van der waals

Surface Tension and Contact Angle
Knowledge of surface tension and contact angle has a very large role of particles in life. For example, the liquid will spread on the surface or it will be small droplets depends on the properties of the material or fluid.
Surface tension is the force caused by an object acting on the surface of the liquid along the surface that touches it. If F = force (newtons) and L = length (m), the voltage-surface, S can be written as S = F / L. The surface tension caused by the interaction of liquid molecules on the surface of the liquid. In the fluid inside a molecule surrounded by other molecules around it, but there is no liquid on the surface of another molecule at the top of the liquid molecules. This led to the emergence of molecular restoring force is attractive when it is lifted away from the surface of the molecule, the molecule that is in the bottom surface of the liquid. Conversely, if the molecules on the surface of the liquid is pressed
Capillarity is caused by the interaction of the molecules in the liquid. In the liquid molecules can be subjected to adhesion and cohesion. Style of cohesion is the attraction between molecules in a liquid while the adhesion force is the attraction between molecules with other molecules that are not similar, ie materials in which the liquid container is located. If the adhesion is greater than the cohesion as in water with a glass surface, the water will interact strongly with the surface of the glass so the water over the glass and the liquid surface will be curved (concave). This situation can cause the liquid to rise to the top of the surface tension limit of him up until the upward force to balance gravity fluid is reached. So the water can rise up in a small tube called a capillary tube. This is what happens when the water rises from the ground up through the wall.