Absorption and Reflection of Solar Energy

Category:Learning Cycle

Learning Objectives:

1. The student will observe and explain absorption and reflection.
2. The student will compare energy conversions of cities with the country
3. The student will complete and interpret a graph of scientific data.

Materials, equipment and/or facilities:
You will need the following for each group of students performing the lab:

• Four laboratory thermometers
• white construction paper
• black construction paper
• aluminum foil
• four plastic cups
• graph paper
• colored pencils

Sequence and duration of each part of lesson:
Time: about 40 minutes

Exploration: Organize the students in pairs

Student Procedure:

Each pair of students should:

1. Cover each cup with a different material-white paper, black construction paper, aluminum foil, and one with no covering.
2. Fill each plastic cup two-thirds full of water.
3. Place a thermometer in each cup.
4. Place all four containers in sunlight for thirty minutes.
5. Take temperature readings initially and every five minutes. Write down data on your data table.
6. Plot each container's data on the same graph (temperature vs. time) in a different color.

Concept Invention:
Looking at your graph write answers to the following questions.

1. What are the temperature readings for each of the containers when you started? How do they compare?
2. What are the temperature readings for each container at the end of the time? How do they compare?
3. What happened to the sunlight?
4. What evidence do you have that sunlight was reflected or absorbed?
5. If all of the cups received the same amount of sunlight then how can you explain why they have different temperatures?

In a discussion ask students to apply their knowledge about how the various materials reflect and absorb sunlight in every day situations.
For example: white clothing in Africa, colors of cars, mirrored windows, silver backed light fixtures, etc.

Applications:
Knowing what you know about energy conversions:

1. Why is it usually cooler in the country than it is in the city?
2. If plants absorb sunlight why isn't there as much heat produced?
3. If the Law of Conservation of Energy states that energy cannot be created or destroyed then what energy conversion is taking place in plants to use up that extra energy?