When a drop of water is dropped on an oil surface, then:

Define the surface of a liquid.

The spiders and insects move and run about on the surface of water without sinking because

Explain why:
$(a)$ The angle of contact of mercury with glass is obtuse,while that of water with glass is acute.
$(b)$ Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops. (Put differently,water wets glass while mercury does not.)
$(c)$ Surface tension of a liquid is independent of the area of the surface.
$(d)$ Water with detergent dissolved in it should have small angles of contact.
$(e)$ $A$ drop of liquid under no external forces is always spherical in shape.

In a glass capillary tube,the shape of the surface of the liquid depends upon:

Force in Column-$I$ and its use in Column-$II$ are given. Match them appropriately.

Column-$I$	Column-$II$
$(a)$ Cohesive force	$(i)$ Useful for writing by chalk on blackboard.
$(b)$ Adhesive force	$(ii)$ Useful in soldering.
	$(iii)$ Useful for formation of spherical drops of liquid.