Chapter 11 of 18
Revision Notes
Composition and Structure of the Atmosphere — Revision Notes
ICSE · Class 9 · Geography
Composition and Structure of the Atmosphere revision notes for ICSE Class 9 Geography: 4 topics in quick points.
84 questions35 flashcards5 concepts
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Key Topics to Revise
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1. Composition of the Atmosphere
- Nitrogen and oxygen are the two main gases in clean dry air.
- Nitrogen makes up 78% of the atmosphere and oxygen makes up 21%.
- Together, nitrogen and oxygen make up about 99% of clean dry air.
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2. Structure of the Atmosphere
- On the basis of structure, the atmosphere has four main layers: troposphere, stratosphere, ionosphere, and exosphere.
- Troposphere is the lowermost layer where we live.
- Almost all weather phenomena take place in the troposphere.
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3. Ozone in the Stratosphere
- Ozone is made of three oxygen atoms, while ordinary oxygen has two atoms.
- Ozone forms in the upper stratosphere when ultraviolet radiation breaks an oxygen molecule into atoms that combine to form ozone.
- Ozone absorbs harmful ultraviolet radiation from the Sun.
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4. Greenhouse Effect and Global Warming
- Almost all the energy available to the Earth and its atmosphere comes from the Sun.
- Direct ultraviolet rays of the Sun are extremely harmful for living beings.
- Greenhouse gases include carbon dioxide, methane, nitrous oxide, and water vapour.
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Full NotesKey Concepts
The atmosphere is a relatively thinNitrogen makes up 78% of cleanWater vapour is a colourlessThe troposphere is the lowermost atmosphericThe tropopause is the upper boundary
Frequently Asked Questions
What are the important topics in Composition and Structure of the Atmosphere for ICSE Class 9 Geography?
Key topics in Composition and Structure of the Atmosphere include Composition of the Atmosphere, Structure of the Atmosphere, Ozone in the Stratosphere, Greenhouse Effect and Global Warming. Study these first, then practise questions on each for Class 9 exams.
How should I revise Composition and Structure of the Atmosphere for Class 9 exams?
Learn the core ideas first, then work through the 84 practice questions on Composition and Structure of the Atmosphere. Revise definitions regularly and use flashcards for quick recall before the exam.
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