Unit 3 Lesson 2 The Atmosphere Copyright © Houghton Mifflin Harcourt Publishing Company 1

Unit 3 Lesson 2 The Atmosphere Florida Benchmark SC.6.E.7.9 Describe how the composition and structure of the atmosphere protects life and insulates the planet. Copyright © Houghton Mifflin Harcourt Publishing Company 2

Up and Away! What is Earth’s atmosphere? Unit 3 Lesson 2 The Atmosphere Up and Away! What is Earth’s atmosphere? The atmosphere is the mixture of gases that surrounds Earth. The functions of the atmosphere include protection from the sun, maintaining temperature, and supplying gases necessary for breathing. Copyright © Houghton Mifflin Harcourt Publishing Company 3

What is Earth’s atmosphere? Unit 3 Lesson 2 The Atmosphere What is Earth’s atmosphere? The atmosphere is made of 78 percent nitrogen gas, 21 percent oxygen gas, and 1 percent other gases. The atmosphere also contains small particles of dust, volcanic ash, sea salt, smoke, skin, bacteria, and pollen. Copyright © Houghton Mifflin Harcourt Publishing Company 4

What is Earth’s atmosphere? Unit 3 Lesson 2 The Atmosphere What is Earth’s atmosphere? In the atmosphere, water is found in the clouds as liquid droplets and solid water in the form of snow and ice crystals. Most water in the air is in the form of water vapor. Water vapor is an invisible gas. Copyright © Houghton Mifflin Harcourt Publishing Company 5

How do pressure and temperature change in the atmosphere? Unit 3 Lesson 2 The Atmosphere How do pressure and temperature change in the atmosphere? Gravity pulls gas molecules in the atmosphere toward Earth, causing pressure. Air pressure is the measure of the force with which air molecules push on a surface. Copyright © Houghton Mifflin Harcourt Publishing Company 6

How do pressure and temperature change in the atmosphere? Unit 3 Lesson 2 The Atmosphere How do pressure and temperature change in the atmosphere? As altitude, or distance from Earth’s surface, increases, air pressure decreases. As altitude increases, temperatures change. Some parts of the atmosphere are warmer because of gases that absorb solar energy. Copyright © Houghton Mifflin Harcourt Publishing Company 7

Look Way Up What are the layers of the atmosphere? Unit 3 Lesson 2 The Atmosphere Look Way Up What are the layers of the atmosphere? The atmosphere is divided into four layers based on temperature and other properties. The thermosphere is the uppermost layer with temperatures that increase as altitude increases. The thermosphere feels cold because particles are so far apart. Copyright © Houghton Mifflin Harcourt Publishing Company 8

What are the layers of the atmosphere? Unit 3 Lesson 2 The Atmosphere What are the layers of the atmosphere? The mesosphere is between the thermosphere and stratosphere. Temperatures decrease as altitude increases. Meteoroids begin to burn up in the mesosphere. Copyright © Houghton Mifflin Harcourt Publishing Company 9

What are the layers of the atmosphere? Unit 3 Lesson 2 The Atmosphere What are the layers of the atmosphere? The stratosphere is between the mesosphere and troposphere. Temperatures generally increase as altitude increases. Ozone in the stratosphere absorbs ultraviolet radiation from the sun, which warms the air. Copyright © Houghton Mifflin Harcourt Publishing Company 10

What are the layers of the atmosphere? Unit 3 Lesson 2 The Atmosphere What are the layers of the atmosphere? The troposphere is the lowest layer of the atmosphere. Temperature generally decreases as altitude increases. Temperatures near the surface vary greatly. The troposphere contains 80 percent of the atmosphere’s total mass. Copyright © Houghton Mifflin Harcourt Publishing Company 11

What are the layers of the atmosphere? Unit 3 Lesson 2 The Atmosphere What are the layers of the atmosphere? How do temperatures differ with altitude in the atmosphere? Copyright © Houghton Mifflin Harcourt Publishing Company 12

Here Comes the Sun … How does the atmosphere protect life on Earth? Unit 3 Lesson 2 The Atmosphere Here Comes the Sun … How does the atmosphere protect life on Earth? Earth’s atmosphere reflects or absorbs most of the radiation from the sun. The ozone layer is in the stratosphere and contains a high concentration of ozone. It absorbs most of the solar radiation. Copyright © Houghton Mifflin Harcourt Publishing Company 13

How does the atmosphere protect life on Earth? Unit 3 Lesson 2 The Atmosphere How does the atmosphere protect life on Earth? Ozone-layer thickness changes by season and location. Scientists have discovered a steady decrease in the overall volume of ozone over time. Ozone can also be destroyed by certain chemicals in the air. Copyright © Houghton Mifflin Harcourt Publishing Company 14

How does the atmosphere protect life on Earth? Unit 3 Lesson 2 The Atmosphere How does the atmosphere protect life on Earth? The greenhouse effect is the process by which gases in the atmosphere absorb and radiate energy as heat back to Earth. Shortwave radiation from the sun reaches Earth’s surface and reradiates back into the atmosphere, where it is trapped by greenhouse gases. Copyright © Houghton Mifflin Harcourt Publishing Company 15

How does the atmosphere protect life on Earth? Unit 3 Lesson 2 The Atmosphere How does the atmosphere protect life on Earth? How is the heat inside of a closed car in the summer similar to the greenhouse effect? Copyright © Houghton Mifflin Harcourt Publishing Company 16