Explanation:
When a liquid is in contact with a solid, the molecules at the surface of the liquid are attracted to the solid surface. However, the molecules in the interior of the liquid experience forces of attraction from all sides, which results in a net force of zero. As a result, the surface molecules have a higher potential energy than the molecules in the interior.

This difference in potential energy leads to the formation of a surface tension, which is a measure of the force required to break or stretch the surface of a liquid. The surface tension tends to contract the free surface of a liquid to the smallest possible area. This can be observed in the behavior of water droplets, which tend to form into spheres due to the surface tension.

Factors affecting surface tension:
Surface tension depends on several factors, including:

1. Nature of the liquid: The surface tension of a liquid depends on its composition and molecular structure. For example, water has a higher surface tension than most organic solvents due to its strong hydrogen bonding.

2. Temperature: Surface tension decreases with increasing temperature, as the thermal energy of the molecules overcomes the forces of attraction between them.

3. Presence of impurities: Surface tension is reduced by the presence of impurities, as they disrupt the bonding between the surface molecules.

4. Pressure: Surface tension increases with increasing pressure, as the molecules are forced closer together.

Applications of surface tension:
Surface tension has several practical applications, including:

1. Capillary action: Surface tension allows liquids to rise up narrow tubes, such as in a glass capillary or a plant stem.

2. Bubble formation: Surface tension plays a key role in the formation of bubbles, which are important in many industrial processes, such as fermentation and wastewater treatment.

3. Wetting and adhesion: Surface tension determines how well a liquid wets a solid surface, and is important in many applications, such as painting and printing.

4. Insect locomotion: Some insects are able to walk on water due to the high surface tension of water.