Air Around Us Class 6 Notes

Understanding Air and the Atmosphere

Air is a mixture of gases that surrounds the entire Earth. Although air is invisible, transparent, and tasteless, it is a physical substance that occupies space and has mass. The thin blanket of air that surrounds the Earth is known as the atmosphere. This atmospheric layer extends up to many kilometres above the surface of the Earth and becomes thinner as we go higher up. This is the reason why mountaineers carry oxygen cylinders when climbing high mountains. Moving air is called wind, which plays a vital role in turning windmills, dispersing seeds, and guiding the flight of birds and gliders. A weather cock or wind vane is used to show the direction in which the air is moving at a particular place.

Essential Exam Glossary

Atmosphere

The thick, protective blanket of air that surrounds the Earth and is held in place by the Earth's gravity.

Wind

Air in motion. It helps in moving gliders, sailboats, and wind turbine blades.

Respiration

The biological process by which living organisms take in oxygen and release carbon dioxide to produce energy.

Photosynthesis

The process by which green plants prepare their food using sunlight, carbon dioxide, water, and chlorophyll, releasing oxygen as a byproduct.

Humidity

The measure of the amount of water vapour present in the air.

Combustion

The chemical process of burning, which requires oxygen to proceed and produces heat and light.

Composition of Air: Major Components Compared

Key Demonstrations and Observations

• {"title":"Experiment 1: Air Occupies Space","description":"Take an empty open bottle and push it upside down into a bucket filled with water. Water does not enter the bottle because it is filled with air. Tilt the bottle slightly, and you will see bubbles escaping. Water then rushes in to fill the empty space left by the escaping air."}
• {"title":"Experiment 2: Air is Dissolved in Water","description":"Heat a small amount of water in a beaker. Before it starts boiling, look closely at the inner surface of the vessel. You will notice tiny bubbles clinging to the sides. These bubbles are made of air that was dissolved in the water, escaping as heat increases."}
• {"title":"Experiment 3: Air is Present in Soil","description":"Take a dry lump of soil in a beaker and pour water over it. You will observe bubbles bubbling up. This happens because water displaces the air trapped in the tiny spaces between the soil particles."}

Must-Remember Revision Points

• Air is a mixture, not a single element or compound.
• The major components of air are Nitrogen (~78%) and Oxygen (~21%). The remaining 1% consists of Carbon dioxide, noble gases, water vapour, and dust particles.
• Oxygen is essential for respiration in all living things, while plants need carbon dioxide for photosynthesis.
• Aquatic animals use dissolved oxygen in water for respiration through specialized organs like gills.
• Soil-dwelling organisms (like earthworms) breathe air trapped between soil particles. Heavy rains block these air pockets, forcing earthworms to come out of the soil to breathe.
• Plants and animals are interdependent. Plants produce oxygen during photosynthesis, which is used by animals for respiration. In turn, animals produce carbon dioxide, which is used by plants.
• The ozone layer, present in the upper atmosphere, protects living organisms from harmful ultraviolet (UV) radiation coming from the Sun.
• Windmills utilize wind energy to pump water, generate electricity, and grind grain.

High-Yield Exam Tips & Common Traps

1. The Candle Experiment Trick: If an exam question asks how to prove that air supports burning, explain the inverted glass tumbler experiment. Do not forget to state that when the oxygen inside the glass is completely consumed, the flame goes out.
2. Respiration vs. Photosynthesis: Students often make the mistake of writing that plants only breathe carbon dioxide. Remember: Plants respire (breathe in oxygen, release CO2) all the time (day and night). They perform photosynthesis (absorbing CO2, releasing oxygen) only in the presence of sunlight.
3. Mountaineers carry Oxygen: If asked why mountaineers carry oxygen cylinders, clearly write two points: (a) The atmosphere gets thinner as altitude increases. (b) The amount of oxygen available for breathing decreases significantly at high altitudes.

Quick Chapter Revision Check

• Which gas in the atmosphere does not support burning? Nitrogen gas is the major component of air that does not support burning.
• How do plants and animals maintain the balance of oxygen and carbon dioxide in the atmosphere? Animals consume oxygen and release carbon dioxide during respiration. Green plants consume carbon dioxide and release oxygen during photosynthesis. This cycle maintains the balance of both gases in nature.
• Why do earthworms come out of the soil only during heavy rains? During heavy rains, water fills up all the air spaces and pores in the soil. Because there is no air left to breathe underground, earthworms must come to the surface for respiration.
• What is the role of a weather cock? A weather cock (or wind vane) is an instrument used to show the direction in which the wind is blowing at a particular place.

Frequently Asked Questions