Lesson: Light and Heat

Prerequisites:

• Thermometer Reading
• Day and Night (optional)
• Direct and Diffuse (optional)

Objectives:

1. Create a link between light, energy, and heat
2. An important concept for future lessons

Materials:

• 5 magnifying glasses as large as possible (~5 inch diameter)
• tissue paper
• 3 glasses
• room temperature water
• 3 thermometers
• sunny window or grow light
• blue food coloring

Introduction:

Body:

1. Fill 3 glasses with 1/2 cup of room temperature water. Place 5 drops of dark food coloring in each glass. During the middle part of a sunny day, take the class outside with the glasses and explain to the students that they are going to conduct an experiment to try to find the warmest and coldest locations on the school grounds. Ask for 3 student volunteers. The first student needs to place one glass in the sunniest location he/she can find. The second student places his/her glass in a part sun/part shade location such as in the shade of a tree. The third student places his/her glass in a shady spot such as next to a building. Leave the glasses in the spots for about an hour. Meanwhile, have the students fill in and color the prediction page of their weather journal and begin work on experiment number 2.

2. Remain outside and divide into groups of 5-6 students. (Note: teacher should model the following experiment before students are sent off on their own.) Begin by holding up a sheet of tissue paper and asking: "Do you think the sun can burn this paper?" Have the students gather around the teacher in a circle and explain how you can use a magnifying glass to concentrate the sunlight into a small area. Demonstrate how this can be done using the tissue paper (it should smoulder and possibly ignite if the experiment is done correctly). Emphasize to the students that one needs to be patient and to hold the magnifying glass at a distance so only a small dot of light is concentrated on the tissue paper. It may be helpful to put an "X" on the tissue paper where the light should be focused. If the magnifying glass is held too close or too far away from the paper the light will not be focused and the heat will not be concentrated. (Caution: students should not concentrate the light on any part of themselves or others.) Discuss with the entire class what they observed. (You want them to hit on the idea that light is heat.)

3. Returning to the 3 glasses around the school grounds, ask each student to get a pencil and their weather journal. In small groups or individually have the students travel to each glass to read and record the temperatures on the thermometers placed in the 3 glasses. The temperatures should be recorded in the weather journal on the observation page.

Conclusion:

Vocabulary Words:

Evaluation:

1. Discussion:
   • "What did the magnifying glass and the hottest glass of water have in common?"
   • "What was the source of the heat for the two?" (Work toward a conclusion that sunlight warms things.)

2. Imagination:

   Some animals make their own heat in their body to stay warm like we do. Some animals are not able to do this. They need to find other ways to warm and cool themselves. Snakes, alligators, and turtles are all these kinds of animals. They are called "cold-blooded" animals. Pretend that you are a snake and you feel yourself getting too cold. What could you do to get warmer? Now pretend you are getting too warm. What could you do to cool yourself off?

Followup Lessons:

• The Seasons

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