Chapter 7 · ICSE Class 7 Chemistry (Selina Concise)

Air and Atmosphere

Deepen your understanding of the atmosphere's layers, composition of air, and the greenhouse effect.

💨 Chapter 7

The detailed composition of air: nitrogen, oxygen, and trace gases A pie chart showing air is about 78 percent nitrogen, 21 percent oxygen, and about 1 percent other gases including carbon dioxide and argon Nitrogen 78% Oxygen 21% + ~1% CO₂, argon & other trace gases
7.1

Layers of the Atmosphere

The atmosphere has layers: the troposphere (closest to Earth, where weather occurs), the stratosphere (contains the ozone layer), and layers beyond.

1

Which layer of the atmosphere contains the ozone layer?

The stratosphere

2

Which layer of the atmosphere is where weather occurs?

The troposphere

7.2

The Greenhouse Effect

Greenhouse gases like carbon dioxide trap heat in the atmosphere, warming the Earth. Excessive greenhouse gases contribute to global warming.

1

Name a greenhouse gas.

Carbon dioxide (or methane, water vapour)

2

Why is an increase in carbon dioxide linked to global warming?

More carbon dioxide traps more heat in the atmosphere, gradually raising Earth's average temperature

Practice

Exercises

1. Name the layer of the atmosphere closest to Earth.

2. Which layer contains the ozone layer?

3. Name a greenhouse gas.

4. What is the greenhouse effect?

5. Why is the ozone layer important?

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