Air Around Us
This chapter explains the composition of air, presence of air everywhere, properties of air, components including oxygen, nitrogen, carbon dioxide, water vapour, and dust particles, and the importance of air for respiration, burning, and life.
Quick Revision: Air Around Us
- Air is Everywhere: Air occupies space, has no colour, is transparent, and is present all around us.
- Atmosphere: The thin layer of air surrounding Earth, extending many kilometres above the surface.
- Composition of Air: Mixture of gases: Nitrogen (~78%), Oxygen (~21%), Carbon dioxide, water vapour, and other gases (~1%).
- Oxygen: Supports burning and is essential for respiration. Plants produce oxygen during photosynthesis.
- Nitrogen: Major component of air (about 78%) that does not support burning.
- Carbon Dioxide: Small component used by plants for photosynthesis. Excess can cause suffocation.
- Water Vapour: Present in air; condenses on cool surfaces; essential for water cycle.
- Dust Particles: Present in air; visible in sunlight beam; can be harmful when inhaled.
- Air in Water: Dissolved air in water provides oxygen for aquatic animals and plants.
- Air in Soil: Spaces in soil contain air for organisms living underground and plant roots.
- Oxygen Balance: Plants produce oxygen through photosynthesis, consuming carbon dioxide; animals consume oxygen and release carbon dioxide.
- Uses of Air: Windmills, sailing, flying, seed dispersal, water cycle, and more.
Chapter Summary: Air Around Us
Air is a mixture of gases that surrounds the Earth, forming the atmosphere. It is transparent, colourless, and occupies space. The major components of air are nitrogen (about 78%) and oxygen (about 21%). The remaining 1% includes carbon dioxide, water vapour, and other gases, along with dust particles.
Oxygen is essential for respiration and burning. Nitrogen does not support burning. Carbon dioxide is used by plants for photosynthesis. Water vapour in air is important for the water cycle. Air also contains dust particles which can be seen in a beam of sunlight. Air is dissolved in water, providing oxygen to aquatic life. Soil also contains air in its pores, allowing organisms and plant roots to respire. Plants and animals help each other in maintaining the balance of oxygen and carbon dioxide in the atmosphere through photosynthesis and respiration.
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