AIR AROUND US

What is air?

Air is a mixture of gases and dust particles. It is a gas in which living things breathe and live.

Air is a matter it has volume and mass. It creates atmospheric pressure.

Properties of air

• Air is colorless, tasteless and odourless gas.
• Air occupies space.
• Air dissolves in water.
• Air has mass.

Air Composition

Air contains mainly oxygen, nitrogen, and remaining includes noble gases, carbon dioxide, water vapour, traces of other gases and dust particles.

Air contains 28% Oxygen and 78% Nitrogen.

Oxygen helps in burning.

It is used by living things to respire.

Nitrogen helps in growth of plants.

Air contains 0.003%of carbon dioxide.

Plants produce carbon dioxide during respiration.

Uses of Air

• Air helps in the movement of sailing yachts, Parachutes and aircraft.
• Air also helps in dispersal of seeds.
• We cannot hear the sounds in the absence of air.
• Air is also useful for playing several musical instruments.

 Atmosphere

The earth’s surface is covered with a thick blanket of air is called the atmosphere.

The atmosphere is divided into five distinct layers.

1.Troposhere: This is the first layer to the atmosphere which is nearest to the surface and is responsible for whether condition.

2.Stratosphere: This is layer just above the troposphere which contains the ozone layer and where the aeroplanes fly and is also home to most of clouds.

3.Mesosphere: This is the third and the coldest layer of our atmosphere.

4.Thermosphere: This is the fourth and one of the hottest layers of the earth where temperature go to a 1500. The air in this layer is very thin and about 99.9% of the atmosphere is said to lie below this particular layer.

5.Exosphere: This is the outermost layer of the atmosphere where molecules and atoms escape into the space.

Water vapour

Image Credit: https://climatekids.nasa.gov/cloud-formation/

Air contains some amount 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 is produced due to the burning of fossil fuels. It contains carbon dioxide and other gases as well as dust particles. Both dust and smoke are harmful to living organisms and the environment.

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 system 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.

 How is the oxygen in the atmosphere replaced?

The oxygen of air which is consumed by animals and plants in respiration and in the burning of fuels is constantly replaced by plants through the process of photosynthesis.

Photosynthesis is a process by which plants make their food and oxygen is produced.

EXAM RELATED QUESTIONS

1.Why is air considered as a mixture?

Ans. Air contains oxygen and nitrogen as its major constituents of air. These gases retain their properties in air. So, the air is called a mixture.

 2.What happens if the percentage of carbon dioxide increases in the air?

Ans. The increased percentage of carbon dioxide will cause greenhouse effect, it will not allow the hot rays of sun to escape from the atmosphere after reflection once they enter the earth’s atmosphere, increasing the temperature of earth, ice or mountains will melt and water level will rise.

3.Why is carbon dioxide gas used to extinguish fire?

Ans. It is because carbon dioxide does not support combustion. When sprayed on burning object it stops the supply of oxygen and extinguish fire. 

4.Why do we see the sky and air clear and clean after rainfall?

Ans. Sky becomes clear after first rain because the dust particles in the atmosphere settles down with the rain drops. So, sky appears clear and clean.

5.What is the composition of air?

Ans. Atmospheric air comprises Oxygen (21%), Nitrogen (78%) carbon dioxide, water vapour and pollutants (1%) like dust and smoke.

6.What is humidity?

Ans. The amount of water vapour present in the air is called humidity.

7.Why do you think mountaineer carry oxygen cylinder with them, while climbing high mountains?

Ans. There is less oxygen at high places like mountains, so they carry oxygen cylinder with them to breathe there.

8.Why we not breathe through our mouth?

Ans. If we breathe through our mouth then the dust particles present in the air will enter our body and will cause harmful disease.

9.List any 5 activities that are possible due to presence of air?

Ans. Respiration, burning, photosynthesis, combustion of fuels and power generation from windmills.

10.Name a device which uses wind energy to generate electricity?

Ans. Windmills use the wind energy to convert wind energy into electrical energy.