Plugging in to the Sun

Unit Summary

This hands-on construction project gets students cooking during a solar energy science unit. The class study begins by acting out the Earth's rotation around the sun to see how that causes shadows. Students conduct several investigations of the Earth's position and shadows with compass and thermometer measurements and observation. They research the dilemma of using fossil fuels and how solar energy might solve this problem. Students work as engineers, and their task is to build a solar cooker that can successfully cook an egg. If this works, it may be the basis for more exploration on using solar energy as an alternative to fossil fuels. Students display their learning in multimedia presentations or newsletters.

Curriculum-Framing Questions

• Essential Question
  What causes people (scientists) to consider new alternatives to solve problems?
• Unit Questions
  Why should solar energy be considered as an alternative to fossil fuels?
  How can you design a device that will transfer the sun’s energy for a useful purpose?
• Content Questions
  What are the factors that limit solar heat transfer? 
  What effect does solar energy have on different materials, and how can we make use of these effects?
  How is heat transferred? 
  How does the Earth’s rotation and the sun’s position affect heat and temperature on Earth?

Assessment Processes

View how a variety of student-centered assessments are used in the Plugging In to the Sun Unit Plan. These assessments help students and teachers set goals; monitor student progress; provide feedback; assess thinking, processes, performances, and products; and reflect on learning throughout the learning cycle.

Instructional Procedures

Prior to this unit:

• Review the terms and general concepts in the background information document
• Ensure students know how to use a compass and a thermometer
• Confirm that students have experience transferring math skills into a science context
• Verify that students know how to research and document information on the Internet
• Select student volunteers for sessions 7 through 9 (as described later in this unit plan)

Session 1
Begin by asking the students the Essential Question, What causes people (scientists) to consider new alternatives to solve problems? Students can brainstorm in groups and reflect on what causes scientists to develop new inventions and find alternatives. Ask students, What would happen if we always did things the ways they have always been done? Students also reflect back on this question at the end of the project.

Begin with a project introduction slideshow, and follow the presentation with a class discussion framed around the following questions:

• How can you design something that will transfer the sun’s energy for a useful purpose? 
• How does a conventional oven cook food? (Probe for and develop two ideas—oven cooking requires a heat source and an insulated box that holds heat. A temperature gauge is a helpful additional feature.)

Develop the ideas of solar cooking further by posing the following questions:

• Some say an egg can be fried on a sidewalk on a hot day. Is this true?
• Has anyone tried it?  
• How hot would it have to be to cook an egg?

As a class demonstration, cook an egg in a small custard cup in a standard preheated 350ºF toaster oven. Rest a meat thermometer in the egg and determine the internal temperature. While it's cooking, discuss whether radiant heat (heat transferring through space), conduction heat(heat transferring from direct contact with heat source), or convection heat (heat transferring though moving, heated air) is cooking the egg. When the egg is deemed cooked, read the thermometer. (Note: An egg is cooked when its internal temperature reaches 160ºF. Do not measure oven temperature.)

Introduce the following challenge: Students work as engineers, and their task is to build a solar cooker that can successfully cook an egg. If the cookers work, it may be the basis for more exploration on using solar energy as an alternative to fossil fuels. Tell students that they must develop a rationale for the use of solar energy based on research and address the question, Why should solar energy be considered as an alternative to fossil fuels?

Sessions 2 and 3
Have students meet in groups to determine the features they think their solar cooker will need to meet the challenge.

Reconvene and teach about reflection and absorption of the sun's rays. Discuss the reasons why an egg most likely cannot be cooked on a sidewalk, and have students further refine the necessary features of solar cookers. Discuss answers to the question, What effect does solar energy have on different materials, and how can we make use of these effects?

Next, using the students’ criteria and a set of print and electronic resources you provide, instruct students to begin evaluating a variety of solar cooker designs. Circulate around the room as groups work, taking anecdotal notes.

During the last 10 minutes, have students respond in their science journals to Questions 1 and 2 on the probing understanding sheet. Review the journals and provide further instruction as necessary.

Session 4
Instruct groups to choose a preliminary solar cooker design from their Internet research. Tell them to be prepared to defend their choice.

Using Question 3 from the probing understanding sheet, have each group develops a short paper describing how the design of their oven relates to its function. This could be framed as a defense of the design they chose as compared to an oven design they rejected.

Session 5
Have students read their papers to the class, and, informed by the discussion, make their final design selection.

Prior to constructing the designs, have students sketch their designs in journals, labeling each feature and describing its function.

Session 6
Develop the concepts of heat transfer relating to radiant, convection, and conduction heat. Tell students to use this information when choosing the method of cooking they want to use (baking, broiling, boiling, or frying; in shell or out of shell).

Have each group assign tasks within their group and begin collecting materials. Pose Question 4 from the probing understanding sheet. Again, review the journals and modify instruction as necessary.

Sessions 7 through 9
Provide ample time for students to construct their cookers.

During these days, have students investigate the effects of the Earth’s rotation and the sun’s position on heat and temperature on Earth by completing the finding north activity, using the shadow plot procedures.

Have students respond to Question 5 from the probing understanding sheet.
 
Session 10
Spend one period troubleshooting cookers and measuring interior temperatures. Students should create a chart or graph of temperatures and corresponding times. The temperatures can be compared to a temperature guide for foods found in their research.

Using Question 6 from the probing understanding sheet, ask students to interpret a solar cooker graph. Later, their data can be graphed using spreadsheet software. This activity, along with the shadow plot procedures, helps students fine-tune the function of their oven, and choose the time and position for cooking.

Conference with students to help answer any questions they have and to probe for understanding of the concepts they have encountered any difficulty with.
 
Session 11 (or the next sunny day)
Cook-Off! Students use their solar cookers to cook eggs.

Take lots of conventional, digital, and video images! Safety precaution: If eggs are eaten, make sure they have been cooked to at least 160ºF and are consumed immediately after cooking.

Sessions 12 through 14
Explain that students will now share their learning in a project.

In small groups or pairs, have students develop a slideshow presentation, brochure or newsletter.

Distribute the project checklist to help students keep track of their progress. Inform students that all projects should include:  

• Rationale for design choice and reasons why a person would want to use solar energy over fossil fuels 
• One or more digital photos of the cooker, preferably in stages of development
• Graph showing oven temperature over time plus a caption interpreting the graph
• Discussion of the process and results (introduction, process, troubleshooting, challenge results, and final thoughts)
• Citation for cooker design and other information

Provide the solar rubric and review with students to help ensure they understand the assessment criteria before they start to work.

Session 15
Conduct a class discussion on the Essential Question, What causes people (scientists) to consider new alternatives to solve problems?  Students should be more enlightened on the factors that cause scientists to explore new solutions to problems.

Ask students to write responses to Questions 7 through 9 on the probing understanding sheet.

Prerequisite Skills

• Experience using a compass to orient objects on Earth
• Familiarity using a thermometer to monitor temperature change in a variety of materials
• Skill in applying mathematics in the context of science 
• Basic keyboarding and computer navigation skills (including opening and saving documents, launching programs, documenting research, and finding information on the Internet)

Differentiated Instruction

Much of this work can be done at a variety of academic levels. As needed, partner students for computer work with technically skilled students.

Special Needs Student

• Team the student with stronger readers 
• Allow the student to dictate journal entries or test answers 
• Narrow assignments to the most important features 
• Allow the student to make selection from multiple choice answers or respond orally rather than production and essay responses on probing understanding questions 
• Ask support personnel for assistance 
• Provide a daily outline of tasks to aid organization and work completion

Gifted/Talented Student 

• Provide opportunities for extended activities, such as constructing a more complex parabolic cooker, studying atomic fusion as it relates the sun's energy, or studying how microwaves agitate molecules to heat food 
• Present the problem of storing solar energy and have students investigate solutions

Nonnative Speaker 

• Provide visual models when possible 
• Ask for translation help from more proficient bilingual students 
• Ask ELL support personnel to develop a two-language glossary of terms to aid vocabulary development 
• Allow written work to be completed in the student’s native language for later translation

Credits

Marge Stembel of Garrett Park, Maryland participated in the Intel® Teach Program, which resulted in this idea for a classroom project. A team of teachers expanded the plan into the example you see here.