Question

The spherical shape of the rain-drop is due to Surface tension.Explain

Answer 1

Hint: Sphere has the least surface area for a given volume.Shape of the liquid contained things is determined by the various factors.

Complete answer:
When the surface area of the liquid is increased, molecules from the interior rise to the surface. In this process, work is done by the molecules against the intermolecular forces and the energy is stored as potential energy. In a stable equilibrium the system tries to minimize this potential energy and hence tries to minimize the surface area. This property is exhibited as surface tension. The surface tension of a liquid is defined as the force per unit length in the plane of the liquid, acting at right angles on either side of an imaginary line drawn in that surface. It has an S.I. unit if N/m.
As a result of it, a raindrop in absence of any external force tries to minimize its surface area. For a given volume of liquid, the sphere has the minimum surface area. Thus, a rain-drop is spherical in shape.

Note:
As mentioned in the absence of any external force, the rain drop is spherical. However, while falling on earth, it is also acted upon by gravity. Gravity distorts the shape, and stretches the sphere to a droplet shape. Density of the liquid has nothing to do with the shape of it. Also considering the droplet to be small, the atmospheric pressure acts equally on all sides, thus preserving the spherical shape.