Final answer:
Surface tension is defined as the energy required to increase a liquid's surface area, measured in J/m² or dyn/cm, with dimensions of energy per unit area. It is numerically equivalent to surface energy, as both signify the energy needed to extend a liquid's surface, reflecting the energy to overcome intermolecular forces.
Step-by-step explanation:
Surface tension is a physical phenomenon observed as the energy required to increase the surface area of a liquid due to the cohesive forces between the molecules at the surface. These cohesive forces cause the surface of a liquid to behave as though it were covered with a stretched membrane. Units and dimensions for surface tension are typically joules per square meter (J/m²), or in the CGS system, dynes per centimeter (dyn/cm), where 1 dyn/cm equals 1×10⁻² N/m.
The concept of surface energy is numerically equal to surface tension because both represent the amount of energy needed to create new surface area or to extend a surface. This equivalence can be shown through the concept that when a liquid surface is extended, molecules are brought from the bulk of the liquid to the surface, increasing the potential energy of the system, which matches the definition of adding surface energy. The required work to increase the surface area is the product of the surface tension and the increase in surface area, which is compatible with the definition of energy (work) consumed in the process.
As an example, in the case of water, with its strong intermolecular hydrogen bonding, the surface tension is high, reflecting the high surface energy required to increase its surface area. Substances with weaker intermolecular forces, like many low-boiling-point organic liquids, will have a lower surface tension and thus require less surface energy to increase their surface area.