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Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. [4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to ...
'drop') is one of the most common methods for measuring surface tension. The principle is to measure the weight of drops of a fluid of interest falling from a capillary glass tube, and thereby calculate the surface tension of the fluid. We can determine the weight of the falling drops by counting them. From it we can determine the surface tension.
Drop of water bouncing on a water surface subject to vibrations Surface tension prevents water droplet from being cut by a hydrophobic knife. Liquid forms drops because it exhibits surface tension. [1] A simple way to form a drop is to allow liquid to flow slowly from the lower end of a vertical tube of small diameter.
(σ: surface tension, ΔP max: maximum pressure drop, R cap: radius of capillary) Later, after the maximum pressure, the pressure of the bubble decreases and the radius of the bubble increases until the bubble is detached from the end of a capillary and a new cycle begins. This is not relevant to determine the surface tension. [3]
The spinning drop method is convenient compared to other widely used methods for obtaining interfacial tension, because contact angle measurement is not required. Another advantage of the spinning drop method is that it is not necessary to estimate the curvature at the interface, which entails complexities associated with shape of the fluid drop.
A classical torsion wire-based du Noüy ring tensiometer. The arrow on the left points to the ring itself. The most common correction factors include Zuidema–Waters correction factors (for liquids with low interfacial tension), Huh–Mason correction factors (which cover a wider range than Zuidema–Waters), and Harkins–Jordan correction factors (more precise than Huh–Mason, while still ...
This may be written in the following form, known as the Ostwald–Freundlich equation: =, where is the actual vapour pressure, is the saturated vapour pressure when the surface is flat, is the liquid/vapor surface tension, is the molar volume of the liquid, is the universal gas constant, is the radius of the droplet, and is temperature.
For example, a drop of liquid will adopt a given contact angle when static, but when the surface is tilted the drop will initially deform so that the contact area between the drop and surface remains constant. The "downhill" side of the drop will adopt a higher contact angle while the "uphill" side of the drop will adopt a lower contact angle.