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γ is the surface tension of the liquid in dynes per centimeter or newtons per meter. g is the acceleration due to gravity and is equal to 980 cm/s 2 or 9.8 m/s 2; ρ is the density of the liquid in grams per cubic centimeter or kilograms per cubic meter; Illustration of how lower contact angle leads to reduction of puddle depth
In the derivation of Washburn's equation, the inertia of the liquid is ignored as negligible. This is apparent in the dependence of length L {\displaystyle L} to the square root of time, L ∝ t {\displaystyle L\propto {\sqrt {t}}} , which gives an arbitrarily large velocity dL/dt for small values of t .
The contact angle (symbol θ C) is the angle between a liquid surface and a solid surface where they meet. More specifically, it is the angle between the surface tangent on the liquid–vapor interface and the tangent on the solid–liquid interface at their intersection. It quantifies the wettability of a solid surface by a liquid via the ...
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface. Right: The reduction in flux passing through a surface can be visualized by reduction in F or dS equivalently (resolved into components, θ is angle to ...
Meniscus formation is dependent on the surface tension of the liquid and the shape of the capillary, as shown by the Young-Laplace equation. As with any liquid-vapor interface involving a meniscus, the Kelvin equation provides a relation for the difference between the equilibrium vapor pressure and the saturation vapor pressure.
During this process, surface tension decrease as function of time and finally approach the equilibrium surface tension (σ equilibrium). [3] Such a process is illustrated in figure 1. (Image was reproduced from reference) [2] Figure 1: Migration of surfactant molecules and change of surface tension (σ t1 > σ t2 > σ equilibrium).
The density, molar mass and the critical temperature of the liquid have to be known. At the critical point the surface tension is zero. The first assumption of the Eötvös rule is: 1. The surface tension is a linear function of the temperature. This assumption is approximately fulfilled for most known liquids.
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.