Clear, transparent water is always fit for drinking.' Comment.

How can water be made safe for drinking?

Stability of a crystal is reflected in the magnitude of its melting point'. Comment. Collect melting points of solid water, ethyl alochol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?

Science, like any knowledge, can put to good or bad use, depending on the user. Given below are some of the applications of science. Formulate your views on whether the particular applicatioa is good, bad -orsomething that cannot be so clearly, categorized : (a) Mass vaccination against small pox to curb and finally eradicate this disease from the population. (This has already been successfully done in India). Television for eradiction of illeteracy and for mass communication of news and ideas. Prenatal sex determination Computers for increase in work efficiency.. . Puttiing artificial satellites into orbits around the Earth. Development of nuclear weapons. Development of new and powerful technique of chemical and biologicaal warfaree. Purificaitoin of water for drinking. plastiic Surgery and cloning.

Explain the following observations: Alum is added to purity drinking water.

Half of a herd of deer are grazing in the field and three fourths of the remaining are playing nearby. The rest 9 are drinking water from the pond. Find the number of deer in the herd.

Write two application of colloid in the purification of drinking water and in photographic plates & film.

Why does a needle float on clear water, but sinks when some detergent is added to water?

A sample of drinking water was found to be severely contaminated with chloroform (CHCl_3) supposed to be a carcinogen. The leve of contamination was 15 ppm (by mass): express this in percent by mass.

Sample of drinking water was found to be severely contaminated with chloroform. CHCl_3 . Supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass). Express this in percent by mass.