Chhattisgarh Board Class 8 Science Chapter 3 Solution

Last updated on February 6th, 2024 at 12:53 am

CG Board Class 8 Science Air

 

Chhattisgarh Board Class 8 Science Chapter 3 Solution Textbook question and answers as well as extra question and answers from the chapter

 

Choose the correct alternative-

1. Which gas has the highest percentage in air?

a) Oxygen b) Nitrogen c) Helium d) Carbon dioxide

 

2. Nitrogen is used in the storage of food items because

1. it provides oxygen to the food items
2. it provides carbon-dioxide to the food items
3. it provides protein to the food items
4. it keeps the food fresh.

 

3. Unit measure of atmospheric pressure is equal to the column of mercury pressure of –

a) 76 cm b) 76 mm c) 1.013 mm d) 10.13 mm

 

4. Oxygen gas as compared to water is –

a) heavier b) lighter c) equal d) none of these

 

5. The cause of heating up of our atmosphere is

a) Ozone layer b) greenhouse effect c) nitrogen d) oxygen

 

Fill in the blanks

1. ………………………..gas helps in burning.[oxygen]
2. Of a nitrogen rich fertilizer ………………………..is the main source.[ammonia]
3. The atmospheric pressure ………………………..on going upwards from the earth surface.[decreases]
4. Acid rain is due to ………………………..and ………………………..gases. [sulphur di-oxide and nitrogen oxide]
5. Oxygen is ………………………..in water. [less soluble]

 

Find the correct sentences from these and rewrite the wrong sentences correctly.

1. The percentage of oxygen in air is 10 percent.
2. On heating potassium permanganate we get nitrogen gas.
3. Sulphur dioxide when mixed with air, pollutes it.
4. The air pressure in the balloon is due to the air filled in it, striking the walls of the balloon.
5. Because of the inertness of nitrogen gas, it is filled in the electric bulbs.

 

Corrected sentences:

1. The percentage of oxygen in air is 21 percent.
2. On heating potassium permanganate we get oxygen gas.
3. Sulphur dioxide, when mixed with air, pollutes it.
4. The air pressure in the balloon is due to the air filled in it, exerting force on the walls of the balloon.
5. Because of the inertness of nitrogen gas, it is filled in the electric bulbs to prevent oxidation of the filament.

 

Answer the following questions.

 

Q- What are the components of air?

The main components of air are approximately:

• Nitrogen (N2): 78%
• Oxygen (O2): 21%
• Argon (Ar): 0.9%
• Water vapor (H2O): 0.04%
• Carbon dioxide (CO2): 0.03%
• Other gases and dust particles.

 

Q- What are the causes of air pollution? What measures would you adopt to stop it?

Causes of air pollution and measures to stop it:

Causes:

• Vehicle emissions (carbon monoxide, oxides of nitrogen)
• Industrial activities (particulate matter, sulfur dioxide, nitrogen oxides)
• Burning of fossil fuels
• Agricultural practices (ammonia)

Measures:

• Shift to cleaner energy sources
• Improve vehicle emissions standards
• Implement pollution control devices in industries
• Promote afforestation
• Reduce open burning of waste

 

Q- What are the main uses of nitrogen gas?

Main uses of nitrogen gas:

• Essential for the growth of plants and animals.
• Reacts with hydrogen to form ammonia, a key component in the production of fertilizers.
• Inert nature makes it useful for preventing oxidation in electric lamps.
• Used to create an inert atmosphere for storing certain food items, preventing spoilage.
• Liquid nitrogen is used as a cooling agent in various industrial applications, including the storage of blood and organs for transplantation.

 

Q- What is acid rain? How is it harmful for us?

Acid rain and its harmful effects:

Acid rain: It is formed when sulfur dioxide (SO2) and nitrogen oxides (NOx) from industrial emissions and vehicle exhaust react with water vapor in the atmosphere, forming acids (sulphuric acid and nitric acid).

Harmful effects:

• Damages plant leaves and causes them to fall off.
• Harms soil, water resources, and forests.
• Pollutes water sources, leading to the extinction of some fish species.
• Corrodes buildings and statues, impacting cultural heritage.
• Adversely affects human health, causing respiratory problems and skin issues.

 

Q- Air is a mixture of gases. What are they?

The main components of air are nitrogen, oxygen, argon, carbon dioxide, water vapor, and trace amounts of other gases.

 

Q- What is the ozone layer? What is its importance?

The ozone layer is a region of the Earth’s stratosphere containing a high concentration of ozone (O3) molecules. Its importance lies in absorbing the majority of the sun’s harmful ultraviolet (UV) radiation. This absorption protects life on Earth from the harmful effects of excessive UV radiation, such as skin cancer, cataracts, and damage to ecosystems.

 

Q- Which gases have the maximum percentage in the air? What are the main gases that pollute the air?

The gases with the maximum percentage in the air are nitrogen (about 78%) and oxygen (about 21%). The main gases that pollute the air include carbon monoxide, sulfur dioxide, nitrogen oxides, and particulate matter.

 

Q- Name the gases responsible for the greenhouse effect?

The gases responsible for the greenhouse effect include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and water vapor.

 

Q- Which gases are mostly present in acid rain? How do they affect our lives?

The gases mostly present in acid rain are sulfur dioxide (SO2) and nitrogen oxides (NOx). Acid rain affects our lives by causing damage to vegetation, soil, water bodies, and human-made structures. It can lead to environmental degradation, harm aquatic ecosystems, and impact human health.

 

Q- What do you understand by atmospheric pressure?

Atmospheric pressure is the pressure exerted by the air in the Earth’s atmosphere. It is the force per unit area exerted on a surface by the weight of the air above that surface in the atmosphere.

 

Q- What will happen to the human body if the air pressure of an area suddenly decreases?

If the air pressure of an area suddenly decreases, it can lead to discomfort and potential health issues for the human body. Symptoms may include ear or sinus pain, dizziness, and difficulty breathing.

 

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