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Lesson 26: Composition of the Atmosphere Gases in air Percentages (intro) Importance of oxygen, nitrogen, CO₂
Year 8 • Chemistry
Lesson 26: Composition of the Atmosphere
In this lesson, students learn what gases make up the air around us, their approximate percentages, and why oxygen, nitrogen, and carbon dioxide are essential for life and the environment.
Lesson Objectives
- Identify the main gases in air.
- Recall the approximate percentage of each gas.
- Explain why oxygen, nitrogen, and carbon dioxide are important.
- Relate atmospheric gases to everyday life.
1. What Is the Atmosphere?
The atmosphere is a layer of gases that surrounds the Earth. It protects life and provides the air we breathe.
[ Image Placeholder – Earth and Atmosphere ]
Key ideas:
• Air is a mixture of gases
• The atmosphere keeps Earth warm
• It protects us from harmful radiation
• Air is a mixture of gases
• The atmosphere keeps Earth warm
• It protects us from harmful radiation
2. Gases in the Air
Air is made of different gases mixed together.
[ Image Placeholder – Gases in Air Diagram ]
Main gases in air:
• Nitrogen (~78%)
• Oxygen (~21%)
• Argon (~1%)
• Carbon dioxide (~0.04%)
• Nitrogen (~78%)
• Oxygen (~21%)
• Argon (~1%)
• Carbon dioxide (~0.04%)
These values are approximate and help us compare amounts.
3. Importance of Oxygen
Oxygen is essential for most living organisms.
[ Image Placeholder – Breathing and Oxygen ]
• Needed for breathing
• Used in respiration to release energy
• Supports burning (combustion)
• Used in respiration to release energy
• Supports burning (combustion)
4. Importance of Nitrogen and Carbon Dioxide
Other gases in the atmosphere are also very important.
[ Image Placeholder – Nitrogen and CO₂ Uses ]
Nitrogen:
• Helps plants grow
• Makes air less reactive
• Helps plants grow
• Makes air less reactive
Carbon dioxide:
• Used by plants in photosynthesis
• Helps keep Earth warm
Practice Questions
A. Fill in the Blanks
- The atmosphere is a layer of __________ around Earth.
- The most common gas in air is __________.
- Oxygen makes up about __________% of air.
- Plants use __________ dioxide in photosynthesis.
- Nitrogen helps make air less __________.
B. True or False
- Air is a pure substance.
- Oxygen is needed for breathing.
- Nitrogen makes up most of the air.
- Carbon dioxide is the most common gas in air.
- The atmosphere protects Earth.
C. Short Answer
- What is the atmosphere?
- Name two gases found in air.
- Why is oxygen important?
- Why is nitrogen useful in the air?
- Give one role of carbon dioxide.
✅ Show Answer Key
A. Fill in the Blanks
- gases
- nitrogen
- 21
- carbon
- reactive
B. True or False
- False
- True
- True
- False
- True
C. Short Answer
- A layer of gases surrounding Earth.
- Nitrogen, oxygen (any two).
- It is needed for breathing.
- It reduces reactions and helps plants.
- Used in photosynthesis / keeps Earth warm.
© Aviate Learning – Composition of the Atmosphere (Year 8)
🌍 Interactive Composition of the Atmosphere
The pie chart shows the main gases in the air and their approximate percentages.
Click or hover over each section to learn more.
🔵 Nitrogen – 78%
🟢 Oxygen – 21%
🟣 Argon – ~1%
🟠 Carbon Dioxide – ~0.04%
Hover over a section of the chart to learn about that gas.