Air Around Us Class 6 Notes Science Chapter 11

What is Air?

• The invisible gaseous medium around us, mainly constituted by oxygen and nitrogen is known as air. 
• It is through this air that we are able to carry out the process of respiration. 
• Air is transparent and colourless. 
• It occupies space and is present all around us.

Air

Is Air Present Everywhere Around Us?

• Air is present everywhere around us. 
• It has no colour and one can see through it. 
• Our earth is surrounded by a thin layer of air. 
• This layer extends up to many kilometres above the surface of the earth and is called atmosphere. 
• As we move higher in the atmosphere, the air gets rarer.

Atmosphere: The thin blanket of air surrounding the surface of the Earth is called the atmosphere

What is Air Made Up Of?

Air is a mixture of a number of gases and some other particles such as:

Water Vapour

• Air contains water vapour which helps maintain the water cycle. 
• When air comes in contact with cold surfaces, it is these vapours that turn into or condense into droplets of water. 
• The amount of water vapor in the air vary from place to place and time to time. 

Oxygen

• It is the oxygen in the air that helps humans and animals carry out the respiration process. 
• Oxygen is also required for fire to keep burning. If we were to keep an inverted tumbler covering a burning candle, the candle will go off in a few seconds because of the lack of oxygen-containing air due to the tumbler. 
• Dry air is said contain about 21% of oxygen.

Nitrogen

• Dry air is said to contain about 78% of nitrogen. 
• This component of air helps plants in their growth process.

Carbon dioxide

Dust and Smoke

• Dust particles are always present in the air, though their concentration varies depending on time and place.
• Dust particles can be observed in a beam of sunlight, especially in a dark room or during winter when sunlight filters through trees.
• When we breathe through our nostrils, fine hair and mucus in the nose help prevent dust particles from entering the respiratory system.
• Breathing through the mouth can allow harmful dust particles to enter the body, which is why it is advisable to breathe through the nose.
• Smoke is a byproduct of burning fuel and contains a mixture of gases and fine dust particles.
• Smoke is often harmful due to the presence of these fine particles and gases, which can affect health when inhaled.
• Long chimneys in factories are used to release smoke high into the air, keeping it away from people on the ground, but it can still affect birds flying in the sky.

How Does Oxygen become available to Animals and Plants Living in Water and Soil?

Characteristics of Air in Water

Air bubbles can be seen when water is heated

• Water contains dissolved air, which can be observed as tiny bubbles when water is heated.
• When water is heated, the dissolved air escapes first before the water turns into vapor and begins to boil.
• The dissolved oxygen in water is crucial for the respiration of aquatic animals.

Characteristics of Air in Soil

Air particles present in soil

• Soil contains air, which is necessary for the respiration of organisms living in it.
• When water is added to dry soil, the air present in the soil is displaced, visible as bubbles.
• Animals living in the soil create burrows and holes, which allow air to move in and out, providing oxygen for respiration.
• During heavy rains, water fills the spaces in the soil that usually contain air, forcing soil-dwelling organisms like earthworms to come to the surface to breathe.

Role of Oxygen in the Atmosphere

Despite the continuous consumption of oxygen by a large number of organisms, the atmosphere maintains its oxygen levels, indicating a natural process of oxygen replenishment.

How is Oxygen in the Atmosphere Replaced?

• Photosynthesis Process: Oxygen in the atmosphere is replaced through photosynthesis, a process where plants make their own food and release oxygen as a byproduct.
• Oxygen Production vs. Consumption: Although plants consume oxygen for respiration, they produce more oxygen during photosynthesis than they consume, resulting in a net production of oxygen.
• Interdependence of Plants and Animals: The balance of oxygen and carbon dioxide in the atmosphere is maintained through the interdependent processes of respiration in plants and animals and photosynthesis in plants.
• Vital Role of Plants: Plants are essential for life on Earth as they produce the oxygen necessary for the survival of animals, highlighting the critical interdependence between plants and animals.

Other Uses of Air:

• Windmills: Air is used to rotate windmills, which can draw water from tubewells, run flour mills, and generate electricity.

• Transportation: Air aids in the movement of sailing yachts, gliders, parachutes, and airplanes.
• Flight of Living Beings: Birds, bats, and insects can fly due to the presence of air.
• Seed and Pollen Dispersal: Air plays a crucial role in the dispersal of seeds and pollen from flowers, aiding plant reproduction.
• Role in Water Cycle: Air is essential in the water cycle, influencing the movement and distribution of water on Earth.
• It also helps in distributing the pollen and seeds from flowers of various plants.