GENERAL KNOWLEDGE

Detailed explanation-1: -Mercury has force of adhesion less than the force of cohesion and hence prefers to stick to itself rather than the glass surface. To achieve this, mercury takes the spherical shape to minimize its contact with the glass surface.

Detailed explanation-2: -Answer: Option C Solution: On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because cohesion of mercury is greater than its adhesion with glass.

Detailed explanation-3: -Why does mercury collect itself into drops when placed on a clean glass plate? Answer: The adhesive force between mercury and glass molecules is less than the cohesive force between mercury molecules. So instead of sticking to glass, mercury collects itself into drops.

Detailed explanation-4: -In the case of mercury the mercury glass, angle of contact is obtuse. To obtain this obtuse value of angle of contact, mercury tends to form a drop. But in the case of water, the water-glass angle of contact is acute. Thus the water tends to spread out to achieve this acute angle of contact.