Comprehensive notes, solved MCQs, and Short Questions for Class 10 Chemistry Chapter 15 Water. Covers Properties of Water, Hardness of Water (Temporary/Permanent), Water Pollution and Water Borne Diseases.
Occurrence: Ocean (97%), Glaciers/Ice caps (2.1%), Ground water (0.6%). Only 0.2% is potable.
Properties:
Soft Water: Produces good lather with soap.
Hard Water: Does not produce good lather. Causes: Dissolved Ca2+ and Mg2+ ions (Bicarbonates, Sulphates, Chlorides). Rain water dissolves Limestone (CaCO3) forming Soluble Ca(HCO3)2.
Types of Hardness:
Disadvantages: Consumes more soap, causes stomach disorders, unfit for steam engines (Boiler Scales).
Definition: Contamination of water bodies. Pollutants: Industrial effluents, Domestic sewage, Agricultural runoff.
Industrial Effluents: Heavy metals (Pb, Cd, Hg, Cr) are toxic. Cause neurological damage, kidney dysfunction, cancer.
Domestic Effluents: Detergents (Non-biodegradable) cause rapid growth of algae (Eutrophication), depleting Oxygen for aquatic life.
Agricultural Effluents: Fertilizers and Pesticides (Nitrates, Phosphates). Leaching affects ground water.
Definition: Diseases spread by drinking polluted water. Causes: Toxins, Microorganisms (Viruses, Bacteria, Protozoa, Worms), Lack of sanitation.
Diseases:
Prevention: Provision of safe water, Proper sewage disposal, Chlorination.