Surface Tension 101
Surface tension is a property of the surface of a liquid that causes it to behave as an elastic sheet. It allows insects, such as the water strider to walk on water. It allows small objects, even metal ones such as needles, razor blades, or foil fragments, to float on the surface of water, and it is the cause of capillary action. An everyday observation of surface tension is the formation of water droplets on various surfaces or raindrops.
The physical and chemical behavior of liquids cannot be understood without taking surface tension into account. It governs the shape that small masses of liquid can assume and the degree of contact a liquid can make with another substance.
Applying Newtonian physics to the forces that arise due to surface tension accurately predicts many liquid behaviors that are so commonplace that most people take them for granted. Applying thermodynamics to those same forces further predicts other more subtle liquid behaviors.
Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent — but when referring to energy per unit of area people use the term surface energy — which is a more general term in the sense that it applies also to solids and not just liquids.
Surface Tension 101 should include one of the most basic liquids…. Water… It gives a good point of reference that people can identify with.
The surface tension of water is 72 dynes/cm at 25°C . It would take a force of 72 dynes to break a surface film of water 1 cm long. The surface tension of water decreases significantly with temperature. The surface tension arises from the polar nature of the water molecule.
Hot water is a better cleaning agent because the lower surface tension makes it a better “wetting agent” to get into pores and fissures rather than bridging them with surface tension. Soaps and detergents further lower the surface tension.
Like the new blog and its layout, thanks
Gus