High surface tension

Mercury is a unique liquid with a high surface tension, which is the property of a liquid that allows it to resist an external force and minimize its surface area. The spherical shape of droplets of mercury is primarily due to its high surface tension.

Surface Tension

Surface tension arises due to the cohesive forces between the molecules in a liquid. The molecules at the surface experience an unbalanced force, resulting in a net inward force that causes the liquid to behave as if it were covered by a stretched elastic skin. This phenomenon is known as surface tension.

Cohesive Forces

Cohesive forces are the intermolecular forces between the molecules of the same substance. In the case of mercury, the cohesive forces between the mercury atoms are relatively strong. These forces pull the mercury atoms closer together, giving rise to its high surface tension.

Minimization of Surface Area

The high surface tension of mercury causes it to minimize its surface area. In the absence of external forces, a droplet of mercury tends to adopt a spherical shape. This is because a sphere has the smallest surface area for a given volume, allowing the mercury to minimize its surface energy.

Balance of Forces

The spherical shape of a mercury droplet is a result of the balance between the outward force due to pressure inside the droplet and the inward force due to surface tension. The pressure inside the droplet pushes outward, while the surface tension pulls inward. The spherical shape ensures that the forces are balanced, resulting in a stable droplet.

Other Factors

While high surface tension is the primary reason for the spherical shape of mercury droplets, other factors such as adhesion and gravity also play a role. Adhesion refers to the attraction between the mercury droplet and the surface on which it rests. Gravity acts to pull the droplet downward. However, the high surface tension of mercury allows it to overcome these forces and maintain its spherical shape.

Spherical shape is basically the minimization of area and that is due to pressure difference between inside and outside. this is linked with the surface tension.

pressure difference=4*surface tension / diameter