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Updated on 06th February, 2023 , 6 min read
The phenomenon of surface tension happens when the surface of a liquid comes into contact with another fluid (it can be a liquid as well). Surface tension is the propensity of fluid surfaces to contract into the smallest feasible surface area.Liquids have the lowest surface area imaginable. The liquid's surface acts like an elastic sheet. Surface tension is determined not only by the forces of attraction between particles inside a specific liquid but also by the forces of attraction of solids, liquids, and gases in contact with it. Surface tension energy may be thought of as being roughly similar to the effort or energy necessary to remove the surface layer of molecules in a unit area.
Surface tension is commonly measured in dyn/cm, which is the force necessary to break a 1-centimeter film. Surface tension is the attractive force inherent in liquids that pulls surface molecules into the remainder of the liquid. It also reduces the surface area. The attracting forces are caused by electrostatic forces. This cohesiveness is usually referred to at the gas-liquid interface; remember, not liquid-solid or liquid-liquid. One can perceive electrostatic forces, which pull molecules together. The small dipole in water is capable of attracting molecules, particularly to each other. As a result, it is possible to form a tight-knit cohesive unit.
When in a liquid condition, the force has little effect since each molecule pushes in all directions towards the other molecules. However, because there are no molecules to draw the others up, the molecules do not pull up at all on the liquid's surface. A strong force between the molecules pulls them down. As a result, it forms a solid barrier at the liquid-gas boundary. As a result, breaking through the liquid's surface will take far more force than traveling through a liquid.
The surface tension of several liquids is shown in the table below-
Surface Tension (N/m) |
Liquids |
0.072 |
Water |
0.16 |
Helium |
114 |
Sodium Chloride |
2.4 |
Hydrogen |
22.0 |
Ethanol |
The definition of surface tension states that the surface tension is primarily determined by the forces of attraction between the particles inside the provided liquid as well as the gas, solid, or liquid in contact with it.
The liquid particles are drawn together by intermolecular interactions such as the Van der Waals force. The particles are drawn towards the remainder of the liquid along the surface. Surface tension is defined as follows-
Surface Tension is measured in Newton per Meter (N/m) in the SI system. Check out the other units in the table below-
CGS Unit |
dyn/cm |
SI Unit |
N/m |
Surface tension is defined as the ratio of the surface force F acting on a liquid to the length d along which the force operates. This is the same principle that allows insects like water striders to walk on water or a paperclip to float.
As a result, the surface tension formula is-
Surface tension = (surface force/surface tension) (length force acts). |
where,
The surface tension is provided by the formula,
We know that F = ma, so we can solve the problem by inserting the value, we get
By equating the essential quantities in the equation, we get
Further, by solving,
The following are some surface tension examples-
The following is an example of how to use the formula to calculate surface tension-
Ans. F = 7 N
L = 2 m
According to the Formula,
T = F/L
T = 7/2
T = 3.5 N/m
Answer- The F is 0.1 N and the d is 1 cm.
Using the method, we can calculate surface tension-
γ= F /d
γ= 0.1N/1 cm
0.1 N/ 0.01
m = 10 N/m.
Therefore, the surface tension is 10 N/m.
The following are some surface tension measuring techniques:
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