NCERT Summary: Air around Us | Science Class 6 PDF Download

What is air?

1. Air is a mixture of gases and dust particles. It is a clear gas in which living things breathe and live.
2. Air is a matter it has volume and mass. It creates atmospheric pressure.
3. In vacuum there in no air present over there.

Atmosphere: It is a thick layer of air surrounding the earth’s surface is known as atmosphere.
Wind: The moving air is known as wind.

Air composition

• Air contains mainly oxygen, nitrogen and remaining includes noble gases, carbon dioxide, water vapour, traces of other gases and dust particles.
• Oxygen and nitrogen: air contains 78% nitrogen, 21% oxygen and 1 % other gases and water vapour.
• Oxygen helps in burning. It is used by living things to respire,
• Nitrogen helps in growth of plant.

Carbon dioxide

• Air contains 0.003% of carbon dioxide.
• Carbon dioxide is also produced during burning.
• Plants and animals produce carbon dioxide during respiration.

Water vapour

• Air contains some amounts of water vapour depends upon the weather of a place.
• Water vapour presence is very important for water cycle in nature.

Dust and Smoke

• Smoke contains few gases with fine dust particles and is often harmful.

How does oxygen become available for all living beings?

Plants

• They use carbon dioxide of the air to make their own food by a process called photosynthesis.

Aquatic animals

• Most aquatic animals have special organs for respiration called gills. They use oxygen from air dissolved in water.

Amphibians

• Some amphibians like frogs, salamanders need breathing systems for both water and air.
• Frogs have lungs to breathe air when on land. In water, frogs breathe with their moist skin.

Birds

• They have pair of lungs with air sacs which is open all the time, because birds need high level of oxygen during flight.

Mammals

• They breathe with the help of lungs. They take oxygen and give out carbon dioxide.

Properties of oxygen

• Air is colourless
• Air is transparent
• It is essential for life
• It occupies space
• It present everywhere including water and soil
• It exerts pressure