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Year 8 Science (UK)
The Composition of the Atmosphere | Year 8 Science UK
🌍 The Composition of the Atmosphere
UK Year 8 Science – Detailed Lecture Notes (with UK-based examples)
🌫️ What is the Atmosphere?
The atmosphere is a thick blanket of gases that surrounds the Earth. It is held in place by gravity, just like the air stays around us instead of floating away into space.
Without the atmosphere:
- There would be no oxygen to breathe
- No rain or clouds
- Earth would be too cold at night and too hot during the day
- Harmful radiation from the Sun would reach the ground
🇬🇧 UK Example: Life in the UK would not be possible without the atmosphere —
from people breathing in London to crops growing across England and Scotland.
🧪 What is Air Made Of?
Air is not one gas. It is a mixture of gases.
📊 Composition of the Atmosphere (Dry Air)
| Gas | Percentage | Explanation |
|---|---|---|
| Nitrogen (N₂) | 78% | Makes air stable and less reactive |
| Oxygen (O₂) | 21% | Needed for breathing and burning |
| Argon (Ar) | 0.9% | Unreactive gas |
| Carbon Dioxide (CO₂) | 0.04% | Used by plants |
| Other gases | Tiny amounts | Neon, helium, methane, ozone |
🟦 Nitrogen – The Most Abundant Gas (78%)
Nitrogen makes up most of the air, but we do not breathe it in for energy.
- Dilutes oxygen, preventing fires from starting easily
- Used by plants (through soil bacteria) to make proteins
🇬🇧 UK Example: UK farmers use nitrogen fertilisers to grow crops such as wheat and barley.
📌 Nitrogen keeps the atmosphere safe and balanced.
🟩 Oxygen – The Gas of Life (21%)
Respiration
All living things use oxygen to release energy from food.
🇬🇧 UK Example: During PE lessons, breathing increases because the body needs more oxygen.
Burning
Fires need oxygen to keep burning.
🇬🇧 UK Example: Gas cookers in UK homes burn because oxygen supports combustion.
Too much oxygen → fires everywhere
Too little oxygen → living things cannot survive
Too little oxygen → living things cannot survive
🟨 Carbon Dioxide – Small but Important (0.04%)
- Used by plants in photosynthesis
- Helps keep Earth warm (greenhouse effect)
🇬🇧 UK Example: Trees in Hyde Park absorb CO₂ and release oxygen, improving air quality.
🇬🇧 Human Impact: Cars on the M25 and power stations increase CO₂ levels.
🟪 Argon and Other Gases
Argon is an inert gas that does not react easily.
🇬🇧 UK Example: Argon is used in double-glazed windows to reduce heat loss.
- Neon – signs
- Helium – balloons
- Methane – fuel and greenhouse gas
- Ozone – protects from UV rays
💧 Water Vapour – The Variable Gas
- Amount changes daily
- Warm air holds more water vapour
- Causes clouds, rain, snow and fog
🇬🇧 UK Example: The UK’s rainy weather is caused by moist air from the Atlantic Ocean.
🏔️ Layers of the Atmosphere (Basic Awareness)
| Layer | What Happens Here? |
|---|---|
| Troposphere | Weather, clouds, rain |
| Stratosphere | Ozone layer |
| Mesosphere | Meteors burn up |
| Thermosphere | Satellites |
| Exosphere | Space begins |
📌 Year 8 reminder: Focus mainly on composition, not detailed layers.
🌍 Human Activities and Air Pollution (UK)
- Cars and buses
- Factories
- Burning fossil fuels
- Deforestation
🇬🇧 UK Example: London’s ULEZ helps reduce air pollution.
🧠 Exam Tips
- Remember: 78% nitrogen, 21% oxygen
- Explain why each gas is important
- Use UK examples for higher marks
✨ Final Summary
- The atmosphere is a mixture of gases
- Nitrogen is the largest part
- Oxygen supports life and burning
- Carbon dioxide supports plant life
- Water vapour affects weather
- Human activity can change the atmosphere