Ch 18 covers air and water pollution — their causes, effects, and solutions. Students learn about smog, acid rain, the greenhouse effect, ozone depletion, and how to ensure clean drinking water.
Air pollutants: carbon monoxide (vehicles), sulphur dioxide (factories), nitrogen oxides, particulates (dust, smoke). Smog = smoke + fog (reduces visibility). Acid rain: pollutant gases dissolve in rain to form acids, damaging buildings, soil, and life. Greenhouse effect: CO₂, methane trap heat → global warming. CFCs destroy the ozone layer.
Sources: untreated sewage, industrial waste, agricultural chemicals (pesticides, fertilisers). Effects: water becomes unfit for drinking, harms aquatic life, spreads diseases. Ganga Action Plan was launched to clean the Ganges. Potable water: safe for drinking. Purification: boiling, chlorination, filtration, UV treatment.
Download: https://ncert.nic.in/textbook/pdf/hesc118.pdf | Complete book: https://ncert.nic.in/textbook/pdf/hesc1ps.zip
The greenhouse effect is a natural process where certain gases (CO₂, methane) trap heat in the atmosphere, keeping Earth warm enough for life. Global warming is the enhanced greenhouse effect caused by human activities (burning fossil fuels, deforestation) that add excess greenhouse gases, raising global temperatures to dangerous levels.
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