NCERT Class-9 Science Solutions: Chapter 14-Natural Resources Part 8 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Long Answer Questions

Question 51:

How do fossil fuels cause air pollution?


The fossil fuels like coal and petroleum contain small amounts of nitrogen and Sulphur. When fossil fuels are burnt, it produces oxides of nitrogen and Sulphur. These gases cause inhalation problems and in presence of rain forms acid rain. Burning of fossil fuels also increase the amount of suspended particles in air that reduce the visibility.

Image Fossil Fuels Cause Air Pollution

Question 52:

What are the causes of water pollution? Discuss how you can contribute in reducing water pollution.


Water pollution can be caused by addition of

  1. Undesirable substances like fertilizers and pesticides or any poisonous substances.
  2. Sewage directly entering a water body.
  3. Hot water from the power plant that increases the temperature and reduces the dissolved oxygen in water thus killing the aquatic organisms.
  4. Industrial effluents or radioactive substances in water body.

We can take following measures to check water pollution

  1. The sewer lines should not be directly connected to the water body.
  2. We should not throw our garbage՚s or domestic waste in the water body.
  3. Prevent dumping of toxic compounds in the water bodies.
  4. Washing of clothes should be avoided near water bodies as it adds lot of detergents to it.
  5. Plant trees near the banks of the river to check soil erosion otherwise erosion leads to siltation of water body.
Image the Water Pollution

Question 53:

A motor car, with its glass totally closed, is parked directly under the sun. The inside temperature of the car rises very high. Explain why?


Infra-red radiations in sunlight pass through the glass and heat the interior of the car. The radiation emitted by upholstery and other inner parts of the car cannot pass out of the glass, so the heat trapped inside raises the temperature of the interior. This is because glass is transparent to infrared radiation from the sun having smaller wavelength than that emitted by the interior of the car which are of longer wavelength to which the glass is opaque.

Question 54:

Justify “Dust is a pollutant” ?


Dust remains present in air as suspended particles can cause allergy and other respiratory diseases. It also affects plant growth, by covering stomata on leaf surface. It acts as the carrier of toxic compounds like heavy metals.

Question 55:

Explain the role of the Sun in the formation of soil.


Sun helps in soil formation as Sun heats up the rocks during the day so that they expand. At night, these rocks cool down and contract. All parts of the rocks hot expand and contract at the same rate and this results in formation of cracks and finally breaking of huge rocks into smaller pieces.

Image Role of the Sun in the Formation of Soil

Question 56:

Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?


Plants require in an optimum amount for the process of photosynthesis. But, high concentration of (more than normal) is harmful and considered as a pollutant. Higher concentration of is one of the causes of greenhouse effect and global warming as it absorbs the infrared radiations thus increasing the temperature of Earth. This leads to many environmental problems.

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