- Definition and forms of energy
- Energy from the sun
- Electromagnetic spectrum
- Radiation, conduction, and convection
- Define energy.
- Describe solar energy.
- State how heat moves through the atmosphere.
- Describe how solar energy varies across Earth’s surface.
- Explain the greenhouse effect.
electromagnetic spectrum: total range of wavelengths of energy given off by the sun
energy: ability to do work
greenhouse effect: warming of Earth by gases in the atmosphere that absorb energy
greenhouse gas: gas such as carbon dioxide that absorbs energy in the atmosphere and keeps Earth warm
infrared light: light with wavelengths longer than those of visible light that humans can feel as heat
photon: tiny packet of energy given off by the sun that travels in an electromagnetic wave
ultraviolet (UV) light: light with wavelengths shorter than those of visible light that harms living things
visible light: range of wavelengths of light that humans can see
Introducing the Lesson
If the day is sunny, you can use a simple demonstration to introduce solar radiation and the electromagnetic spectrum. Do demonstration #25 (“Track Star”) at the following URL. You will place a sheet of paper on the ground beside a drinking glass half-filled with water and held in full sunlight. Explain to the class that the glass of water acts as a prism and breaks the sunlight into the different wavelengths (colors) of visible light. Tell students they will learn more about sunlight, its range of wavelengths, and how its energy affects the atmosphere when they read this lesson.
Conduction is one of the ways that energy is transferred through Earth's atmosphere. Illustrate the process of conduction with the creative demonstration at the following URL. After watching the demonstration, students should be able to provide a molecular explanation of conduction and explain why different materials conduct heat at different rates. They will also be able to identify air as a poor heat conductor (an insulator).
Building Science Skills
This lesson describes how the greenhouse effect helps to moderate Earth’s temperature. In the activity at the URL below, students will build simple models to investigate how a greenhouse retains heat. After the activity, discuss with the class how Earth’s atmosphere is like a greenhouse and how the atmospheric greenhouse effect retains heat.
Work with students to make a table comparing and contrasting the three methods of heat transfer (conduction, convection, and radiation). Suggest that they add sketches to the table to illustrate each method of heat transfer.
Challenge a small group of students to model the way the tilt of Earth on its axis affects the angle at which solar radiation strikes Earth’s surface and the degree to which the energy is concentrated or spread out over the surface. They could use a Styrofoam ball with a skewer pushed through its center to model Earth and its axis, and they could use a flashlight to model the sun. After the demonstration, conduct a class discussion relating the demonstration to Earth’s seasons.
Students will develop an understanding of how heat is transferred by radiation with the inquiry activity at the URL below. Specifically, students will observe how the physical characteristics of a surface affect the way the surface absorbs and releases heat from the sun. They will also understand that radiation of heat occurs without the involvement of a physical object. Then they will apply what they learn from the activity to interpret real-world situations involving solar radiation. The activity includes background information and assessments.
Most people believe incorrectly that the atmosphere is heated directly by sunlight. They do not understand the contributions of the three heat transfer mechanisms—conduction, convection, and radiation—to warming the atmosphere. Therefore, they do not appreciate that the atmosphere is heated from the ground up, even though the original energy comes from the sun. Discuss and correct the misconceptions with your students.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 15.2 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
Energy from the sun heats the air in Earth’s atmosphere. You might predict that air temperature would increase steadily with altitude. After all, the higher you go, the closer you are to the sun. But it’s not that simple. Besides the sun, what might heat up the atmosphere?
How do you think air temperature might change with altitude?