Wicking Properties - Surface Energy Cohesive Forces

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Surface Energy Cohesive Forces

Have you ever wondered why raindrops are spherically shaped? It’s because of surface tension – or surface energy. Surface energy is a characteristic property of a liquid. The amount of surface energy in a liquid is directly related to the liquid’s surface area. High surface area geometries contain high surface energy levels. Low surface area geometries contain low surface energy levels.

A liquid - like matter of all forms - is constantly in search of low energy states or geometries. Because the sphere has the smallest surface area for any geometric volume it also has the lowest energy state. Therefore, liquids attempt to form themselves into spherical shapes in an effort to lower their overall energy state. Another way of looking at the driving force behind spherically shaped liquids involves the cohesive forces of the molecules in the liquid. Cohesive forces are the attractive forces that a liquid’s molecules have to one another.

Click here to view the Surface Energy Cohesive Forces animation.

Molecules positioned at the surface of a liquid do not have cohesive molecular neighbors on all of their sides – only on their interior sides. Therefore, they are only attracted toward the interior region of the liquid. When all of the molecules located on the liquid’s exterior surface get simultaneously attracted or pulled toward the interior region of the liquid, a sphere forms in an effort to balance the internal and external forces acting on the droplet’s surface. Hence, the sphere represents the most geometrically favorable energy shape. It is for this reason that liquids take on the shape of a droplet or sphere ... and it is for this reason that raindrops do as well.

Wicking Properties

Pore Size Distribution - Capillary Flow
Water Flow vs Differential Pressure
Capillary Theory
Interfacial Surface Energy and Contact Angle
Capillary Force, Capillary Pressure & Capillary Head

Pore Size Distribution - Mercury Intrusion
Water Intrusion Pressure
Surface Energy Cohesive Forces
Contact Angle in a Capillary
Capillary Theory Conclusion

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