- No.6. Differentiate between soft and hard water
Answer. Soft water is that which produced good lather with soap. While hard water is that which does not produce lather with soap?
Hard water consists of salts of divalent cations like Mg2+, Ca2+, and anions like Cl-, SO42- ,HCO3– and CO32- for example, gypsum (CaSO4.2H2O) and limestone (CaCO3) in water while soft water contains these salts.
- No.7. What are the causes of hardness in water?
Answer. Causes of hardness in water are presence of salts of divalent cations like Mg2+, Ca2+, and anions like Cl, SO42-, HCO3– and CO32– for example, gypsum (CaSO4.2H2O) and limestone (CaCO3) in water.
- No.8. What are the effects of temporary hardness in water?
Answer. Temporary hardness is because of presence of bicarbonate s of calcium and magnesium.
Effects of hard water
(i) Hard water consumes large amount of soap in washing purposes.
(ii) Drinking hard water causes stomach disorders.
(iii) Hard water is unfit for use in steam engines, boilers and turbines because insoluble calcium and magnesium salts are deposited inside. Which is called scale? They are bad conductors of heat and hence more fuel is used. Insoluble calcium and magnesium sulphates not only reduce the efficiency of the engine but also cause the boiler to burst.
- No.9. Mention the disadvantages of detergents.
Answer. The detergent remains in the water for a long time and makes the water unfit for aquatic life. The phosphate salts present in detergents causes’ rapid growth of algae in water bodies, which floats over the surface of water. These plants ultimately die and decay. Decaying plants being bio-degradable consume O2 present in water. Thus, depletion of O2 results in death of aquatic life.
- No.10. What is difference between biodegradable and non-biodegradable substances?
Answer. The substances which can be decomposed by micro-organism like bacteria are called biodegradable substances. While, some of the detergents cannot be decomposed by micro-organisms like bacteria; they are called non-biodegradable substances.