Surface Tension and Surface Energy

All matter is composed of molecules, and each molecule has variable degrees of attraction to the molecules around it. Because of this intermolecular attraction, the molecules in your drink, or even the ice in your drink, stay together in a glass or as a puddle on the table top rather than drifting away into the air. The surface tension of a liquid is the attraction force of the molecules present at its surface towards one another. Surface energy is the analogous attractive force that exists between molecules at a solid substance’s surface. This attracting force is responsible for holding a material together in a coherent form.

Surface Tension

Surface tension is the feature of any liquid surface that exposes itself as if it were a stretched elastic membrane. This effect may be seen in the roughly spherical form of tiny liquid droplets and soap bubbles. Certain insects may float on the surface of water due to this feature. Surface tension forces are not the same as gravitational forces. The important distinction is that gravitational forces scale with mass, hence the gravitational force between two molecules is small to zero. We all cling to the Earth so tightly because the globe has such a large mass that it exerts a powerful gravitational attraction on us. On the other hand, it is caused by the attraction of opposite electrical charges caused by electron dispersion around molecules. Surface tension is the force necessary to overcome these attractions and separate molecules on the surface of a liquid. However, if you draw an imaginary line on the surface of a liquid film or bubble and then try to pull it apart, the force necessary to pull and split the liquid at that line, divided by the length of the line, is the liquid’s surface tension.

Formula

Surface tension is described mathematically as the force (F) acting on the surface and the length (l) of the surface, hence it is given as:
T = F / l.
The surface tension is sometimes defined as the ratio of work done (W) to change in surface area (A).
T = W / A.
It has the SI unit of N/m or J/m and the dimensional formula [M L⁰ T-²].

Surface Energy

Surface energy quantifies the breaking of intermolecular connections produced by surface development. It is also known as surface free energy and interfacial free energy. The work done per unit area by the force that generates the new surface is known as surface energy. When a liquid’s free surface area is raised, an effort must be made to overcome the force of surface tension. On the liquid surface, this work is stored as potential energy. Surface energy is the increased potential energy per unit area of a free liquid surface.

Formula

Surface Energy = Energy/Area
Surface Energy (E) = S x ΔA,
Where S is surface tension and ΔA is surface area increased.

Difference between Surface Tension and Surface Energy

S.NO	Surface Tension	Surface Energy
1	The force parallel to the surface perpendicular to a unit length line drawn on the surface is defined as surface tension.	Surface energy is defined as the energy differential between the bulk of a substance and its surface.
2	Surface tension is measured in Nm-1 and Jm-2 units.	Surface energy is measured in Jm-2 units
3	Surface tension is measured in a straight line	Surface energy is measured in an area
4	Surface tension refers to the attractive attractions of liquid molecules	surface energy refers to the same interactions between molecules of a solid material

What is Capillary?

When a thin tube is immersed in water, the water rises to a specific level inside the tube. This sort of tube is known as a capillary tube, and the phenomena it describes is known as the capillary effect. The meniscus effect is another term for the capillary effect. The surface tension force causes the capillary effect. The capillary rise and depression occur as a result of intermolecular cohesion and adhesion. The force of adhesion between the tube surface and a water molecule is greater than the force of cohesion between water molecules. As a result, the water molecules on the tube surface have a concave form.
In a tiny diameter tube, the weight of the liquid might rise or fall
= area of tube ×rise or fall ×specific weight
= (π/4 ×d²×h) w

Conclusion

The surface tension of a liquid is the attraction force of the molecules present at its surface towards one another. Surface tension is the force necessary to overcome these attractions and separate molecules on the surface of a liquid. Surface energy is defined as the energy differential between the bulk of a substance and its surface. When a liquid’s free surface area is raised, an effort must be made to overcome the force of surface tension. Moreover in this article the capillary tube is also described so that the concept related to surface tension and surface energy will get cleared. Hope this article is useful for your academics.