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## Difference Between Surface Tension and Surface Energy

Surface Tension vs Surface Energy

Surface tension and surface energy are two very important concepts discussed in physics. The concepts of surface tension and surface energy are widely used in fields such as fluid mechanics, fluid dynamics, aerodynamics and various other fields. Surface tension is the net intermolecular force on the surface molecules of a liquid. Surface energy is the relevant energy of these bonds. In this article, we are going to discuss what surface tension and surface energy are, their applications, the definitions of surface tension and surface energy, their similarities, and finally the difference between surface tension and surface energy.

Surface Tension

Consider a homogeneous liquid. Every molecule in the central parts of the liquid has exactly same amount of force pulling it to every side. The surrounding molecules are pulling the central molecule uniformly on every direction. Now consider a surface molecule. It has only forces acting upon it toward the liquid. The air – liquid adhesive forces are not even nearly as strong as the liquid – liquid cohesive forces. So, the surface molecules get attracted towards the center of the liquid, creating a packed layer of molecules. This surface layer of molecules acts as a thin film on the liquid.

If we take a real life example of a water strider, it uses this thin film to place itself on the surface of the water. It slides on this surface layer. If it isn’t for this surface layer, it would have drowned immediately.

Surface tension is defined as the force parallel to the surface perpendicular to a unit length line drawn on the surface. The units of surface tension are Nm-1. Surface tension is also defined as energy per unit area. This also gives surface tension new units Jm-2.  Surface tension that occurs between two immiscible fluids is known as the interfacial tension.

Surface Energy

Surface energy and surface tension are two interconnected concepts. The molecules on the surface of a liquid are packed due to unbalanced intermolecular forces than the molecules at the center. This means there is a high energy density at the surface of a liquid.

Surface energy can be defined as the energy difference between the bulk of the material and the surface of the material. Surface energy is defined as the surface energy per unit surface area. The surface energy per unit area is identical to the surface tension measured. The units of surface energy are Jm-2. When the surface energy is provided by an external source, the liquid is said to be bubbling.

Surface Tension vs Surface Energy

• Surface tension has the units of Nm-1 and Jm-2 whereas surface energy has the unit Jm-2.
• Surface tension is measured along a line whereas surface energy is measured along an area.

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