Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

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Tamilnadu Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Samacheer Kalvi 6th Science Air Textual Evaluation

I. Choose the appropriate answer:

Question 1.
_______ is the percentage of nitrogen in air
(a) 78%
(b) 21%
(c) 0.03%
(d) 1%
Answer:
(a) 78%

Question 2.
Gas exchange takes place in plants using …………
(a) Stomata
(b) Chlorophyll
(c) Leaves
(d) Flowers
Answer:
(a) Stomata

Question 3.
The constituent of air that supports combustion is _______
(a) Nitrogen
(b) carbon-di-oxide
(c) Oxygen
(d) water vapour
Answer:
(c) Oxygen

Question 4.
Nitrogen is used in the food packaging industry because of 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:
(d) keeps the food fresh

Question 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) I and II
(d) I and IV
Answer:
(d) I and IV

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

II. Fill in the blanks:

  1.  _______ is the active component of air.
  2. The gas given out during photosynthesis is _______
  3. _______ gas is given to the patients having breathing problems.
  4. _______ can be seen moving in a beam of sunlight in a dark room.
  5. _______ gas turns lime water milky.

Answers:

  1. Oxygen
  2. Oxygen
  3. Oxygen
  4. Dust particles
  5. Carbon-di-oxide

III. True or False. If False, give the correct statement:

Question 1.
Inhaled air contains a large amount of carbon-di-oxide.
Answer:
False, Inhaled air contains a large amount of Oxygen.

Question 2.
Planting trees help in decreasing global warming.
Answer:
True

Question 3.
The composition of air is always exactly the same.
Answer:
False, The composition of air changes slightly place to place.

Question 4.
Whales come up to the water surface to breathe in oxygen.
Answer:
True

Question 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:

Question 1.

1. Moving Air Photosynthesis
2. Layer in which we live Troposphere
3. Stratosphere Wind
4. Oxygen Ozone layer
5. carbon-di-oxide Combustion

Answer:

1. Moving Air Wind
2. Layer in which we live Troposphere
3. Stratosphere Ozone layer
4. Oxygen Combustion
5. carbon-di-oxide Photosynthesis

V. Arrange the following statements in the correct sequence.

Question 1.

  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.

Answers:

  1. Plants manufacture food by a process called photosynthesis.
  2. Plants require energy for their growth.
  3. Plants take in oxygen and release carbon dioxide just as animals.
  4. Plant take carbon dioxide 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.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

VI. Analogy:

Question 1.
Photosynthesis : _______ :: Respiration : Oxygen.
Answer:
Carbon – dioxide.

Question 2.
78% of air : Does not support combustion :: ________ : Supports combustion
Answer:
21% of air.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

VII. Observe the given figure carefully and answer the questions:

Question 1.
What will happen if we remove plants from the aquarium?
Answer:
If we remove the plants from the aquarium, the oxygen percentage will be decreased. So fishes would die.

Question 2.
What will happen if we remove the fish from the aquarium and keep it (with green plants) in a dark place?
Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 1
Answer:
If the aquarium is kept in a dark place, the green plants will not prepare their food due to lack of sunlight and carbon dioxide. So the plants get spoiled.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

VIII. Give a very short answer:

Question 1.
What is the atmosphere? Name the five layers of the atmosphere.
Answer:
Our earth is surrounded by a huge envelope of air called the atmosphere.
It is made up of five layers. They are:

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Ionosphere
  5. Exosphere

Question 2.
How do the roots of land plants get oxygen for breathing?
Answer:
The roots can absorb oxygen from the small air spaces in the soil.

Question 3.
What should be done if the clothes of a person catch fire accidentally? Why?
Answer:
If the clothes of a person catch fire accidentally, then immediately we should follow these three steps to put out the flames:

  1. “STOP” Don’t run. The fire victim must stop still. Ceasing any movement may fan the flames or hamper those attempting to put the fire out.
  2. “DROP” The fire victim must drop to the ground, lying down if possible, covering their face with their hands to avoid facial injury.
  3. “ROLL” The fire victim must roll on the ground in an effort to extinguish the fire by depriving it of oxygen.
  4. COOL off as soon as possible with water for first and second-degree bums.

Question 4.
What will happen if you breathe through your mouth?
Answer:
Anyone can develop a habit of breathing through their mouth, but certain conditions increase your risk. These include:-

  1. Chronic allergies
  2. Hay fever
  3. Chronic or recurring Sinus infections
  4. Asthma
  5. Chronic Stress and Anxiety.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

IX. Give a short answer:

Question 1.
Biscuits kept open on a plate during monsoon days lose their crispness. Why?
Answer:
Air also contains more water vapour in the rainy season (monsoon days). So, Biscuits kept open on a plate during monsoon days loses its crispness.

Question 2.
Why do traffic assistants wear a mask on duty?
Answer:
Traffic assistants are continually exposed to smoke coming from the vehicles. The smoke and the suspended particles in it if inhaled can cause breathing and lung problems. So traffic assistants wear masks.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

X. Answer in detail:

Question 1.
How do plants and animals maintain the balance of oxygen and carbon-di-oxide in the air?
Answer:
Respiration in plants:
During respiration, plants take in oxygen and release carbon-di-oxide, just as animals also do. Gaseous exchange with air in the atmosphere takes place in plants with stomata.

Photosynthesis:
During photosynthesis, carbon-di-oxide from the air and water from the soil react in the presence of sunlight to produce food. Plants release oxygen during photosynthesis which is much more than the oxygen consumed by the plants during respiration.

Respiration in animats:
When we breathe in air, the oxygen present in the air reacts chemically with digested food within the body to produce carbon-di-oxide gas. The inhaled air contains more oxygen while the exhaled air contains more carbon-di-oxide.

So plants sent out more oxygen during photosynthesis. Animals sent out more carbon-di-oxide during respiration. Plants take carbon-di-oxide for photosynthesis. Animals take oxygen during respiration. So plants and animals maintain the balance of oxygen and carbon-di-oxide in the air.

Question 2.
Why is the atmosphere essential for life on earth?
Answer:
Our earth is surrounded by a huge envelope of air called the atmosphere.

The atmosphere extends to more than 800 km above the surface of the earth and is held in place by the earth’s gravity. The atmosphere protects us from many harmful rays coming from the sun. The air envelope is thicker near the earth’s surface and as we go higher the density and the availability of air gradually decreases. This is because, as we go higher, the force of gravity decreases, so it is not able to hold a large amount of air.

The atmosphere is made of five different layers – the troposphere, the stratosphere, the mesosphere, the ionosphere and the exosphere.

The troposphere is the layer closest to the earth. It is the layer in which we live. It extends upwards for about 16 km above the surface of the earth. The movement of wind takes place in this layer. It also contains water vapour, which is responsible for making clouds. This layer is responsible for the weather we experience on earth.

Air crafts usually fly above this layer to avoid strong winds and bad weather.

The stratosphere lies above the troposphere. This layer has the ozone layer in it. The ozone layer protects all life on earth from the harmful ultraviolet rays of the sun.

The atmosphere contains a large amount of air. Air is used by plants and animals for breathing. It is used for burning fuels like wood, coal, kerosene. LPG etc. Air plays an important role in maintaining the water cycle in nature. So the atmosphere is essential for life on earth.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

XI. Questions Based on Higher Order Thinking Skills:

Question 1.
Can you guess why fire extinguishers throw a stream of carbon-di-oxide while putting – off the fire?
Answer:
The reasons behind fire extinguishers throw a stream of CO, while putting-off fire:-

  1. CO2 is a colourless and in normal concentrations, odourless gas. It doesn’t react with burning materials, so it doesn’t create any toxic or other by-products while putting-off fire.
  2. Carbon dioxide doesn’t conduct electricity, making it an ideal fire suppressant for use in places where a large amount of electricity may be present.
  3. CO2 acts on fires in two ways: The release of the gas under pressure has a cooling effect, as can be seen by the resulting mist cloud and ice particles; the gas also displaces the oxygen that’s necessary to maintain combustion.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Samacheer Kalvi 6th Science Air Intext Activities

Activity 1

Air is everywhere
Let us take an empty glass bottle. Is it really empty or does it have something inside?
Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 2
Now, shall we turn the glass bottle upside down? Can you agree that there is still something inside the empty glass bottle? Let us do the following activity to find what is there inside an empty glass bottle.
Dip the open mouth of the bottle into the trough filled with water as shown in Fig 1.
Observe the bottle. Does water enter the bottle? _______
Now tilt the bottle slightly. Now again dip the open mouth of the bottle as shown in Fig 2.
Do you think that water will enter the bottle? _______
Kindly observe Fig 2 carefully. You can see bubbles coming out of the bottle.
When you perform the experiment, can you hear the bubbly sound? can you now guess what was inside the bottle? _______
Yes, you are right. It is “air” that was present in the bottle.
The bottle was not empty at all. In fact, it was filled completely with air even when you turned it upside down. That is why we notice that water does not enter the bottle when it is pushed in an inverted position, as there was no space for air to escape.
When the bottle was tilted, the air was able to come out in the form of bubbles and water-filled up the empty space that the air has occupied.
Hence we can see that air fills all the space inside the bottle.
Answer:
Fig. – 1 – No.
Fig – 2 – Yes.
Yes, I can hear a bubbly sound. Yes, the bottle has full of ‘Air’.

Activity 2

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 3
Take a healthy branch of Hydrilla and place it in a funnel. Invert the funnel in a beaker of water as shown in the figure. Invert a test tube over the stem of the funnel. The stem of the funnel should be kept immersed inside the water Leave the beaker in sunlight for some time. You will notice some bubbles rising in the test tube. The bubbles contain oxygen released by the plant during photosynthesis. If we show a glowing splinter to the collected air, it burns brightly. This shows that the collected gas is oxygen.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Activity 3

We know that iron undergoes rusting with oxygen and forms iron oxide. This process can be used to estimate the percentage of oxygen in the air, which has been removed by the rusting reaction.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 4

Take a small portion of iron wool, press it into a 20 ml graduated test tube and wet it with water. Tip away excess of water. Take a 500ml beaker and fill half of the beaker with water. Invert the test tube and place it in air. Leave the arrangement at least for a week without making any disturbance to the test tube.

Observe the changes that had happened in the iron wool and to the level of water inside the test tube. We could see that the water level has increased inside the test tube. The rise in water is because of oxygen in air which has been removed by the rusting reaction. This will be about 20% which is approximately the percentage of oxygen in the air.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Activity 4

Oxygen is necessary for burning

Place two candles on a table. Ensure that both the candles are of the same size and height. Mark them as candle 1 and candle 2 using a chalk piece. Light both the candles. Now, cover candle 2 with a glass tumbler as shown in the figure. Observe the happenings at both the candles.

What does happen to candle 1?
_________________________
What does happen to candle 2?
_________________________
Can you guess why did the covered candle extinguish?
_________________________

Let us summarize the happenings.

Candle 1 continues to bum unless it is blown – off by strong moving air or any other external force. This is because fresh air is continuously available to the candle for its burning process.

Candle 2 glows for a while and then gets put – off. When the burning candle is covered with a glass tumbler, the candle can use the oxygen available in the air inside the glass tumbler. Since only a small amount of air is present inside the glass tumbler – only a small portion of the oxygen is available for the candle to continue glowing. When all the oxygen of the air inside the gas jar is used up, then the burning candle gets extinguished.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 5

Now, repeat the candle – glowing experiment taking four containers of different sizes. Lor example, you can take a 250ml conical flask, a 500ml bottle, a one-liter jar, a two-liter jar. Cover the burning candle one by one with these containers and find out how long it takes for the candle to extinguish in each case. Record your observations in the following table.
Answer:

S.No.

The volume of the container (ml)

Time is taken for the candle to extinguish (second)

1. 250 6 seconds
2. 500 12 seconds
3. 1000 24 seconds
4. 2000 48 seconds

The time taken for the candle to extinguish depends upon the volume of the containers. Lor less volume, the time taken is less. Lor more volume, the time taken is more.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Samacheer Kalvi 6th Science Additional Questions

I. Choose the correct answer:

Question 1.
Movement of wind takes place in _______ layer
(a) Troposphere
(b) ozone
(c) stratosphere
(d) ionosphere
Answer:
(a) Troposphere

Question 2.
A component of air used by green plants to prepare their food is
(a) N2
(b) O2
(c) He
(d) CO2
Answer:
(d) CO2

Question 3.
_______ layer contain ozone layer.
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
(d) Exosphere
Answer:
(b) Stratosphere

Question 4.
The percentage of oxygen in the exhaled air of respiration is
(a) 78%
(b) 16%
(c) 4%
(d) 21%
Answer:
(b) 16%

Question 5.
During respiration, carbon-di-oxide is exhaled out of the body through the _______
(a) Lungs
(b) Heart
(c) Kidney
(d) Skin
Answer:
(a) Lungs

Question 6.
_______ respire using their skin.
(a) Fish
(b) Frogs
(c) Rats
(d) Human beings
Ans:
(b)Frogs

Question 7.
_______ gas cylinders are used for breathing purpose for a diver going deep into the sea
(a) Hydrogen
(b) Carbon-di-oxide
(c) Oxygen
(d) Nitrogen
Answer:
(c) Oxygen

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

II. Fill in the blanks:

  1. The atmosphere is held in place by the earth’s _______
  2. The atmosphere is made of _______ different layers.
  3. A _______ shows the direction in which the air is moving at a particular place.
  4. The ozone layer protects all life on earth from the harmful _______ rays of the sun.
  5. Highly reactive gas was later names ‘oxygen’ by _______
  6. _______ discovered nitrogen.
  7. Air contains a small amount of CO2, Water vapour and some other gases like _______ etc.
  8. Air contains more _______ in rainy season

Answers:

  1. gravity
  2. five
  3. weathercock
  4. ultraviolet
  5. Lavoisier
  6. Daniel Rutherford
  7. argon, helium
  8. water vapour

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

III. Find whether the following sentences are true or false. If false Correct the statement:

Question 1.
When air is moving with cool and soothing, it is called a cyclone.
Answer:
False. When air is moving with cool and soothing is called a breeze.

Question 2.
Exosphere has a high temperature.
Answer:
False. Exosphere has a low temperature.

Question 3.
Jan Ingenhousz showed that chlorophyll is essential to the plant to carry out photosynthesis.
Answer:
False. Jan Ingenhousz showed that sunlight is essential to the plant to carry out photosynthesis.

Question 4.
The second major component of air is oxygen.
Answer:
True.

Question 5.
Air also contains a small amount of carbon-di-oxide, water vapour, and some other gases like argon, helium, etc.
Answer:
True.

Question 6.
The amount of water vapour in the air is more in windy places than in other areas.
Answer:
False. The amount of dust in the air is more in windy places than in other areas.

IV. Match the following:

1. More industrial cities (a) dust particles
2. Coastal areas b) Humidity
3. Rainy season c) Carbon dioxide
4. Windy places (d) water vapour

Answer:

  1. – c
  2. – d
  3. – b
  4. – a

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

V. Analogy:

Question 1.
Cool and soothing wind : Breeze.
uproot trees wind : ________
Answer:
Cyclone

Question 2.
Weather changes : Trophosphere.
Ozone layer: ________
Answer:
Stratosphere

Question 3.
Oxygen : Joseph Priestley.
Nitrogen : ________
Answer:
Daniel Rutherford

Question 4.
Respire through skin: ________
Respire through gills: Fish
Answer:
Frogs

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

VI. Give Short Answer:

Question 1.
Define – Atmosphere.
Answer:
Our earth is surrounded by a huge envelope of air. It is called the atmosphere.

Question 2.
The air envelope is thicker near the earth’s surface and we go higher the density and availability of air gradually decreases. Why?
Answer:
When altitude increases, a number of gas molecules will be decreased. Therefore, the density is also decreased when we go higher. Gravity pulls most of the atmosphere’s gas molecules close to the Earth’s surface. Air rises as it is heated because it becomes less dense.

Question 3.
Define troposphere.
Answer:

  1. This layer is closest to the earth.
  2. It is the layer in which we live.
  3. The movement of wind takes place in this layer.
  4. It also contains water vapour, which is responsible for making clouds.
  5. It is responsible for the weather we experience on earth.

Question 4.
Why aircraft usually fly above the troposphere layer?
Answer:
Aircraft usually fly above the troposphere to avoid strong winds and bad weather.

Question 5.
How to show that the presence of carbon-di-oxide in the air?
Answer:
Pour some lime water in a glass tumbler Bubble some air using a straw through the liter water. After a few minutes, lime water will produce a white precipitate and that the lime water will turn to a milky white solution. This shows the presence of Carbon- dioxide in air.

Question 6.
Write the composition of air.
Answer:
The major component of air is nitrogen. Almost four-fifth of air is nitrogen. The second major component of air is oxygen. Air also contains a small amount of Carbon-dioxide, water vapour, and some other gases like argon, helium, etc. The air may also contain some dust particles.

Question 7.
The composition of air changes slightly from place to place. Give examples.
Answer:

  1. The air over industrial cities has a higher amount of carbon-di-oxide in it.
  2. The air in coastal areas may have more water vapour than inland areas.
  3. Air also contains more water vapour in the rainy season.
  4. The amount of dust in the air is more in windy places.

Question 8.
What is meant by burning?
Answer:
The process of burning a substance in the presence of oxygen and releasing a large amount of light and heat is called burning.

Question 9.
In Rockets, along with fuel, oxygen is also carried for combustion – why?
Answer:
In Rockets, as they go high in the atmosphere, the availability of oxygen is considerably reduced. So rockets along with the fuel, oxygen is also carried for combustion.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Question 10.
Write the equation of photosynthesis.
Answer:
Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 6

Question 11.
What is dry ice? What is its use?
Answer:

  1. When carbon-di-oxide is cooled to -57°C, it directly becomes a solid, without changing to its liquid state. It is called dry ice.
  2. Dry ice is used in trucks or freight cars for refrigerating meat and fish while transporting them.

Question 12.
Write the uses of windmills.
Answer:
The windmills are used

  1. to draw water by running pumps
  2. run flour mills
  3. to generate electricity.

Question 13.
Give the components present in the air with a percentage?
Answer:
The components present in the air with percentage Nitrogen – 78%, Oxygen – 21%, Carbon di oxide, Argon, Water vapour, and other gases – 1%.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

VII. Answer in detail:

Question 1.
Prove by an experiment that Oxygen is released during photosynthesis.
Answer:

  1. Take a healthy branch of Hydrilla and place it in a funnel. Invert the funnel in a beaker of water as shown in the figure.
  2. Invert a test tube over the stem of the funnel.
  3. The stem of the funnel should be kept immersed inside the water Leave the beaker in sunlight for some time.
  4. You will notice some bubbles rising in the test tube.
    Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 7
  5. The bubbles contain oxygen released by the plant during photosynthesis.
  6. If we show a glowing splinter to the collected air, it bums brightly.
  7. This shows that the collected gas is oxygen.

Question 2.
Prove by an experiment that oxygen is necessary for burning.
Answer:

  1. Place two candles on a table.
  2. Ensure that both the candles are of the same size and height.
  3. Mark them as candle 1 and candle 2 using a chalk piece.
  4. Light both the candles. Now, cover candle 2 with a glass tumbler as shown in the figure.
  5. Observe the happenings at both the candle.
    Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air 8
  6. Candle 1 continues to burn unless it is blown – off by strong moving air or any other external force.
  7. This is because fresh air is continuously available to the candle for its burning process.
  8. Candle 2 glows for a while and then gets put – off.
  9. When the burning candle is covered with a glass tumbler, the candle can use the oxygen available in the air inside the glass tumbler.
  10. Since only a small amount of air is present inside the glass tumbler – only a small portion of the oxygen is available for the candle to continue glowing.
  11. When all the oxygen of the air inside the gas jar is used up, then the burning candle gets extinguished.

Samacheer Kalvi 6th Science Solutions Term 2 Chapter 4 Air

Question 3.
Compare the composition of inhaled air and exhaled air.
Answer:

Component Inhaled air Exhaled air
Nitrogen 78% 78%
Oxygen 21% 16%
Carbon-di -oxide 0.03% 4%
Water vapour Variable amount amount increases in exhaled air
Noble gases 0.95% 0.95%
Dust Variable amount none
Temperature Room temperature Body temperature

Question 4.
Write the uses of air.
Answer:

  1. Air is used by plants and animals for breathing.
  2. Air is used for burning fuels like wood, coal, kerosene, LPG, etc.
  3. Compressed air is used to fill tyres of various kinds of vehicles.
  4. The ozone layer, present in the atmosphere, helps in preventing harmful radiations of the sun from reaching the earth’s surface.
  5. Under extraordinary conditions such as:
    • a patient having breathing difficulties,
    • a mountaineer climbing a high mountain,
    • a diver going deep into the sea, oxygen gas cylinders are used for breathing purposes.
  6. Blowing air is used to turn the blades of windmills. The windmills are used to draw water by running pumps, run flour mills, and to generate electricity.

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