their oven to work better. Each explanation must contain one of the three terms (heat transfer, endothermic vs exothermic, or solar radiation).

After the ovens are complete, we will discuss a way to measure their effectiveness and the class will come to a consensus on how measurements will be calculated. Some ideas are: Heat a cup of water then take the temperature of that water, or how long it takes to melt an ice cube that is a specific size.

Lets assume that students chose melting an ice cube as their means of measurement. Students will take their ovens outside, chose a location, and arrange their oven so it is reflecting light in the manner that they want. Then the teacher will say ready, set....go and all groups will place their ice cube inside their oven. An additional oven will be placed in direct sunlight, but not in an oven in order to serve as a control. Each group will be equipped with a stop watch in order to time how long it takes for their ice cube to melt.

Cardboard pizza box Exacto knife or scissors Aluminum foil Plastic wrap Black construction paper Stick or dowl Newspaper
 * Materials**

**Construction**
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 * 1) **Cut a large flap in the lid of the pizza box. Cut along three sides, leaving about an inch between the sides of the flap and the edges of the lid. Fold this flap out so that it stands up when the box lid is closed. Cover the inner side of the flap with aluminum foil so that the rays from the sun will be reflected off.**
 * 2) **Use clear plastic wrap to create an airtight window for sunlight to enter into the box. Do this by opening the box and taping a double layer of plastic wrap over the opening you made when you cut the flap in the lid. Leave about an inch of plastic overlap around the sides and tape each side down securely, sealing out air.**
 * 3) **Line the bottom of the box with aluminum foil to reflect heat and then cover that with black construction paper--black absorbs heat.**
 * 4) **Now your oven is ready to try out! Take it outside to a sunny spot and adjust the flap until the most sunlight possible is reflecting off the aluminum foil and onto the plastic-covered window. Use a stick or a dowel to prop the flap at the right angle.**
 * 5) **Your solar oven will reach about 200 degrees on a sunny day, and will take longer to heat things than a conventional oven. Try melting mozzarella cheese over toast with basil and tomatoes, warming leftovers for lunch, or experimenting with any other food you can think of ideas for ** **. **


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**Assessment**

Students will be assessed in several ways.


 * 1) Students will be assessed on whether or not their solar oven meets the minimum requirements of the assignment.
 * 2) Students will be able to formulate a hypothesis as to how their specific design will change the effectiveness of their oven.
 * 3) Will be able to use key terminology to describe how their solar oven functions.
 * 4) After the construction and melting activity, students will complete a written assignment where they will be asked questions regarding the role of each specific material used in the oven (saran wrap, foil, newspaper, black paper). This will include the reaction difference if each material was treated as a variable. The students will use this information to consider how they might improve their design.

Q: Can anyone tell me what we have been studying this quarter in Science? Q: Can someone name a type of energy for me? Q: What type of energy does the sun give us? Q: Can someone tell me why we want light? Q: What are different ways we can cook food? Q: What do you think the aluminum foil is for? Q: What do you think the saran wrap is for? Q: What do you think the rolls of newspaper are for? Q: What do you think the black paper is for?