用拉脱法测液体表面张力系数（The surface tension coefficient of the liquid is measured by the pull - off method）.doc

用拉脱法测液体表面张力系数（The surface tension coefficient of the liquid is measured by the pull - off method） The surface tension coefficient of the liquid is measured by the pull - off method Liquid has the tendency to minimize its surface, as if the liquid surface is a strained rubber film. The force along the surface of the contraction surface is called the surface tension. The presence of surface tension can indicate many phenomena peculiar to the liquid state, such as the formation of foam, wetting and capillary phenomena, etc. In industrial technologies, such as mineral flotation techniques and liquid transport techniques, surface tension is studied. There are many methods to determine the surface tension of liquid, such as drawing, capillary, and maximum bubble pressure. In this experiment, a direct method is used to determine the method. [experimental purpose] 1, study the principle and method of measuring the small force of a coking scale. Understand the properties of liquid surface and measure the surface tension factor of the liquid. [experimental principle] The liquid surface layer (whose thickness is equal to the radius of the molecule) is different from the molecules inside the liquid. Inside the liquid, each molecule is surrounded by other molecules of the same kind, and the force of the forces surrounding it is zero. By the gas phase on the top of the liquid layer very few number of molecules, each a molecule inside the surface layer of the gravity of the smaller than downward gravitational pull up, resultant force is not zero, the resultant force is perpendicular to the surface and point to the liquid inside, as shown in figure 4.15 1, so molecules tend to from inside the liquid level in liquid, and liquid surface natural contraction, until in dynamic equilibrium, namely, at the same time from the liquid surface into the liquid inside the number of molecules and equals the number of molecules to the liquid surface due to thermal motion. FIG. 4.15-1 liquid surfa