Can anyone help me with the knowledge of surface tension in liquids, thank you!

Surface tension is a manifestation of molecular force. It occurs in the boundary part when the liquid and gas come into contact. It is determined by the fact that the liquid molecules of the surface layer are in a special situation.

The molecules inside the liquid are almost next to each other, and the molecules often maintain an equilibrium distance, attracting each other if they are a little farther away, and repelling each other when they are a little closer, which determines that the liquid molecules can not diffuse infinitely like gas molecules, but can only vibrate and rotate near the equilibrium position. The molecules near the surface of the liquid are only significantly affected by the inner molecules of the liquid, and the force is uneven, so that the molecules with higher velocity can easily flush out of the liquid surface and become vapor, resulting in a sparse molecular distribution in the surface layer of the liquid (the thin layer of liquid in contact with the gas) than the internal molecular distribution. They are in a special situation relative to the distribution of molecules inside the liquid.

The repulsive force between the molecules in the surface layer decreases with the increase of their distance from each other, and the gravitational force between the molecules is dominant in this special layer. Therefore, if a dividing line MN is drawn arbitrarily on the surface of the liquid, the liquid surface is divided into two parts, A and B, as shown in the figure. f represents the attraction of molecules in the surface layer of part A to part B, and f6 represents the attraction of molecules in the surface layer of the right part to part A, and the forces of these two parts must be equal in magnitude and opposite directions.

The mutual traction of any two parts of this surface layer causes the surface layer of the liquid to shrink, and the surface of the liquid always tends to shrink as much as possible due to the surface tension, so that the small droplets in the air tend to be spherical in shape.

The magnitude of the surface tension f is proportional to the length of the dividing line Mn. It can be written as f= l or =f l.

The ratio is called the surface tension coefficient, and it is usually measured in dyn cm. Numerically, the surface tension coefficient is equal to the mutual traction force per unit length between two adjacent parts of the liquid surface.

Reference address.

1F Lao Xue Posted:2006-10-02 19:47:17

Definition 1 The concept of surface tension of liquids is described as follows: the force of mutual attraction between the surface layer on one side of any boundary line on the liquid surface and the surface layer on the other side is called surface tension; [Definition 2] The tangential component of the force that interacts between the surface layer on one side of any demarcation line on the liquid surface and the liquid on the other side (in fact, the surface double layer with a thickness of twice the thickness of the surface layer on the other side) is called the surface tension;[Definition 3] make a demarcation plane perpendicular to the liquid surface, and its intersection with the surface layer is recorded as In the force of each liquid molecule on one side on the other side of the liquid molecule, select those lines of force through , and find its resultant force t, t is the surface tension at , which is the area of the molecular stress on

It is the force between the water molecules.

Here are the surface tension values (in mn m) for some common liquids:

1. Water: 2. Ethanol:

3. Methanol: 4. N-propanol:

5. N-hexane:

6. Liquid nitrogen:

Liquids are cohesive and adsorbent, both of which are manifestations of molecular gravity. Cohesion allows the liquid to resist tensile gravitation, while adsorption allows the liquid to adhere to other objects.

At the boundary between liquid and gas, i.e. at the interface between the surface of the liquid and between two liquids that cannot be mixed, an extremely small tensile force is generated due to the attraction between the molecules. Suppose there is a thin film layer at the surface, which is subjected to the tensile force of this surface, and this tensile force of the liquid is called the surface tension.

Since surface tension exists only at the free surface of a liquid or at the interface between two liquids that cannot be mixed, the surface tension coefficient is generally used to measure its magnitude. Represents the value of the tensile force per unit length on the surface in n m. The surface tension of various liquids covers a wide range, and its value decreases slightly with increasing temperature.

In our daily life, the phenomenon of water droplets hanging on the branches but not falling after rain, and the water surface being slightly higher than the mouth of the cup without overflowing, are all the results of surface tension.

Application of surface tension

Surface tension is the result of the interaction force and attraction between the molecules of liquids, and it has an impact on many physical and chemical phenomena, so it has applications in many fields.

Here are some examples of surface tension applications:

1. Detergent: Detergent can reduce the surface tension of water, so that water can better penetrate into the fabric fiber and achieve better cleaning effect.

2. Coatings and paints: Adding some surfactants can improve the fluidity of coatings and paints, prevent them from flowing unevenly, and also improve their adhesion.

3. Underwater athletes: Underwater athletes can use the surface tension of water to reduce drag and friction to move faster.

4. Mosquito coils: Mosquito coils use the airflow formed by heat and surface tension to emit smoke and fog, thereby driving away mosquitoes.

5. Sanitary napkins: The absorbent material of sanitary napkins is usually made of fiber materials with high surface tension, which can better absorb blood.

These are just a few examples of surface tension applications, in fact, surface tension has a wide range of applications in chemistry, physics, biology and other fields.

The surface tension of a liquid refers to a mutual attraction between the molecules on the surface of the liquid, resulting in a film-like tension on the surface of the liquid. This force gives the surface of the liquid a certain elasticity and strength, which is able to resist external stretching and deformation. The surface tension arises due to the interaction forces between the molecules of the liquid, where there are mainly two forces at work.

One is the intermolecular force of attraction, also known as cohesion, which is caused by the electrostatic force between molecules, van der Waals force, or hydrogen bonding, etc. The other is the intermolecular force between the liquid and the air, known as the surface tension or liquid-gas interface tension. This force causes the molecules on the surface of the liquid to be more attractive than those inside the liquid, so the surface of the liquid appears to be less area.

Surface tension has some important properties and effects. First, the surface tension tends to shrink the surface of the liquid, making it possible to shape droplets, water droplets, etc. Second, surface tension allows some light objects (e.g. insects) to float or walk on liquid surfaces.

In addition, surface tension has an effect on the wettability of liquids and the interaction between liquids. Surface tension can be quantitatively described by measuring the deformation of the surface of a liquid, and common methods include measuring the shape of a droplet, measuring the height of a liquid rising in a pipe, and using a buoyancy balance. The unit of surface tension is usually the unit of energy divided by the unit of length, such as joule meters (j m).

In conclusion, the surface tension of liquid is a phenomenon caused by the interaction force between the molecules of liquid molding, which has an important impact on the properties and behavior of the liquid surface, and is one of the important concepts in the study of fluid mechanics.

Interaction forces between molecules.

The molecules in the surface layer are affected by the internal molecules of the liquid on the one hand, and the gas molecules on the other hand, and the molecules in the surface layer are affected by the internal molecules of the liquid on the one hand, and the gas molecules on the other hand, and the average spacing of the molecules is larger.

Therefore, the force of the liquid molecules in the surface layer is mainly manifested as gravitational force, and it is this gravitational effect between molecules that makes the surface layer have a tendency to shrink.

Among common liquids, the surface tension of water is the largest, at 20 degrees.

The surface tension of liquid metal and molten salt is greater than that of water, such as mercury at 20 degrees, iron at melting point of 1880 mn m, and sodium nitrate at 308 degrees.

Factors influencing the surface tension of liquids:

Internal factors: the surface tension of inorganic liquids is much greater than that of organic liquids;

surface tension of water;

The surface tension of organic liquids is less than that of water;

The surface tension of organic liquids containing nitrogen, oxygen and other elements is large;

The surface tension of liquids containing F and Si is the smallest;

Molecular weight, large surface tension;

Aqueous solution: if it contains inorganic salts, the surface tension is greater than that of water; Contains organic matter and has less surface tension than water.

External factors: temperature increases, surface tension decreases;

Pressure and surface tension have no relationship.

Note: The weakest liquid surface tension is alcohol.

Determination of surface tension coefficient of liquids:

The determination method of liquid surface tension is divided into static method and kinetic method. Static methods include capillary ascent method and DU

Noüy Tour Law, Wilhelmy

Disc method, rotary drop method, hanging drop method, drop volume method, maximum bubble pressure method;

Kinetic methods include ** jet method and capillary wave method. Among them, the capillary rise method and the maximum bubble pressure method cannot be used to measure liquid-

Liquid interfacial tension. wilhelmy

The disc method, the maximum bubble pressure method, the ** jet method, and the capillary wave method can be used to determine the dynamic surface tension. Due to the complexity of the kinetic method, the low accuracy of the test, and the lack of advanced data acquisition and processing methods, there are few examples of successful application of such measurement methods. Therefore, until now, the static measurement method has been mostly used in actual production.

The surface of the liquid is an attempt to reduce the surface area of the liquid.

a.That's right. b.The wrong rock has a wrong reputation.

Correct Answer: a

4 3 2 liquid tension is 2 3 sheets of liquid.

Liquid tension, the volume on both sides of the membrane changes, the pressure also changes, and the equilibrium pressure of the solution maintained by osmosis is osmotic pressure, which refers to the liquid pressure. Osmotic pressure is a property of the solution and is determined by the properties of the semi-permeable membrane. For example, the cell membrane is a semi-permeable membrane, allowing only water molecules to pass freely, and the amount of passage is controlled by the concentration of solutes on both sides of the cell membrane.

Liquid tension is commonly used to mix liquids

1 solution: It is a mixed solution of 1 part of 5% glucose solution and 1 part of sodium chloride, and its osmolality pressure is about half of that of plasma, that is, 1 2 sheets, which is suitable for liquid replacement for simple vomiting and continued fluid loss.

The simple preparation method of preparing the ant liquid can be 500ml of 5% glucose and 20ml of 10% sodium chloride solution.

2:1 solution: a mixture of 3 parts of 10% glucose solution, 2 parts of sodium chloride solution and 1 part of sodium lactate (or sodium bicarbonate) solution. The simple preparation method is: 500ml of 5% glucose solution is added to 15ml of 10% sodium chloride solution and 15ml of sodium lactate solution (24m of 5% sodium bicarbonate solution), and the tension of fibrillation is 1 2 sheets.

: 4:2 liquid (Some units change the order of the mixture to 4:.)

3:2 solution): It is a mixed solution of 3 parts of 10% glucose solution, 4 parts of sodium chloride solution and 2 parts of gram molecule) sodium lactate solution (or sodium bicarbonate solution), the total number of parts is 9, of which electrolyte (with osmolality) accounts for 6 parts, so it is 6 9 sheets, simplified to 2 3 sheets (about equivalent to 2 3 of plasma osmolality, that is, 2 3 sheets).

It is mainly used to replace the amount of fluid that has been lost (i.e., the amount of accumulated loss).

Sheet. Sheet.

Sheet. Zhang quietly.

e.Wait for a sheet. The correct answer to the case: Que Xun D