液体表面张力的测定（Determination of liquid surface tension）Experiment five
有一个地方Experiment five, experiment five
装表接电Experiment five
Determination of liquid surface tension
Determination of surface tension of liquids - Determination of surface tension of liquids
Determination of liquid surface tension
Two billion eight million two hundred and one thousand two hundred and five
2008201205 2008201205
2008201205 Liu nior advir
Liu Zizheng Liu Zizheng
Liuzizheng
1 objective (1) to measure the surface tension of different concentrations of ethanol aqueous solution, and calculate the surface adsorption amount and the transver of ethanol molecule
Sectional area.
(2) understand the nature of surface tension and the relationship between surface tension and adsorption capacity.
(3) grasp the principle of maximum bubble pressure method to determine the surface tension and surface adsorption capacity of solution. 2 the principle of experiment is that in a liquid, the attraction of any molecule is balanced. But on the surface of the liquid
Molecules are not the same. Becau the molecules on the surface layer are attracted by the inner layer molecules on the one hand, and on the other hand, the molecules are expod to the surface layer
The attraction of the gas molecules outside the liquid is greater than that of the latter. Therefore, on the surface layer of liquid surface
In this ca, each molecule is subjected to an unbalanced force that is perpendicular to and pointing
to the interior of the fluid. This attraction makes the surface visible
The molecules push inward to produce the smallest area of the liquid. In order to increa the surface area of liquid, it is necessary to resist molecules
Increa the potential energy of a molecule by working inward. So the molecules in the surface layer are larger than in the liquid称谓礼仪
Potential energy, which is the surface free energy, usually increas A of the maximum work required to increa the surface of a square meter
G change of surface free energy by a square meters, known as the surface unit surface energy, and its unit is J - m-1;
The force acting on the surface of the liquid and the unit length of the unit that is trying to shrink it is called surface tension
The unit of force is N. M-1. The surface energy of a liquid unit surface is equal to its surface tension in numerical terms.
If the surface area of liquid is incread by S, the reversible work A should be ud:
wps云空间
-A = G = gamma S (1)
The surface tension of liquid is related to temperature. The higher the temperature is, the smaller the surface tension is. When the critical temperature is reached,
The surface tension tends to zero when the liquid and gas are parated. The surface tension of the liquid is also related to the purity of the liquid
In pure liquid (solvent), if the impurity (solute) is added, the surface tension will change, and the change will be great项脊轩志
Small, depends on the nature of the solute and the amount of added.
For pure solvents, the surface layer and the internal composition are the same, but not for the solution. When
When the solute is added, the surface tension of the solvent changes. According to the principle of minimum energy, if solute can reduce dissolution
The solute concentration in the surface layer should be larger than that in the solution, if the solute energy is added
If the surface tension of the solvent is raid, then the solute concentration in the surface layer should be lower than that in the solution. this
The phenomenon that the surface concentration is different from the solution concentration is called surface adsorption of solution. At a certain temperature and pressure
The amount of solute adsorbed on the solution surface and the surface tension of the solution and the added mass (i.e., the concentration of the solution)
The relation between them can be expresd by Gibbs (Gibbs) formula:
Type: for the adsorption of mol.m (gamma
桃的营养价值Solution concentration (mol.L-1); R
Gas constant
The change rate of surface tension with the concentration of solution at temperature
背叛的眼泪Gamma? /? C) T <0, >0, gamma surface layer, the concentration is greater than the concentration of the internal solution棕熊图片
Effect。 If the gamma increas with the increa of concentration, i. e.
The concentration is less than the concentration of the solution itlf,
The adsorption of solutes and concentration of C
C/ gamma map, a straight line,
If N reprents the number of solutes on the surface of 1m2
The L is Avogadro constant in the formula
It can be en from the formula (2) that only the concentration and surface tension of the solution can be determined
The adsorption amount of gamma solution.
In this experiment,
The determination of solution concentration is the corresponding relationship between applied concentration and refractive index
