Teacher Background
The air surrounding Earth is known as the atmosphere. Gas molecules in the atmosphere are held relatively close to Earth’s surface by gravity. The atmosphere is mostly nitrogen (78%) and oxygen (20%). The amount of water vapor in the atmosphere varies, but can be as much as 5% by volume. Other gases, present in much smaller amounts, also are extremely important parts of the atmosphere. Carbon dioxide (CO2), methane (CH4), and other gases, including water vapor, help radiate heat back toward Earth’s surface, thus keeping it much warmer than it would be otherwise. Ozone, which is present in tiny amounts in part of the atmosphere, filters out most of the harmful ultraviolet radiation from the sun.
Life on Earth would not be possible without the atmosphere, which protects the planet’s surface from extremes of temperature and harmful radiation and also provides essential water, carbon dioxide, oxygen, and nitrogen. This activity helps students learn about Earth’s atmosphere by creating a scale model.
Procedure and Extensions
Time
One or two 30-minute sessions
-
Ask students if they ever have seen pictures of astronauts in space. Ask, Why do the astronauts wear special suits? Mention that the space suits keep astronauts warm, provide them with air to breathe, and protect them from harmful rays from the sun. Follow by asking if we need to wear space suits on Earth. Help students recognize that the thin layer of gases surrounding Earth, the atmosphere, provides protection for all of the planet, as space suits protect the astronauts.
-
Mention that, as a class, the students will create a scale model of Earth’s protective layer of gases. Lay a sheet of brown or white paper (at least 2.5 m long) on the floor where students can work on it. Discuss the scale of the model with students (1 cm = 1/2 km; 2 cm = 1 km).
-
Distribute the Job cards to student groups. Each group will create and decorate a different part of the atmosphere model. Older students should measure and draw their own lines on the model. To facilitate work in groups, you may want students to cut off their sections of the model to complete in separate locations. (Groups 1 and 2 work on the same section.) Once completed, the sections can be taped together.
Group 1: Planet Earth. Have students draw a vertical line about 15 cm from the bottom of the sheet of paper (this line represents Earth’s surface) and create figures (mountains, forests, cities, etc.) using construction paper or other materials and adds them to the model. Remind students that the figures they create should be no more than 5 cm tall.
Group 2: First layer of the atmosphere (troposphere). Have students draw a line about 22 cm from the line designating Earth’s surface (this line represents the upper limit of the first layer), then add figures of weather phenomena (clouds, rain, lightning, etc.), as well as low-flying aircraft and hot air balloons. Point out to students that much of the pollution produced by burning wood and fossil fuels remains in the troposphere. The gases responsible for keeping Earth warm (greenhouse gases) are found in this layer. Temperatures within the troposphere decrease with altitude.
Group 3: Second layer of the atmosphere (stratosphere). Have students draw a line about 100 cm from the line for Earth’s surface (this line represents the upper limit of the second layer), then add figures of storm clouds, jet aircraft, wind, and a representation of the protection provided by ozone molecules in this layer. The stratosphere is warmer due to absorption of UV light by ozone.
Group 4: Third layer of the atmosphere (mesosphere). Have students draw a line about 170 cm from the line for Earth’s surface (this line represents the upper limit of the third layer), then add figures of feathery ice clouds and weather balloons. The mesosphere is very cold.
Group 5: Fourth layer of the atmosphere (thermosphere). Have students add figures of spacecraft, satellites, and meteors (shooting stars) to the model. If students were to draw a line, the upper limit of the thermosphere would be 1,200 cm (12 m) from the baseline of the model. This group may use the remainder of the space on the sheet. This layer is very hot in some parts—up to 1,700°C or more—due to absorption of radiation by different atoms and molecules.
Group 6: Space outside Earth. Have students create figures representing other components of the solar system and universe and place them around the room. The exosphere contains very small amounts of hydrogen and helium, and continues until it merges with space.
-
Have each group label its layer on the model. Display the model somewhere in the classroom. Encourage students to note that most activities involving the atmosphere occur very close to Earth’s surface. Leave the model available for students to refer to throughout the unit.
