Learn from School Connect Online in this chapter we will learn about  Air,which is present all around us.Air Around Us Class 6 Notes Science Chapter 15

Air is a mixture of gases. The different components of air includes – 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide, and about 1% water vapour. Air plays an important role in breathing and burning.

CBSE Class 6 Science Notes Chapter 15 Air Around Us

The different topics covered in CBSE Class 6 Science Chapter 15 are tabulated below:

Ex : 15.1 –  Is Air Present Everywhere Around Us?

Air is present all around us. We cannot see the air around us but we can feel its presence when the leaves rustle or branches sway.

Importance of Air

• We need air for breathing.
• All living beings need air for breathing.
• We need air to burn something.
• Life is possible on earth because of air.

Ex : 15.2 –  What Is Air Made Up Of?

Air is a mixture of different gases and particles; oxygen, water vapour, nitrogen, carbon dioxide, dust and smoke.

• Air is not one substance but is a mixture.
• Air is a mixture of some gases, water vapour and dust particles.
• The gases in the air are mainly nitrogen, oxygen, a small amount of carbon dioxide and some other gases.

Water vapours

• Air contains water vapours.
• When air comes in contact with a cool surface, it gets cooled and fog appears.
• The presence of water vapour in the air is important for the water cycle in nature.

Dust particles

• Air contains dust particles.
• The presence of dust particles in air varies from place to place and time to time.

Oxygen

• The component of air that supports burning is called oxygen.
• Oxygen is necessary for the survival of all living beings. It is required in respiration.
• Percentage of oxygen in the air is around 20.95%.

Nitrogen

• The major part of the air is nitrogen. It takes up four-fifth of the space (be around 78.11%) that air fills.
• Nitrogen does not support burning.

Carbon dioxide

• Carbon dioxide makes up a small component (0.03%) of air around us.
• It causes a feeling of suffocation.
• All materials, when they burn, consume oxygen and produce carbon dioxide.
• It is also produced along with water vapour during respiration.
• Plants need carbon dioxide for photosynthesis and to live.

Atmosphere

• Our earth is surrounded by air in the form of a thin layer. This thin layer is called the atmosphere.
• The atmosphere extends up to several kilometres.
• The air becomes thinner and thinner as we go high up from the surface of the earth.
• The atmosphere is quite active due to the movement of air, with respect to the earth.
• The processes like cloud formation, thundering, rain etc., occur in the atmosphere.

Ex : 15.3 –  How Does Oxygen Become Available To Animals And Plants Living In Water And Soil?

• In Plants:

Plants have tiny pores called stomata, found on the underside of a leaf.

Air containing carbon dioxide and oxygen enters the plant through these openings where it gets used in photosynthesis and respiration.

• In Animals:

All animals need to respire, be it a cockroach, a fish, or an elephant. It is just that they use different organs and mechanisms for respiration.

• In Aquatic Animals and Plants:

Most aquatic animals like fish, tadpole, crab, and shrimp have special organs for respiration called gills. Gills help to take in oxygen and give out carbon dioxide. Some aquatic animals like dolphins and whales come to the surface of the water regularly to take in air, since they breathe with the help of the lungs.Aquatic plants like Hydrilla also breathe in oxygen dissolved in water through their stomata.

• In Amphibians:

Amphibians like frogs, newts, and salamanders need breathing systems for both air and water. Crocodiles and alligators swim through water with part of their snout above the water surface to breathe easily through nostrils.

• In Birds:

Birds have an efficient respiratory system as they need high levels of oxygen during flight. Birds have a pair of lungs with air sacs that remain open all the time, so that air can easily pass through them.

• In Mammals:

Most mammals breathe with the help of lungs. They take in oxygen and give out carbon dioxide.

Ex : 15.4 –  How Is The Oxygen In The Atmosphere Replaced?

• Organisms usually come together where each benefits from the other.
• We get oxygen and other products from plants and they get not only carbon dioxide but other advantages from us.
• This is in the form of a cycle. Respiration and photosynthesis lead to recycling of oxygen and carbon dioxide in the environment.

Conclusion :

• All living organisms need air to survive. Air cannot be seen but can be felt when it moves.
• Air is a mixture of several gases.
• Oxygen is needed for respiration. Carbon dioxide is given out as a by-product after respiration.
• Insects take in air with the help of tiny holes in their bodies called spiracles; earthworms breathe through their skin, which is kept moist with the help of a substance called mucus.
• Some aquatic animals like whales and dolphins as well as mammals breathe with the help of lungs.
• Amphibians like frogs breathe with the help of lungs, when on land. In water, these animals breathe with the help of their moist skin.
• Birds breathe through lungs and air sacs that are open all the time.
• There are several causes of air pollution: excessive burning of fuels like wood, coal, and petroleum, machines releasing gases, vehicles releasing smoke, and several types of harmful gases released by industries.

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