To put it simply, surface tension can be defined as the tendency of liquids to shrink to avail the minimum surface area possible. This is caused by the attraction between each molecule of the liquid, which wants to stay together and reduce the space between each other.

This force of attraction is also true for liquids interacting with gases or solids. In fact, this is the reason that water tends to stick to the sides of a beaker even when poured out. Or oil forming a film on the surface of the water. 

Surface Tension

Surface tension is a feature of liquids that is influenced by intermolecular interactions and is derived from the cohesive forces that exist between molecules in a liquid. According to thermodynamics, systems like paints and inks attempt to achieve a state with the greatest number of beneficial interactions. This means that liquids will take on a structure in which the number of bulk molecules is maximized and the number of surface molecules is minimized.

Surface molecules are partially naked since they are not completely surrounded by their peers at the liquid’s surface. When compared to molecules in the bulk of the liquid, molecules near the liquid-air interface have less favorable interactions and are in a higher energy state. As a result, energy is required to transfer molecules from the liquid’s bulk to the surface. The more energy it takes to expand a liquid’s surface area, the stronger the interactions between the molecules.

The surface tension of water

The International Association for the Properties of Water and Steam (IAPWS) has calculated the surface tension of pure liquid water in contact with its vapor as:

w = 235.8 (1-T/TC)1.256[1-0.625 (1-T/TC)mN/m,

Temperature T and the critical temperature TC = 647.096 K are both given in kelvins. From the triple point (0.01 °C) through the critical point, the complete vapor-liquid saturation curve is valid. 

Surface tension examples

• Walking on water: Because their weight is insufficient to penetrate the surface, little insects like the water strider may walk on water.
• Floating a needle: Even though it is several times as dense as water, a precisely placed little needle may be made to float on the surface of the water. The needle will descend quickly if the surface is disturbed to break up the surface tension.
• Don’t get your hands on the tent! : The surface tension of water will bridge the pores of finely woven tent fabrics, making them slightly rainproof. However, if you press your finger on the tent material, the surface tension is broken, and rain will trickle through.

1. The surface tension and its application in our daily life:

• On the surface of water, small insects like water striders can walk because their weight is very less and that’s why they are not able to penetrate the water. 

• Based on surface tension, detergents and soaps also work. They reduce the water’s surface tension so that the detergents and soaps can effortlessly soak into the holes and pores.

• The surface tension of water provides the tension to shape the bubble with water and this is the reason why the water bubbles are round, and the surface tension also minimizes the bubble to form spherical shapes.

• On the surface of the water, a small needle can be floated.

2. The application of surface tension on human beings health:

• Several types of diseases can be determined by the human body due to the surface tension changing into biological phenomena.

3. The application of surface tension in the Industrial processes.

In industrial processes, surface tension is a very crucial factor.  

• The R&D departments use the surface tension phenomena in all the industrial plants for improving the quality of products.

• With the help of better biological surfactants at a lower temperature the cleaning properties can be improved by the use of detergent formulations.

4. The application of surface tension in pharmaceutical science:

• On the surface of the molecule, drugs like bioavailability, chemical activity, dissolution, and absorption are dependent.

• In today’s world, the knowledge and understanding of surface tension are very important for developing new and better-performing products.

5. The application of surface tension is extremely crucial in food and packaging products also. 

Interfacial tension

It is very much related to the surface tension. In the interfacial tension, the cohesive forces are also included. Between the liquid stage of one substance or the gas or liquid stage of another substance, the major forces are adhesive forces (tension) included in the interfacial tension. 

Application of Interfacial tension. 

In many procedures and phenomena where various phases touch one another, a very important role is played by the interfacial tension. 

• With the reduction in the interfacial tension of water the aging of hydrophobic liquid frequently goes hand in hand. 

Measurements of the interfacial tension is a crucial quality test in cases like these for instance transformer oil. 

• The interfacial tension affects the long-term stability of interface contact in the case of the solid-liquid phase boundaries. For instance, coating processes with gluing. 

Conclusion:

Surface tension is the phenomenon that arises when the surface of a liquid is in touch with another phase, it is explained as per the definition of surface tension. Based on surface tension detergents and soaps also work. So, they reduce the water’s surface tension so that the detergents and soaps can effortlessly soak into the holes and pores. Between the liquid stage of one substance or the gas or liquid stage of another substance, the major forces are adhesive forces (tension) included in the interfacial tension. When by the surfactants the Interfacial tension is reduced, then after flooding with water the organic phase can be mobilized.