Chapter- 18 Pollution of Air and Water Class 8 Notes

Pollution of Air and Water Class 8 Notes

Air Pollution

Question: What is Pollution?

  • Pollution word comes from the latin word ‘Polutus’ meaning to make dirty or it simply means contamination.
  • Pollute means to make something unclean, impure, and unhealthy.
  • So, we can define Pollution as “the addition of harmful substances or contamination of the environment that has harmful effects on plants, animals, and human beings”.
  • Pollution can be also defined as the action or process that makes the land, water, air etc. not suitable or safe to use.


Question: What are Pollutants?

  • A pollutant is defined as any solid, liquid, gaseous substance present in such concentration as may be or temd to be injurious to the environment. (The Indian Environment (Protection) Act, 1986.
  • The agents that causes pollution are called pollutants.
  • Pollutants can be natural (volcanic ash, forest fire etc.) or man-made (industrial wastes etc.).

Types of Pollution

There are mainly types of Pollution.

  1. Air Pollution
  2. Water Pollution
  3. Soil Pollution
  4. Noise Pollution
  5. Radioactive Pollution
  6. Thermal Pollution

Air Pollution

Question: What is Air Pollution?

According to the WHO, air pollution is defined as the presence of different substances in a certain concentration in the air that causes harm to human beings and the environment.

The contamination of air due to harmful and undesirable (quantity and quality) substances affecting the living and non-living things on the earth.


  • SPM stands for Suspended Particulate Matter.
  • SPM are microscopic particles of solid or liquid matter suspended in the air.
  • Pollutants that do not dissolve or mix in water due its larger size molecule.
  • These are called particulate matter.
Power Plants, Domestic Burning, Construction Work, etc.Air Pollution, Acid Rain

Acid Rain

Oxides of Sulphur and Nitrogen, presnt in the air as pollutants react with water to form Sulphuric Acid and Nitric Acid.

These acids makes the rainwater significantly acidic, and such rain is called Acidic Rain.

pH of Acid rain is less than 5.6, and has adverse effects on the animal skin, marbles and agriculture etc.

In some industrial areas hcl gas is present in the atmosphere, and it dissolves with water to form Hydrochloric acid, making it more acidic.

Effects of Acid Rain

  • make water unsuitable for aquatic plants and animals.
  • Soil becomes acidic and thus unsuitable for cultivation.
  • Sculptures, monuments, and buildings are damaged or eroded. Ex: Taj Mahal

Case Study: Taj Mahal

  • Marble is composed of carbonate minerals, normally calcite (CaCO3) and dolomite (MgCO3. CaCO3).
  • Acid rain reacts with the Calcium carbonate present in white marble of Taj Mahal.
  • As a result of chemical reaction, nitrates and sulphates of calcium are formed which turns the white marble into yellow.
  • Along with carbon dioxide and water.

CaCO3 + H2SO4 → CaSO4 + H2O + CO2

CaCO3 + HNO3 → Ca(NO3)2 + H2O + CO2

Marble Cancer

Question: What do you understand by Marble Cancer?

Answer: Acid present in the Acid rain reacts with Marble and corrode it slowly or eat up the marble of the Taj Mahal. This phenomenon is called Marble Cancer.

Chapter 17: Stars and the Solar System Class 8 Notes


  • It is an enclosure of glass to protect the plants from cold air. This glass traps the heat of the sun and make the air inside warmer.
  • The greenhouse effect is a process that occurs when gases in Earth’s atmosphere trap the Sun’s heat.
  • This process makes Earth much warmer than it would be without an atmosphere.
  • Without greenhouse gases, the average temperature of Earth’s surface would be about -18 °C (0 °F), rather than the present average of 15 °C (59 °F).
  • The greenhouse effect is one of the things that makes Earth, a comfortable place to live.

Greenhouse Gases

  • Any gas that has the property of absorbing infrared radiation (net heat energy) emitted from Earth’s surface and reradiating it back to Earth’s surface, thus contributing to the greenhouse effect.
  • Primary greenhouse gases are- Water Vapor, Carbon di oxide (CO2), Nitrous Oxide (N2O), Methane (CH4), Ozone (O3).

Global Warming

Global warming is the long-term heating of Earth’s climate system observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth’s atmosphere.

Methods of Reducing Air Pollution

  • Afforestation
  • Modyfying Automobile Engines
  • Use of CNGs
  • Use of Unleaded Petrol: lead was added with petrol run automobiles smoothly
  • Using cleaner sources of energy
  • Removing pollutants from industrial waste
  • Social Campaign to create awareness among people

Water Pollution

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