MBL Lesson Plan: What Causes the Seasons? (Lab) Adapted from Vernier teacher resources

Aim: To examine how the solar radiation effects the Earth depending on it’s axis during different times of the year

Grade Level: Middle School Science

Objectives:

By the end of this lab students will be able to:

Materials

Lesson Overview

In this experiment, a simulated sun—a light bulb—will shine on a Temperature Probe attached to a globe. We will study how the tilt of the globe influences warming caused by the lighted bulb. If globes with adjustable tilt are used, make sure the tilt is 23.5 degrees. A fan may be used to cool the globe and probe between runs. If a 150-watt bulb is available, larger temperature changes can be obtained and longer data collection periods can be used.

Background

Because the axis of the earth is tilted, the earth receives different amounts of solar radiation at different times of the year. The amount of solar radiation received by the earth or another planet is called insolation. The tilt of the axis produces the seasons. The rays from the sun strike the earth more directly (closer to perpendicular) in the northern hemisphere than they do in the southern hemisphere. When the sun's rays strike more directly, they tend to warm up the earth more than when they strike at a sharp angle. Since the North Pole area receives light (and warmth) all day long, the North Polar Ice Cap will melt back during the summer. While the Northern Hemisphere is experiencing summer, the Southern Hemisphere is having a winter season. At this time the South Pole Area is without sun (and warmth) all day long, therefore, the ice around Antarctica builds up due to the lack of heat. By examining the movies carefully, it is possible to determine where on the earth there will be 24 hour "days" and 24 hour "nights". On the movie on the right, the Northern Hemisphere is receiving less direct solar rays (or none at all) while the Southern Hemisphere is receiving more direct solar radiation. By examining the movie carefully, it is possible to determine where on the earth there will be 24 hour "days" and 24 hour "nights". This will be the opposite to the situation observed in the movie on the left. Therefore, in the movie on the right, the Southern Hemisphere gets warmer (summer) and the Northern Hemisphere gets colder (winter). The tilt of the earth's axis creates a situation in which the directness of the sun's rays changes throughout the year as the earth orbits the sun. This change to the Angle of Insolation (the angle at which the sun's rays strike the earth) is what makes certain parts of the earth either warm up more or cool down - creating the seasons.

Procedure and Timing

20-minutes/ Beginning: Conducting the lab-Demo for Students

1. Ready the light bulb (simulated sun).

a. Fasten the lamp to a ring stand as shown in Figure 1.

b. Stand the ring stand and lamp in the center of the work area.

c. Position the globe with the North Pole tilted away from the lamp.

d. Position the bulb at the same height as the Tropic of Capricorn.

Note: The sun is directly over the Tropic of Capricorn on December 21, the first day of winter.

2. Attach the Temperature Probe to the globe. Figure 2

a. Find a city or location on the globe.

b. Tape the Temperature Probe to the globe with the tip of the probe at the location. Tape the probe parallel to the equator. Place the tape about 1 cm from the tip of the probe.

c. Fold a piece of paper and wedge it under the Temperature Probe to keep the tip of the

Temperature Probe in contact with the surface of the globe as shown in Figure 2.

3. Position the globe for winter (in the Northern Hemisphere) data collection.

a. Turn the globe to position the North Pole (still tilting away from the lamp), the location, and the bulb in a straight line.

b. Cut a piece of string 20-cm long.

c. Use the string to position the location on the globe 20 cm from the bulb.

d. Do not turn on the lamp until directed in Step 5.

4. Prepare the computer for data collection by opening the Experiment 10 folder of Middle School Science with Computers. Then open the experiment file that matches the probe being used.

5. Collect winter data.

a. Note and record the temperature displayed in the Meter window.

b. Click Collect to begin data collection.

c. After the first temperature reading has been taken, turn on the lamp.

d. When data collection stops after 5 minutes, turn the lamp off.

e. Choose Store Latest Run on the Data menu.

6. Position the globe for summer data collection.

a. Move the globe to the opposite side of the lamp.

b. Position the globe with the North Pole tilted toward the lamp. Note: This represents the position of the Northern Hemisphere on June 21, the first day of summer.

c. Turn the globe to position the North Pole, the location, and the bulb in a straight line.

d. Use the string to position the location on the globe 20 cm from the bulb.

e. Do not turn on the lamp until directed in Step 7.

7. Click Collect    summer data.

a. Let the globe and probe cool to the temperature that was recorded in Step 5.

b. Click Collect to begin data collection.

c. After the first temperature reading has been taken, turn on the lamp.

d. When data collection stops after 5 minutes, turn the lamp off.

e. Click the Statistics button , and then click OK  to display Statistics boxes for both runs.

Record the minimum and maximum temperature for each run.

8. Print copies of the graph

9. Record data and answer follow up questions in the data information

table student handout.

30 Minutes / Middle: Students perform the activity and fill in student handout

15 Minutes Ending/ Assessment

Summarize the activity by examining and discussing data chart and handout questions with students to access comprehension and clarify misconceptions.

Extension

Repeat the experiment for other locations in the Northern and Southern Hemispheres.

Name: ______________                                                              Date:_________

What Causes the Seasons?

 Data Collection Table

Processing the Data

1. In the space provided in the Data table, subtract to find the temperature change for each season.

2. How does the temperature change for summer compare to the temperature change for winter?

3. During which season is the sunlight more direct? Explain.

4. What would happen to the temperature changes if the earth were more tilted than 23.5 degrees?

5. As the globe is moved from its winter position to its summer position, the part of the globe closest to the bulb changes. Describe how it changes.

6. What other factors affect the weather in a region?