Gr 7 Composition & Structure of Atmosphere Notes PDF

 **Candidate Name:** --------------------- --------------------------------------------------------- -- **Composition and Structure of the Atmosphere - Notes** **Sub: SST**...

 **Candidate Name:** --------------------- --------------------------------------------------------- -- **Composition and Structure of the Atmosphere - Notes** **Sub: SST** **Definition of Earth\'s Atmosphere** The Earth\'s atmosphere is a layer of gases surrounding the planet, held in place by gravity. It extends from the Earth\'s surface to about 10,000 kilometers (6,200 miles) into space. This atmosphere is crucial for supporting life by providing the air we breathe and protecting us from harmful solar radiation. Features and Importance of the Atmosphere Protective Shield: The atmosphere protects living organisms from harmful UV radiation and meteoroids. Climate Regulation: It helps regulate temperatures, maintaining conditions suitable for life. Weather Formation: The atmosphere is essential for weather patterns and the water cycle, influencing precipitation and temperature. Breathable Air: Provides the oxygen necessary for the survival of most living organisms. **Composition of the Atmosphere:** The atmosphere is made up of a mixture of gases, primarily: Nitrogen (N₂): 78%. Oxygen (O₂): 21%. Argon (Ar): 0.93% Carbon Dioxide (CO₂): 0.04% (increasing due to human activity) Trace Gases: Includes neon, helium, methane, and others in very small amounts. **Definition and Importance of Nitrogen and Oxygen**.Nitrogen (N₂):Definition: A colorless, odorless gas that makes up about 78% of the atmosphere. Importance: Essential for the growth of plants as it is a key component of amino acids and proteins. It also helps dilute oxygen, preventing rapid combustion and supporting stable environments. Oxygen (O₂): Definition: A colorless gas that constitutes about 21% of the atmosphere. Importance: Vital for the respiration of most living organisms. It is also crucial for combustion, allowing fire and energy production. **Structure of the Atmosphere** The atmosphere is divided into several layers, each with distinct features and importance: 1**. Troposphere:** Altitude: Extends from the Earth\'s surface to about 8-15 kilometers (5-9 miles). Features: Contains most of the atmosphere\'s mass and weather phenomena (clouds, rain). Importance: Where we live and breathe, crucial for life; temperature decreases with altitude. **2. Stratosphere:** Altitude: Extends from the troposphere to about 50 kilometers (31 miles). Features: Contains the ozone layer, which absorbs and scatters UV radiation. Importance: Protects living organisms from harmful radiation and helps stabilize temperatures. **3. Mesosphere:** Altitude: Extends from the stratosphere to about 85 kilometers (53 miles). Features: Temperatures decrease with altitude; meteors burn up in this layer. Importance: Protects the Earth\'s surface from meteoroids. **4. Thermosphere**: Altitude: Extends from the mesosphere to about 600 kilometers (373 miles). Features: Very high temperatures due to solar activity; contains the ionosphere, important for radio communication. Importance: Reflects radio waves back to Earth, aiding communication and navigation. **5. Exosphere:** Altitude: Extends from the thermosphere to about 10,000 kilometers (6,200 miles). Features: Extremely thin air; where atmospheric particles can escape into space. Importance: Represents the boundary between the Earth\'s atmosphere and outer space. *Summary* *The Earth\'s atmosphere is a vital layer of gases that supports life by providing air and regulating climate. Its composition includes essential gases like nitrogen and oxygen, each playing a crucial role in sustaining life. The atmosphere\'s structure, comprising various layers, serves important functions in protecting and maintaining the Earth\'s environment.*