🌍 Class 7 Geography – Chapter 4
Air
NCERT Notes | Easy Explanation

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🌬️ Introduction

Air is an important natural resource. All living beings need air to survive. Air surrounds the Earth and forms the atmosphere.

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🫁 Composition of Air

Air is a mixture of many gases.

• Nitrogen – 78%
• Oxygen – 21%
• Carbon dioxide – very small amount
• Other gases – Argon, Neon, etc.

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🌱 Importance of Gases

• Oxygen – needed for breathing
• Carbon dioxide – used by plants for photosynthesis
• Nitrogen – helps in plant growth

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🌫️ Atmosphere

The atmosphere is a thick blanket of air that surrounds the Earth. It protects us from harmful rays of the Sun.

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🏔️ Structure of the Atmosphere

• Troposphere – weather changes occur here
• Stratosphere – contains ozone layer
• Mesosphere
• Thermosphere
• Exosphere

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☀️ Weather and Climate

Weather is the day-to-day condition of the atmosphere.

Climate is the average weather condition of a place over a long period.

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🌧️ Elements of Weather

• Temperature
• Humidity
• Rainfall
• Wind

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🌪️ Wind

Wind is moving air.

• Air moves from high pressure to low pressure
• Wind helps in dispersing seeds and pollen

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🌬️ Air Pollution

Air pollution occurs when harmful substances mix with air.

• Smoke from vehicles
• Factory gases
• Burning of fuels

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🌱 Prevention of Air Pollution

• Plant more trees
• Use public transport
• Reduce burning of fuels

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📌 Key Exam Points:
• Composition of air percentages are important
• Difference between weather and climate
• Troposphere & Stratosphere are frequently asked

Prepared by Shaktimatha Learning 🌟
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