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Chapter: 4th Science : Term 3 Unit 3 : Air We Breathe

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Air We Breathe (Term 3 Chapter 3 | 4th Science)



I. Choose the correct answer.


1. Air is a ___________.

 (a) Mixture

(b) Compound

(c) Complex

Answer: (a) Mixture


2. Percentage of Oxygen in air is about ___________%.

 (a) 21

(b) 78

(c) 1

Answer: (a) 21


3. Root nodules of some plants contain ___________.

 (a) Oxygen

(b) Nitrogen

(c) Neon

Answer: (b) Nitrogen


4. The major cause of air pollution is ___________.

 (a) Waste

(b) Smoke

(c) Water vapour

Answer: (b) Smoke


II. Who am I?

1. I am a mixture of gases.


2. I give you oxygen.


3. I am not the supporter of burning.

Carbon dioxide

4. You can help me to decrease pollution by riding on me.



III. Write ‘True‛ or ‘False‛.

1. Plants need nitrogen for their growth. True

2. Air is made up of oxygen only. False

3. The gas used for burning things is Argon. False

4. Carbonated drinks are bad to health. True


IV. Math the following.

1. Nitrogen - Air pollution

2. Balloon - Smoke and fog

3. Smog - 78%

4. Lung cancer – Air


1. Nitrogen - 78%

2. Balloon - Air

3. Smog - Smoke and fog

4. Lung cancer – Air pollution


V. Fill in the blanks.

1. Air is a mixture of many gases.

2. Amount of carbon dioxide in the air is 0.03 %.

3. We inhale oxygen gas.

4. Carbon dioxide is used in fire extinguishers.


VI. Answer the following questions in brief.

1. What are the importance of air in our daily life?

• Oxygen present in air is needed for respiration.

• We can speak and hear the sound only when there is air around.

• Air helps in the dispersal of seeds for plant reproduction.

• Monsoon and rain occurs due to the wind action.

• Air regulates the atmospheric temperature.

2. What are the components of air?

Nitrogen - 78%

Oxygen - 21%

Carbon dioxide - 0.03%

Argon and other gases - 0.07%

3. What are the adverse effects of air pollution?

Global warming, Formation of smog, Formation of acid rain, Aerosol formation, Depletion of Ozone

4. List uses of oxygen.

1. All living things use oxygen for breathing.

2. Oxygen is essential for burning.

3. Oxygen cylinders are used in hospitals to enable the patients to breathe when they cannot breathe normally.

4. Oxygen is used in gas welding.


VII. Give short answers.

1. How can we reduce air pollution?

Air pollution can be reduced by the following steps.

1. Alternative source of energy (E.g. Solar energy) should be used.

2. Air filters should be used to prevent harmful gases mixing with air.

3. Smoke emission test and certification of motor vehicles must be enforced.

4. More trees should be planted to absorb carbon dioxide.

2. What are the diseases caused due to air pollution?

Air pollution has bad impact on human health. When the pollutants increase in air, they irritating in the eyes, nose and throat. Air pollution can also produce wheezing, coughing and breathing problems in humans.

1. Respiratory diseases. Eg. Flu, Tuberculosis

2. Cardiovascular damage

3. Fatigue, headaches and anxiety

4. Nervous system damage

3. List out the uses of carbon dioxide.

1. Carbon dioxide helps plants in photosynthesis.

2. It is used in fire extinguishers.

3. It is used in refrigerators as dry ice for cooling purposes.

4. It is used to make plastics and polymers.



Take a squeezable bottle. Make a hole on the lid and close the bottle tightly. Bring the bottle near your face and press the bottle. What do you feel?

Let us do

Tick the objects which have air in them.

Let us do

Tick the object which gives out water vapour.


Write the percentage of the gases present in air.


You might have seen some huge colourful balloons flying high in malls. Those balloons are filled with nitrogen gas. Write the reason for filling nitrogen gas in balloons.

Nitrogen is an inert gas. It is similar to air but it is slightly lighter than air. So when there is no necessity to lift the balloon very high, we use nitrogen gas.


Classify the following.

( Dog, cat, coconut tree, monkey, brinjal plant, papaya plant)


Look at the path of light rays entering through window of your home/school. You can see lot of tiny particles suspended and moving in the air. These are dust particles. You can also test the same with the help of a torch light in darkness.


Tick the causes of global warming


 Go by walk or use a bicycle to nearby places.

 Plant more trees.


Write slogans on harmful effects of air pollution in a chart and stick it on the display board

1. Polluted air, harms our heir.

2. Pollution kills, brings all ills

3. Smoke and fog like rabid dog.

4. Bike race thrills but pollution kills.

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