What is the height of the water film in the measurement of the surface tension coefficient of liquid

The thickness can be changed by air pressure, and there is no exact value.

Procedure. 1.Install and debug the instrument. Install the bracket, install and hang the spring mirror, weight disc and wire frame, etc., adjust the screws of the bracket base to make the metal rod straight, so that the small mirror is suspended in the glass tube.

2.Determination of the stubbornness coefficient k of the Jorchy scale. First of all, adjust the bracket lifting knob so that the horizontal line C on the small mirror, the horizontal line D on the glass tube and the image D D in the small mirror "three lines coincide", and the ruler reading X0 is noted; Secondly, the same amount of small weights (one by one into the weight disc, each weight added, should re-adjust the lifting knob to make the "three lines coincide", and then read out the vernier position xi (generally take i 9); Finally, reduce the weight one by one, each subtract one, still need to adjust the lifting knob to make the "three lines coincide", and then read out the position of the cursor, and the position of the vernier corresponding to xi is recorded as.

The data are processed by the difference-by-difference method to find the stubbornness coefficient k and the uncertainty.

3.Determination of the surface tension coefficient of water.

The width l of the wire frame was measured with vernier calipers, and the average was averaged by repeated measurements 5 times.

Place a glass beaker with an appropriate amount of water on the loading platform of the stand, wash the wire frame with alcohol and hang it on a small hook under the weight tray.

Adjust the height of the stage and the lift knob so that the filament is completely immersed in water.

Under the condition of ensuring the "three-line coincidence", adjust the lifting knob with one hand and the height of the stage with the other hand to When the upper edge of the wire frame is just level with the water surface, note the position of the upstream mark x0 of the bracket.

Under the condition of ensuring the "three-line coincidence", continue to slowly adjust the lifting knob and the stage until the wire frame is just out of the liquid surface, and note the position of the downstream mark x.

Repeat step 5 times.

Write down the room temperature before and after the experiment, and take the average as the temperature t of the water during the measurement.

4 Calculate the surface tension coefficient of water and its uncertainty.

The thickness can be changed by air pressure, and there is no exact value.

The surface tension coefficient of pure water at different temperatures is shown in the table below.

According to the linear relationship between temperature and surface tension coefficient, the surface tension coefficient at 21 degrees Celsius should be .

The surface tension coefficient of liquids is determined by the fact that liquids have a tendency to shrink their surface as much as possible, and we call this force along the surface and shrinking the liquid surface as surface tension. It can be used to explain many phenomena that are unique to substances in a liquid state, such as foam formation, wetting, and capillary phenomena.

The surface tension must be studied in industrial floating hail separation technology and liquid transfer technology.

Experimental principle: The surface tension of the seepage surface of the curved liquid seepage surface is applied to the inside of the liquid along the tangential direction of the liquid surface, and the additional pressure is positive in the case of convex surface, and the additional pressure is negative in the case of concave surface. Both of these conditions are evident in the capillary phenomenon.

When a clean capillary is inserted into the liquid, if the force between the tube wall and the liquid molecules is greater than the force between the liquid molecules, the liquid will stretch along the tube wall, this phenomenon is called infiltration; Conversely, if the liquid does not stretch out on the tube wall, it is called non-wetting.

The capillary is inserted into the water, and the surface of the water rises along the dry wall of the tube cluster due to infiltration. The surface tension shrinks the liquid surface, resulting in a new equilibrium position for the liquid in the tube.

Introduction to the Surface Tension Coefficients of Liquids:

The force that causes the surface of a liquid to shrink is called surface tension. That is, the force between two adjacent parts of the surface of a liquid that pull each other on a unit length. If the liquid surface is divided into two parts by a straight line of length l, the mutual tension f between the two parts is perpendicular to the straight line l and tangent to the surface.

The scale coefficient is the surface tension coefficient of the liquid, which represents the mutual traction force per unit length between two adjacent parts of the liquid surface.

The surface tension coefficient is numerically equal to the surface energy increased when the unit surface area is increased, and the part of the surface internal energy that can be converted into mechanical energy under isothermal conditions is called surface free energy in thermodynamics. From the perspective of energy, the surface tension coefficient is the surface free energy that increases when the unit surface is increased.

Surface tension coefficient of water.

Surface tension of water. where t is the temperature in Celsius and the surface tension is in mn m. This formula works at 10 60.

Capillary phenomenon and surface tension coefficient: the height of the liquid rises and falls in capillary phenomenon. A positive or negative h indicates an upward or downward trend.

The infiltrated liquid rises, and the contact angle is acute; The non-wetting liquid descends, and the contact angle is obtuse.

Methods for determining the surface tension of liquids:

The determination method of liquid surface tension is divided into static method and kinetic method. The static method includes capillary rising method, Du Noüy ring method, Wilhelmy disk method, rotary drop method, hanging drop method, drop volume method, maximum bubble pressure method, and kinetic method includes ** jet method and capillary wave method. Among them, the capillary rise method and the maximum bubble pressure method cannot be used to measure the liquid-liquid interface tension.

The Wilhelmy disc method, the maximum bubble pressure volume force 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 accuracy of the test is not high, and the previous data acquisition and processing methods are not advanced enough, 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 tension coefficient of water is about the same, and of course it is also related to the purity of the water.