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Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged.
This assumption is approximately fulfilled for most known liquids. When plotting the surface tension versus the temperature a fairly straight line can be seen which has a surface tension of zero at the critical temperature. The Eötvös rule also gives a relation of the surface tension behaviour of different liquids in respect to each other: 2.
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).
Liquids 1 and 2 fully wet the surface as shown by their low contact angles, so they should be neglected when first drawing the line of best fit to find the critical liquid surface tension needed to effectively wet the PC surface, γ C, which is simply the x-intercept of the best fit line for the Zisman Plot.
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
Three examples of droplet detachment for different fluids: (left) water, (center) glycerol, (right) a solution of PEG in water. In fluid dynamics, the Plateau–Rayleigh instability, often just called the Rayleigh instability, explains why and how a falling stream of fluid breaks up into smaller packets with the same total volume but less surface area per droplet.
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.
In the equation, m 1 and σ 1 represent the mass and surface tension of the reference fluid and m 2 and σ 2 the mass and surface tension of the fluid of interest. If we take water as a reference fluid, = If the surface tension of water is known which is 72 dyne/cm, we can calculate the surface tension of the specific fluid from the equation.