NCERT Class 6th Science Chapter 11 Air Around Us Notes

𝗤𝗨𝗜𝗭𝗘𝗧

NCERT Class 6th Science Chapter 11 Air Around Us Notes

Introduction: The Presence of Air

  • Air is essential for life: As discussed in Chapter 6, all living things require air to survive.
  • Invisible but felt: Although air is invisible, its presence can be felt through various activities like rustling leaves, swaying clothes, and fluttering pages.
  • Moving air: Air in motion is referred to as wind. Examples include winnowing (separation of grains using air), and the movement of a kite, which are all influenced by moving air.

Is Air Present Everywhere Around Us?

  • Observation with a bottle:

    • Activity 2: When an open, empty bottle is turned upside down and immersed in water, bubbles appear when tilted, showing that the bottle was not empty but filled with air.
    • Conclusion: Air occupies space and is present everywhere, even in seemingly empty spaces.
    • Air is transparent: Air has no color and is transparent, making it invisible but still present.

  • Atmosphere:

    • Thin layer around Earth: Air surrounds Earth in a layer called the atmosphere, extending several kilometers above the surface.
    • Air gets thinner with altitude: As altitude increases, air becomes rarer, which is why mountaineers carry oxygen cylinders when climbing high mountains.

What is Air Made Up Of?

  • Air is a mixture of gases: Initially thought to be a single substance, air is now known to be a mixture of several gases.

    • Water Vapour:

      • Role in the water cycle: Water vapour in the air is crucial for the water cycle. It condenses on cool surfaces, forming water droplets.

    • Oxygen:

      • Supports burning: Through Activity 3 (two candles, one covered by a glass), it is demonstrated that oxygen supports burning. The candle under the glass extinguishes due to the depletion of oxygen.

    • Nitrogen:

      • Major component of air: Even after the candle extinguishes, air remains in the glass, indicating the presence of nitrogen, which does not support burning.

    • Carbon Dioxide:

      • Produced by respiration and burning: Carbon dioxide is a small but essential component of air. It is produced by animals during respiration and by burning materials.
      • Suffocation in enclosed spaces: Accumulation of carbon dioxide in a closed room can cause suffocation.

    • Dust and Smoke:

      • Produced by burning fuels: Smoke contains gases and dust particles, often harmful, which is why factories use tall chimneys to release smoke at a height.
      • Dust particles in air: Dust particles are always present in the air, visible in beams of sunlight entering a dark room.

  • Composition of air:

    • Major gases: Nitrogen and oxygen make up 99% of the air.
    • Minor components: Carbon dioxide, water vapour, and other gases make up the remaining 1%.

How Does Oxygen Become Available to Animals and Plants Living in Water and Soil?

  • Dissolved air in water:

    • Activity 5: Heating water reveals tiny bubbles, which are air escaping from the water. This air, particularly oxygen, is used by aquatic animals for respiration.

  • Air in soil:

    • Activity 6: When water is poured onto dry soil, bubbles emerge, showing that air is present in the soil.
    • Respiration in soil organisms: Animals living in the soil and plant roots use this air for respiration.
    • Effect of rain: Heavy rains can fill the air spaces in the soil with water, forcing soil organisms like earthworms to come to the surface for air.

How is the Oxygen in the Atmosphere Replaced?

  • Photosynthesis:
    • Process: Plants produce oxygen during photosynthesis, replenishing the oxygen used by animals and plants during respiration.
    • Balance of gases: This process maintains the balance of oxygen and carbon dioxide in the atmosphere.
    • Interdependence of plants and animals: The exchange of gases between plants and animals highlights their interdependence.

Importance of Air Beyond Breathing

  • Windmills:
    • Uses: Wind energy is harnessed by windmills to draw water, grind grain, and generate electricity.
  • Aviation and Movement:
    • Airplanes and gliders: Air is essential for the flight of airplanes, gliders, and parachutes.
    • Birds and insects: Air enables birds, bats, and insects to fly.
  • Seed Dispersal:
    • Plants: Air aids in the dispersal of seeds and pollen, helping in plant reproduction.
  • Water Cycle:
  • Role: Air plays a crucial role in the water cycle by transporting water vapour.

Additional Uses of Air

  • Air in Daily Life:

    • Ventilation: Air is vital for maintaining indoor air quality in homes, offices, and other buildings. Proper ventilation ensures that fresh air replaces stale air, reducing the concentration of pollutants and carbon dioxide.
    • Cooking: In traditional cooking methods, air plays a significant role in burning fuels like wood and charcoal, which require oxygen to maintain the flame.

  • Wind as a Source of Energy:

    • Renewable Energy: Wind energy is a renewable resource, and wind turbines convert kinetic energy from the wind into mechanical or electrical energy.
    • Advantages: Wind energy is clean, does not produce greenhouse gases, and can help reduce dependence on fossil fuels.

Air and the Water Cycle

  • Evaporation and Condensation:

    • Evaporation: Air absorbs heat from the sun, causing water from oceans, rivers, lakes, and other bodies of water to evaporate into water vapour.
    • Condensation: As the water vapour rises and cools, it condenses to form clouds, eventually leading to precipitation (rain, snow, etc.).

  • Precipitation:

    • Role of Air: Air currents influence the movement of clouds, determining where and when precipitation occurs. This process is essential for replenishing water sources on Earth.

Air Quality and Pollution

  • Sources of Air Pollution:

    • Industrial Emissions: Factories and industries release pollutants, including harmful gases and particulate matter, into the air.
    • Vehicle Emissions: Cars, trucks, and other vehicles emit pollutants like carbon monoxide, nitrogen oxides, and hydrocarbons, contributing to air pollution.
    • Burning of Fossil Fuels: The burning of coal, oil, and natural gas for energy releases pollutants and greenhouse gases into the atmosphere.

  • Effects of Air Pollution:

    • Health Impacts: Prolonged exposure to polluted air can lead to respiratory problems, cardiovascular diseases, and other health issues.
    • Environmental Impacts: Air pollution can lead to acid rain, which harms aquatic ecosystems, soil, and vegetation. It also contributes to global warming by increasing the concentration of greenhouse gases in the atmosphere.

  • Reducing Air Pollution:

    • Clean Energy Sources: Using renewable energy sources like solar, wind, and hydropower can help reduce air pollution.
    • Afforestation: Planting more trees and preserving forests can help absorb carbon dioxide, a major greenhouse gas, from the atmosphere.
    • Regulations and Policies: Governments can implement regulations and policies to control emissions from industries and vehicles, promoting cleaner air.

The Importance of Oxygen in Various Ecosystems

  • Aquatic Ecosystems:

    • Dissolved Oxygen: Oxygen dissolved in water is crucial for the survival of fish and other aquatic organisms. Low levels of dissolved oxygen can lead to hypoxic conditions, which are harmful to marine life.

  • Soil Ecosystems:

    • Soil Aeration: The presence of air in soil is essential for the respiration of microorganisms and plant roots. Well-aerated soil supports healthy plant growth and maintains soil fertility.

  • Human Activities and Oxygen:

    • Medical Uses: Oxygen is used in hospitals and medical facilities to treat patients with respiratory issues. Oxygen therapy is essential for patients with conditions like chronic obstructive pulmonary disease (COPD) and pneumonia.

Air and Climate

  • Climate Regulation:

    • Temperature Control: Air plays a vital role in regulating Earth's temperature by distributing heat from the sun across the planet through air currents and weather patterns.
    • Greenhouse Effect: Gases in the air, like carbon dioxide and methane, trap heat in the atmosphere, keeping Earth warm enough to support life. However, excessive greenhouse gases can lead to global warming.

  • Weather Patterns:

    • Air Pressure: Differences in air pressure drive wind and influence weather patterns. High and low-pressure systems determine whether an area will experience sunny weather, rain, or storms.
    • Storms and Hurricanes: Strong winds in storms and hurricanes are driven by differences in air pressure and temperature. Understanding air movements helps meteorologists predict and track these weather events.

Summary and Conclusion

  • Air's Ubiquity: Air is present everywhere on Earth, filling all spaces and surrounding all living things. Despite being invisible, its presence is vital for life and numerous natural processes.
  • Mixture of Gases: Air is a mixture of nitrogen, oxygen, carbon dioxide, water vapour, and other gases. These components play essential roles in sustaining life and supporting various ecological processes.
  • Oxygen's Role: Oxygen is crucial for respiration in animals and plants, and it is continuously replenished in the atmosphere through photosynthesis by plants.
  • Human Impact: Human activities, such as burning fossil fuels and industrial emissions, can significantly impact air quality, leading to pollution and environmental changes.
  • Air and Life Interdependence: The balance of gases in the air, the regulation of Earth's temperature, and the support of life through respiration and photosynthesis highlight the interdependence of living organisms and the atmosphere.

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