Textbook Solution: Air Around Us | Living Science (Ratna Sagar) for Class 6 PDF Download

Oral Questions For Formative Assessment (P - 180)

Q1:
Ans: Thinner

Q2:
Ans: A mixture. It is a mixture of mainly nitrogen, oxygen, argon, carbon dioxide, and small amounts of other gases. Again varying quantities of dust, smoke, and water vapour are also present in the air.

Q3:
Ans: No, it varies in the air from place to place and from time to time.

Oral Questions For Formative Assessment (P -182)

Q1:
Ans: False, as for example, fishes breathe through gills.

Q2:
Ans: Yes, plants use oxygen for respiration during the day also. But the oxygen released during photosynthesis is more than the oxygen used up in respiration.

Q3:
Ans: The solubility of air in water reduces as the temperature increases.

Q4:
Ans: Yes, by the rotation of windmills

Q5:
Ans: Yes, the atmosphere absorbs some part of the sun's heat and reflects the rest. Again in the night, the trapped heat prevents the earth from cooling down too much.

For Formative and Summative Assessment (P - 183)

Q1:
Ans: d

Q2:
Ans: a

Q3:
Ans: d

Q4:
Ans: b

Q5:
Ans: c

Q6:
Ans: b

Q7:
Ans: c

Q8:
Ans: b

Part - B

Q1:
Ans: Atmosphere

Q2:
Ans: Nitrogen

Q3:
Ans: Nitrogen

Q4:
Ans: Respiration

Q5:
Ans: False

Q6:
Ans: Oxygen, carbon dioxide

Q7:
Ans: Gills

Q8:
Ans: Carbon dioxide

Q9:
Ans: Oxygen

Q10:
Ans: True

Q11:
Ans: Oxygen

Part - C

Q1:
Ans: The atmosphere is the blanket of air surrounding the earth.

Q2:
Ans: Carbon dioxide is considered to be so important because plants use carbon dioxide for preparing food which in turn gives food to the entire living world.

Q3:
Ans: The amount of water vapour in the air is known as humidity.

Q4:
Ans: Breathing is a necessary process in order to keep animals and humans alive. It allows animals and humans to take in oxygen. Whereas the energy required for the survival of organisms is produced through the process of respiration.

Q5:
Ans: Fish breathe through their gills.

Q6:
Ans: Yes, plants require nitrogen for their growth.

Q7:
Ans: The ozone layer prevents harmful rays of the sun from reaching the earth. These rays, called ultraviolet rays, can cause eye problems and skin cancer.

Part - D

Q1:
Ans: Air mainly contains nitrogen (78%) and oxygen (21%). The remaining 1% is made up of argon (about 0.9%), carbon dioxide (0.03%), and small amounts of other gases. Varying quantities of dust, smoke, and water vapour are also present in the air.

Q2:
Ans: Dust and smoke in the air are harmful to our respiratory system. Fine hair and mucus present in our nostrils filter them out and prevent them from getting into our respiratory system. That is why it is unhealthy to breathe through our mouth.

Q3:
Ans: Water lily leaves have stomata on the upper surface because the lower surface of the water lily is submerged and stomata are required for gas exchange in plants. So in water lilies, the stomata are located on the upper surface of leaves where it comes in contact with air.

Q4:
Ans: The natural cycle of consumption of oxygen by respiration and burning and its release by photosynthesis is called the oxygen cycle.

Q5:
Ans: Air is useful to us in many ways:
(i) It helps in breathing.
(ii) Wind helps to rotate the windmills and generate electricity.
(iii) It helps in the dispersal of seeds.
(iv) It helps the birds, insects, and bats to fly.

Q6:
Ans: The heat and light of the sun fall on the earth's atmosphere. Some of it is absorbed by the atmosphere, while the rest is reflected back. This prevents the earth from becoming very hot during the day. At night, the trapped heat in the atmosphere prevents the earth from cooling down too much. The atmosphere thus acts like a blanket around the earth and helps to keep the earth's surface at the right temperature for life to exist.

HOTS Questions

Q1:
Ans: Condensation of water droplets on the outside of a tumbler containing ice-cold water.

Q2:
Ans: (a) It is good to sleep under a tree during the day as the tree gives out oxygen.
(b) It is not good to sleep under a tree at night since the tree gives out carbon dioxide at night.

Q3:
Ans: Exposure to ultraviolet rays due to the depletion of the ozone layer in the region.

Q4:
Ans: Because the force of gravity becomes less as we go higher up. So this is unable to hold air.

Q5:
Ans: When the water got warm the solubility of air reduced. The air (including oxygen) dissolved in the water escaped. So all the fish died as they did not get oxygen in the water.