Lesson.4 Air
Lesson.4 Air
I. Choose the correct answer:
1. __________ is the percentage of nitrogen in air.
- 78%
- 21%
- 0.03%
- 1%
Ans : 78%
2. Gas exchange takes place in plants using ___________.
- Stomata
- Chlorophyll
- Leaves
- Flower
Ans : Flower
3. The constituent of air that supports combustion is __________.
- Nitrogen
- carbon-di-oxide
- Oxygen
- water vapour
Ans : Oxygen
4. Nitrogen is used in the food packaging industry because it _________.
- provides colour to the food
- provides oxygen to the food
- adds proteins and minerals to the food
- keeps the food fresh
Ans : keeps the food fresh
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 |
- I and II
- I and III
- II and IV
- I and IV
Ans : I and IV
II. Fill in the blanks
1. __________ is the active component of air
Ans : Oxygen
2. The gas given out during photosynthesis is _________.
Ans : Oxygen
3. __________ gas is given to the patients having breathing problems.
Ans : Oxygen
4. _______ can be seen moving in a beam of sunlight in a dark room.
Ans : Dust particles
5. ________ gas turns lime water milky.
Ans : Carbon-di-oxide
III. True or False. If False, give the correct statement
1. Inhaled air contains a large amount of carbon-di-oxide.
Ans : False
Cu. An : Inhaled air contains a less amount of carbon-di-oxide
2. Planting trees help in decreasing global warming.
Ans : True
3. The composition of air is always exactly the same
Ans : False
Cu. An : The composition of air is always exactly not the same.
4. Whales come up to the water surface to breathe in oxygen.
Ans : True
5. The balance of oxygen in atmosphere is maintained through photosynthesis in animals and respiration in plants.
Ans : False
Cu. An : The balance of oxygen in atmosphere is maintained through respiration in animals and photosynthesis in plants.
IV. Match the Following
| 1. Moving Air | Photosynthesis | |
| 2. Layer in which we live | Troposphere | |
| 3. Stratosphere | Wind | |
| 4. Oxygen | Ozone layer | |
| 5. carbon-di-oxide | Combustion | |
| Ans : 1 – D, 2 – E, 3 – A, 4 – C, 5 – B | ||
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.
Ans :
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.
1. Plants manufacture food by a process called photosynthesis.
6. During this process, oxygen is released by plants.
5. Such oxygen is available to animals and human beings for breathing.
VI. Analogy
1. Photosynthesis : _____ :: Respiration : Oxygen
Ans : carbon-di-oxide
2. 78% of air : Does not support combustion :: _____ : Supports combustion
Ans : 21%
VII. Observe the given figure carefully and answer the questions.
1. What will happen if we remove plants from the aquarium?
Remove plants it Reduced Oxygen level from aquarium.
2. What will happen if we remove the fish from the aquarium and keep it (with green plants) in a dark place?
photosynthesis not possible,if remove fish from aquarium it will dead.
VIII. Give very short answer
1. What is atmosphere? Name the five layers of atmosphere.
Our earth is surrounded by a huge envelope of air called the atmosphere.The troposphere, The stratosphere, The mesosphere, The ionosphere and The exosphere .
2. How do the roots of land plants get oxygen for breathing?
They can absorb oxygen from small air spaces in soil.
3. What should be done if the clothes of a person catch fire accidentally? Why?
Drop to the floor roll slowly on the floor or ground.
4. What will happen if you breathe through mouth?
Mouth breathing can help get oxygen to muscles faster.
IX. Give short answer
1. Biscuits kept open on a plate during monsoon days lose its’ crispness. Why?
Biscuits can obsorb moisture from air so it lost its crispness.
2. Why do traffic assistants wear a mask on duty?
To avoid inhaled suspended particles from air.
X. Answer in detail
1. How do plants and animals maintain the balance of oxygen and carbon-dioxide in air?
- Plants require energy for their growth and hence respiration also occurs in plants.
- During respiration, plants take in oxygen and release carbon–di–oxide, When we breathe in air, the oxygen present in the air reacts chemically with digested food within the body to produce carbon-di-oxide.
- Thus plants and animals maintain the balance of oxygen and carbon- di-oxide in air
2. Why is atmosphere essential for life on earth?
- Our earth is surrounded by a huge envelope of air called the atmosphere. Atmosphere extends to more than 800km above the surface of 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 large amount of air.
- The atmosphere is made of five different layers – the troposphere, the stratosphere, the mesosphere, the ionosphere and the exosphere.
- 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.