Class 7 Chemistry – CHAPTER 4 : ACIDS,BASES AND SALTS

Acids, Bases and Salts Chemicals can be broadly classified into three categories, acids, bases and salts. Acids Examples: Hydrochloric acid and sulphuric acid are corrosive acids. Carbonic acid is a non-corrosive acid. Organic acids: Naturally occurring acids obtained from plants and animals. Mineral acids: They are obtained from minerals present in the Earth’s crust. Bases […]

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Class 7 Biology – CHAPTER 13 : WASTEWATER STORY

Wastewater Story Water – Our Lifeline Sewage Types of Impurities Examples Organic impurities Human faeces, animal wastes, oil, urea, pesticides,herbicides, fruit and vegetable wastes Inorganic impurities Nitrates, phosphates, metals Nutrients Phosphorus and nitrogen Bacteria Those which cause diseases such as cholera, dysentery andtyphoid Sources of wastewater: Treatment of sewage in cities and towns: If sewage

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