Definitions [10]
The envelope of air around the Earth is called the atmosphere. It is composed of nitrogen, oxygen, water vapour, and carbon dioxide, with other gases present in small quantities. The atmosphere is like a protective blanket that keeps our planet safe and helps support life.
Define the following:
Respiration
Respiration: Respiration is a chemical process that takes place in all living beings (slow in plants). In this process, oxygen present in inhaled air reacts with the digested food material in the body. This results in the release of energy, carbon dioxide, and water.
Sugar + Oxygen → CO2 + Water + Energy.
Define rusting?
Rusting: Slow conversion of iron into its hydrated oxide in the presence of moisture and air is called rusting.
Define the term Global warming.
Global warming : An increase in the percentage of carbon dioxide, methane, nitrous oxide and chlorofluorocarbon traps the heat causing the temperature of the earth and its surroundings to rise. This is known as global warming.
Define the following:
Combustion.
Combustion: Combustion also called burning “is burning of substance in the oxygen of air completely producing heat and light is called combustion.”
Define the term smog.
Smog : Oxides of nitrogen form a mixture of smoke and fog known as smog which affects our eyes too.
Air pollution means degradation of the air quality which harmfully affects the living organisms as well as certain objects.
or
Contamination of air by harmful substances like poisonous gases, smoke, particulate matter, microbes, etc., is called air pollution.
Define ‘eutrophication’.
Eutrophication: “Organic matter in sewage poured into water bodies generally results in excessive growth of algae – which deoxygenates water and produces deadening atmosphere there.”
Define – Saline water.
Water with a large amount of dissolved solids is not potable or suitable for drinking. Such water is called saline water.
Define – Scarcity of water.
There is no change in the total quantity of water available on the earth. It remains the same. But the water useful for plants, animals, and man is decreasing day by day. It is called the Scarcity of water.
Key Points
- Air pollutants are of two types - particulate (smoke, smog, dust, heavy metals) and gaseous (CO₂, CO, SO₂, NO, NO₂). PM2.5 particles cause the greatest harm, penetrating deep into the lungs, causing irritation and breathing disorders.
- NO₂ + water vapour = nitric acid, causing irritation to eyes, lungs, liver and kidneys. CO is a poisonous gas produced by the incomplete combustion of fuel.
- Three control mechanisms - Electrostatic Precipitator (removes 99% soot/dust from industrial exhaust), Exhaust Gas Scrubber (removes SO₂ using lime/water spray), Catalytic Converter (removes poisonous gases from automobile exhaust; requires unleaded petrol).
- Delhi was 4th most polluted city in 1990. Following Supreme Court orders, all city buses were converted to CNG by 2002 — economic, efficient and adulteration-proof.
- India adopted BS-VI emission standards in 2018, skipping BS-V, reducing CO₂ and SO₂ levels in Delhi.
