Elementary schoolers discover how engineers use solar energy to heat buildings. They take a close look at some of the materials used: sand, salt, water, and shredded paper and evaluate the efficiency of each material. An incredible lesson plan that has learners divide up into groups. Each group is assigned one of the materials, and they perform experiments to determine the solar index of each. Terrific worksheets and websites are embedded in the plan to support the teaching and learning. A top-notch science lesson plan!