Living Science 2019 Solutions for Class 6 Science Chapter 16 Air Around Us are provided here with simple step-by-step explanations. These solutions for Air Around Us are extremely popular among Class 6 students for Science Air Around Us Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science 2019 Book of Class 6 Science Chapter 16 are provided here for you for free. You will also love the ad-free experience on Meritnationâ€™s Living Science 2019 Solutions. All Living Science 2019 Solutions for class Class 6 Science are prepared by experts and are 100% accurate.

#### Question 1:

Does the density of the blanket of air that surrounds us get thicker or thinner as we go up?

The density of the blanket of air that surrounds us becomes thinner as we go up.

#### Question 2:

Air is a mixture and not a compound. This is because air consists of indefinite composition of different gases and this composition can vary from place to place. Moreover, the different gases present in air show their individual properties which suggests that air is not a compound.

#### Question 3:

The percentage of water vapour in the air is always the same. Do you agree? Give reasons.

No, the percentage of water vapours in the air is not always same. The percentage of water vapour varies from time to time and from place to place. The amount of water vapour present in the air depends on a number of factors such as temperature and temperature changes from one place to another. This results in variable composition of water vapour in the air.

#### Question 1:

All animals breathe in oxygen through lungs. True or False? Justify your answer.

The given statement is false. This is because animals such as fishes use gills to obtain oxygen from the water. Moreover, some animals such as earthworms can even breathe through their skin. Thus, all animals do not breathe through lungs.

#### Question 2:

Plants take in carbon dioxide for photosynthesis during the day. Do they also use oxygen during the day? Justify your answer.

Yes, plants use oxygen during the day. This is because the plants require oxygen for performing respiration so that they can obtain energy. Like all living organisms, plants also require constant supply of energy and thus, they use oxygen during the day.

#### Question 3:

How does the solubility of air in water change as the temperature increases?

The solubility of air in water decreases with an increase in the temperature.

#### Question 4:

Can air be used to generate electricity? How?

Air can be used to generate electricity through windmills. The winds generated from the air can be used to rotate the blades of the windmills. The rotation of these blades generates electricity through a dynamo.

#### Question 5:

Without the atmosphere, the earth would have been very hot during the day and very cold at night. Do you agree? Give reasons.

Yes, the Earth would have been incredibly cold at the night and extremely hot during the day if the atmosphere was not present. The light and heat emitted by the Sun is absorbed by the atmosphere and some part of it is reflected back. This helps to keep the day temperature to an optimum value. During night, the heat trapped by the atmosphere helps the keep the temperature warm which prevents excessive lowering of temperature. Thus, in the absence of atmosphere, temperature of Earth will be very hot during the day and extremely cold during the night.

#### Question 1:

The presence of which of these components in air varies from place to place?
(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) water vapour

(d) water vapour
The presence of water vapour in air varies from place to place.

#### Question 2:

Which of these is not true for combustion?
(a) Oxygen is formed.
(b) Carbon dioxide is formed.
(c) Oxygen is used up.
(d) Nitrogen does not change.

(a) Oxygen is formed.
During combustion, oxygen is used, giving out carbon dioxide.

#### Question 3:

Which of these is not an organ for taking in oxygen?
(a) lungs
(b) gills
(c) stomata
(d) atmosphere

(d) Atmosphere
Atmosphere is the layer of air surrounding the earth which contains oxygen.

#### Question 4:

Which of the following gases protects us from ultraviolet rays?
(a) oxygen
(b) ozone
(c) carbon dioxide
(d) nitrogen

(b) Ozone
Ozone layer is a layer of gases present in the atmosphere that protects the Earth from the ultraviolet rays of the sun.

#### Question 5:

The percentage of oxygen in the air does not change because
(a) oxygen is not used in any natural process.
(b) oxygen used up in natural processes is negligible.
(c) oxygen used up in some natural processes is renewed by another natural process.
(d) oxygen used up in natural processes is replenished by the ozone layer.

(c) Oxygen used up in some natural processes is renewed by another natural process.
The percentage of oxygen in the air does not change because the oxygen used in respiration and combustion is replaced by the oxygen generated by plants during photosynthesis.

#### Question 6:

Which of these can plants not absorb directly form the atmosphere?
(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) all of these

(b) Nitrogen.
Though plants require nitrogen for their growth, plants cannot absorb nitrogen directly from the atmosphere.

#### Question 7:

Which of these plants does not have stomata?
(a) water lily
(b) lotus
(c) tape grass
(d) all of these

(c) Tape grass.
Stomata are absent in tape grass. Their body absorb the dissolved oxygen from water.

#### Question 8:

The percentage amount of which of these gases in air is the least?
(a) oxygen
(b) carbon dioxide
(c) nitrogen
(d) cannot say because it varies from place to place

(b) Carbon dioxide.
The percentage amount of carbon dioxide in air is the least, i.e., 0.03%.

#### Question 9:

The air in which of these is expected to be most polluted?
a. A high mountain peak
b. A wild life sanctuary
c. A farmland
d. An industrial town

d. An industrial town

An industrial town is expected to have highest amount of pollution because of the presence of large number of industries.

#### Question 1:

The blanket of air surrounding the earth is called the _______________

The blanket of air surrounding the earth is called the atmosphere.

#### Question 2:

The major component of air is ___________

The major component of air is nitrogen.

#### Question 3:

Plants need the gas __________, but they cannot take it directly from the atmosphere.

Plants need the gas nitrogen, but they cannot take it directly from the atmosphere.

#### Question 4:

Bodies of living things release energy during the process of _________

Bodies of living things release energy during the process of respiration.

#### Question 5:

Respiration and combustion remove carbon dioxide from the air. True or false?

False.
During respiration and combustion oxygen in the air is used up leaving behind carbon dioxide.

#### Question 6:

Plants release the gas ___________ during the day and the gas ___________ at night.

Plants release the gas oxygen during the day and the gas carbon dioxide at night.

#### Question 7:

Plants respire only at night. True or false?

False.
Like other living beings, plants also respire constantly irrespective of day and night. However, during day they also give out oxygen by photosynthesis than what they use for respiration.

#### Question 8:

The percentage of ______________ present in air is 0.03% by volume.

The percentage of carbon dioxide present in air is 0.03% by volume.

#### Question 9:

Name the organ used by fishes to breathe in air dissolved in water.

Gills present in fish helps them to breathe in air dissolved in water.

#### Question 10:

The atmosphere is responsible for weather changes. True or false?

True. The changes in the weather occurs due to the atmosphere surrounding the earth.

#### Question 11:

The __________ cycle gets disturbed by deforestation.

The oxygen cycle gets disturbed by deforestation.

#### Question 1:

What do you mean by 'atmosphere'?

Atmosphere is a layer or blanket of air surrounding the earth. It extends up to 1000 kilometres above the earth's surface.

#### Question 2:

Carbon dioxide is present to the extent of only 0.03% by volume in air. Why then is it considered to be so important?

Though carbon dioxide is present in lesser amount, it is very essential for both plants and animals. Plants require carbon dioxide to prepare their food. All animals in turn depend upon plants either directly or indirectly for their nutrition.

#### Question 3:

What is humidity?

The amount of water vapours present in the air is called as humidity.

#### Question 4:

What is the difference between breathing in and respiration?

 Breathing in Respiration Breathing in is inhaling air. Respiration is the process which involves breathing in and breathing out. It involves the diaphragm, lungs, nose, wind passages and the chest Respiration happens in every cell. Breathing in is simply a physical process of taking in air. Respiration is a chemical process where the oxygen in air reacts with digested food to give energy.

#### Question 5:

How do fish breathe?

Fish have gills, with the help of which they breathe in the oxygen present in water. The water containing the dissolved oxygen passes through the gills and the oxygen gets absorbed by the gills.

#### Question 6:

Do plants require nitrogen? Why?

Yes, plants require nitrogen because it is involved in the growth of the plant.

#### Question 7:

What is the importance of the ozone layer in the atmosphere?

Ozone layer is a protective layer of gases which is present in the upper atmosphere. This layer blocks harmful ultraviolet rays from the sun and prevents them from reaching the earth.

#### Question 8:

When is air said to be polluted?

Air is said to be polluted when the composition of different gases in the air is dramatically altered. Moreover, addition of gases that are not normally found in the air also leads to air pollution.

#### Question 1:

What is the composition of air.

Air is a combination of different gases. The major components of air are as follows:
(a) Nitrogen - 78%
(b) Oxygen - 21%
(c) The remaining 1% consists of argon (about 0.9%), carbon dioxide (about 0.03%) and traces of other gases.
(d) It also consists of water vapour, dust and smoke which varies timely from place to place.

#### Question 2:

Why is it considered unhealthy to breathe in through the mouth?

If we breathe in through the mouth, the smoke and dust particles present in the air, enters directly into our respiratory system which is harmful and cause damage to our respiratory system. Hence, to avoid this, we must breathe through our nose, where these particles are filtered by the fine hairs and mucus present in nostrils.

#### Question 3:

Most plants have stomata on the undersides of leaves. However, water lily leaves have stomata on the upper surface. Why?

Stomata are the small openings present underneath the leaves of the plants with the help of which plants breathe in air. In water lilies, the leaves float on the surface of the water. In such condition, if the stomata are present underneath, it would be difficult for them to breathe in oxygen. Hence, in water plants stomata are present on the upper surface.

#### Question 4:

What is the oxygen cycle?

Oxygen cycle is the movement of oxygen from the atmosphere to earth and vice versa. Plants and animals use oxygen present in the air for respiration. Oxygen is also used for combustion. This oxygen is replaced by the plants during photosynthesis. This cycle repeats balancing the volume of oxygen in the air.

#### Question 5:

List any four uses of air.

Following are the uses of air:
(i) It helps in restoring the water balance in nature.
(ii) It is used to generate electricity, with the help of wind mills.
(iii) It helps in seed dispersal for pollination.
(iv) It makes the flight of airplanes and helicopters possible.

#### Question 6:

How does the atmosphere help to maintain the right temperature on the earth?

Sun emits heat and light, a part of which is absorbed by the atmosphere and the rest of it is reflected back. This prevents the earth from getting too hot during the day time. Similarly, during the night time, the trapped heat in the atmosphere prevents the earth from getting too cold. In this way the atmosphere help to maintain the right temperature on the earth.

#### Question 7:

List three steps we can take in our daily lives to reduce air pollution.

The steps that should be taken to reduce air pollution are as follows:
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1. We should try to use public transport instead of personal transportation.

2. More efficient fuels such as compressed natural gas (CNG) should be used because they produce less smoke.

3. We should try to plant trees so that the extent of air pollution is reduced.

#### Question 1:

Can you think of one observation in your daily life which shows the presence of water vapour in the air?

Rusting of iron is a best example to show the presence of water vapour in the air. When the iron interacts with the air, the water vapour present in the air undergo chemical reaction with the iron forming a reddish brown substance on the surface of the iron which is called as rust.

#### Question 2:

Is it good to sleep under a tree
(a) during the day,
(b) at night? Give reasons.

During the day time the leaves of the trees give off a plenty of oxygen in the process of photosynthesis. The amount of oxygen given off far exceeds the amount of carbon dioxide given out by the process of the tree respiring.
At night, there is no sunlight and photosynthesis stops. The trees however, continue to respire. As a result, trees give out carbon dioxide at night. Therefore, it is not advisable to sleep under a tree at night.

#### Question 3:

People living in a certain region have a high incidence of skin cancer. Can you identify one possible cause for this?

This may be due to the damage of ozone layer in that particular region. The sun emits ultraviolet radiation which can cause skin cancer. The ozone layer, present in the upper atmosphere, acts as a shield and protects the earth from these rays. If the ozone layer is damaged, then a large amount of ultraviolet radiation falls on the earth and can cause skin cancer if people are exposed to the ultraviolet radiation.

#### Question 4:

Why do you think air becomes thinner higher up? (HINT: think of which force holds the atmosphere to the earth)

The gravitational force which attract every object towards the surface of the earth, also attracts the air, which makes the air denser on the surface of the earth. As the air moves up, i.e., away from the surface of the earth, the lesser gravitational force causes the air to be less dense or thinner.

#### Question 5:

An aquarium owner, on a rather cold day, put a heater in his aquarium, which made the water warm, but not hot. He thought the fish would like that. However, all his fish died. What could be the reason for this?

Air heats up and cools down faster than water. Even when the air is cool, the water is relatively warm. Since, changes in water temperature are never as severe as changes in the temperature of air, aquatic animals such as fish are very sensitive to small changes in temperature.When a heater is put into the water, it was not as cold as the air to begin with. The increase in the warmth of the water coupled with the high temperature sensitivity of aquatic animals led to the death of the fishes in the aquarium.

#### Question 1:

Four burning candles are covered as shown. Arrange them in decreasing order of the time for which they will continue to burn.