Samacheer Kalvi 6th Science Term 2 Solutions Chapter 4 Pdf

Samacheer Kalvi 6th Science Term 2 Solutions Chapter 4 Pdf

Tamilnadu Board Samacheer Kalvi 6th Science Term 2 Solutions Chapter 4: Tamilnadu State Board Solution Class 6 Science Term 2 Chapter 4 – Air.

Samacheer Kalvi 6th Science Term 2 Solutions Chapter 4: Overview


Samacheer Kalvi





Chapter Name


Samacheer Kalvi 6th Science Term 2 Solutions Chapter 4 Pdf

I.) Choose the correct answer.

1.) __________ is the percentage of Nitrogen in air.

a.) 78%

b.) 21%

c.) 0.03%

d.) 1%

Answer: 78%

Solution: The composition of air consist of 78% of nitrogen, 21% oxygen, 0.03% of Carbon-di-oxide and 1% of other gases.



2.) Gas exchange takes place in plants Using ___________.

a.) Stomata

b.) Chlorophyll

c.) Leaves

d.) Flowers

Answer: Stomata

Solution: Stomata are tiny pores on the leaves of plants that help in the exchange of gases in plants.



3.) The constituent of air that supports Combustion is __________.

a.) Nitrogen

b.) carbon-di-oxide

c.) Oxygen

d.) water vapour

Answer: Oxygen

Solution: In the presence of oxygen, combustion takes place. When a substance is burned in the presence of O2 , thereby releasing a large amount of light and heat , this process is called Combustion.



4.) Nitrogen is used in the food packaging Industry because it _________.

a.) Provides colour to the food

b.) Provides oxygen to the food

c.) Adds proteins and minerals to the Food

d.) Keeps the food fresh

Answer: Keeps the food fresh

Solution: Nitrogen is used to remove oxygen and moisture during packaging process , this helps in preserving or extending the quality of food for more days.


5.) _______ and ______ are the two Gases, which when taken together, Make up about 99 percentage of air.

 I.) Nitrogen

 II.) carbon-di-oxide

 III.) Noble gases

 IV.) Oxygen


a) I and II

b.) I and III

c.) II and IV

d.)  I and IV

Answer: I and IV

Solution: The percentage of Nitrogen and oxygen is 78% and 21% respectively in air. Together both constitute 99% of air.


II.) Fill in the blanks

1.)__Oxygen______ is the active component Of air.


2.) The gas given out during photosynthesis Is __Oxygen_____.


3.) ___Oxygen_______ gas is given to the patients Having breathing problems.


4.) _Tiny dust particles___ can be seen moving in a Beam of sunlight in a dark room.


5.) ___Carbon dioxide___ gas turns lime water milky.


III.) True or False. If False, give the Correct statement

1.) Inhaled air contains a large amount of Carbon-di-oxide.

Answer: False because a large amount of oxygen is present in inhaled air.


2.) Planting trees help in decreasing global Warming.

Answer: True


3.) The composition of air is always exactly The same.

Answer: False because the composition of air vary according to place and season.


4.) Whales come up to the water surface To breathe in oxygen.

Answer: True


5.) The balance of oxygen in atmosphere Is maintained through photosynthesis In animals and respiration in plants.

Answer: False, the balance of oxygen in atmosphere is maintained through photosynthesis In plants and Respiration in animals.


IV.) Match the following

i) Moving Air – Photosynthesis

ii) Layer in which we live – Troposphere

iii) Stratosphere –                                     Wind

iv) Oxygen – Ozone layer

v) Carbon-di-oxide – Combustion


Moving air Wind
Layer in which we live Troposphere
Stratosphere Ozone layer
Oxygen Combustion
Carbon-di-oxide Photosynthesis

 V.) Arrange the following statements In correct sequence

1.) Plants manufacture food by a process Called photosynthesis.

2.) Plants require energy for their growth.

3.) Plants take in oxygen and release Carbon-di-oxide just as animals.

4.) Plants take carbon-di-oxide from the Atmosphere, use chlorophyll in the Presence of sunlight and prepare food.

5.) Such oxygen is available to animals And human beings for breathing.

6.) During this process, oxygen is released By plants.


1.) Plants require energy for their growth.

2.) Plants manufacture food by a process called photosynthesis.

3.) During this process, oxygen is released by plants.

4.) Plants take in oxygen and release carbon-di-oxide just as animals.

5.) Such oxygen is available to animals and human beings for breathing.

6.) Plants take carbon-di-oxide from the atmosphere, use chlorophyll in the presence of sunlight and prepare food.

VI.) Analogy

1.) Photosynthesis : _____ :: Respiration : Oxygen

Answer: Carbon-di-oxide


2.) 78% of air : Does not support Combustion :: _____ : Supports Combustion

Answer: 21% of air

VII.) Observe the given figure Carefully and answer the Questions.

1.) What will happen if we remove plants From the aquarium?

Answer: If we remove plants From the aquarium then there will be a reduction in the amount of oxygen present underwater which is vital for the survival of aquatic organisms. There will be an increase in algae growth. Also the fishes will feel insecure without plants that provide them shelter.


2.) What will happen if we remove the fish From the aquarium and keep it (with Green plants) in a dark place?

Answer: If we remove the fish from the aquarium and keep it in a dark place with green plants then both the fish and plants will die.


VIII.) Give very short answer

1.) What is atmosphere? Name the five Layers of atmosphere.

Answer: Layers of gases surrounding our earth is called atmosphere. Five layers present in atmosphere are:

i) Troposphere

ii) Stratosphere

iii) Mesosphere

iv) Thermosphere

v) Exosphere


2.) How do the roots of land plants get Oxygen for breathing?

Answer: The air spaces in soil have an amount of oxygen present in them which is taken up by roots and later transferred to other parts of the plant.


3.) What should be done if the clothes of a Person catch fire accidentally? Why?

Answer: In such a situation, we need to fully cover the person using a rug or a blanket. This will help in minimising the flames of the fire, thereby completely cutting it off after sometime. A fire extinguisher can also be used in such a case.


4.) What will happen if you breathe Through mouth?

Answer: Snoring, dryness in mouth, feeling of tiredness during daytime and poor dental health are few health problems that can cause due to mouth breathing.


IX.) Give short answer

1.) Biscuits kept open on a plate during Monsoon days lose its’ crispness. Why?

Answer: The atmosphere during monsoon season contains water vapour. When biscuits are kept open, these vapours are absorbed by them and as a result biscuits lose their crispness.


2.) Why do traffic assistants wear a mask On duty?

Answer: Petrol and diesel, used in vehicles produce harmful gases and also emit a large amount of smoke and dust particles. So in order to protect themselves traffic assistants wear mask on duty.


X.) Answer in detail

1.) How do plants and animals maintain The balance of oxygen and carbon-di-Oxide in air?

Answer: Plants and animals maintain the balance of oxygen and carbon dioxide in the air by the processes of Respiration and photosynthesis.

In the process of Respiration, animals take in oxygen from their surroundings and exhale out Carbon-di-oxide. Plants also follow the same process at night. But during the day time, in the preparation of food, plants use Carbon-di-oxide along with water and Sunlight present in the nature to make their own food. Thus releasing oxygen during the process. This process by plant is called Photosynthesis.


2.) Why is atmosphere essential for life on Earth?

Answer: Atmosphere is essential for life on earth because:

  1. It consists of oxygen, Carbon-di-oxide, and other useful gases that are vital for the survival of living beings and plants.
  2. It helps in keeping the temperature moderate, thereby regulating the weather on earth.
  3. It has ozone layer that protects us from the harmful effects of UV rays.
  4. Water cycle present in nature is maintained by the presence of atmosphere.


XI.) Question based on Higher Order Thinking Skills

1.) Can you guess why fire extinguishers Throw a stream of carbon-di-oxide While putting – off fire?

Answer: Carbon-di-oxide is an odorless and colourless gas which doesn’t create byproducts while in contact with burning materials. It can be called an ideal fire suppressant, especially in places where there is high possibility that electricity may be present. As it doesn’t react with the burning material, it also doesn’t conduct Electricity. This is the reason why Carbon-di-oxide gas is used for putting off fire.

Updated: June 14, 2022 — 3:18 pm

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