Interfacial tension is the force per unit length acting at the interface between two immiscible phases, such as a liquid and a gas or two different liquids (oil and water). It arises due to the imbalance of cohesive and adhesive forces at the molecular level, causing the interface to behave like a stretched elastic membrane. It quantifies the energy required to increase the surface area of the interface. For example, it’s why water forms droplets on a waxed surface or why soap reduces the surface tension of water, making it spread more easily.
Interfacial tension phases are distinct, immiscible substances or states of matter (solid, liquid, gas) that meet at an interface where interfacial tension occurs. Interfacial tension arises due to differences in molecular interactions (cohesive within each phase, adhesive between phases) at these interfaces, driving the system to minimize surface energy. The specific phase combination dictates the magnitude and behavior of the interfacial tension. These phases are typically:
Liquid-Liquid - The interface between two immiscible liquids, like oil and water, where interfacial tension governs behaviors like droplet formation or emulsion stability.
Liquid-Gas - The interface between a liquid and a gas (water and air), often referred to as surface tension when the gas is air, affecting phenomena like capillary action or bubble formation.
Liquid-Solid - The interface between a liquid and a solid, influencing wetting behavior (water on glass vs. wax), where interfacial tension determines whether the liquid spreads or beads.
Solid-Gas - The interface between a solid and a gas, relevant in processes like adsorption or surface energy studies.
Solid-Solid - The interface between two solids, less common but relevant in material science for grain boundaries or adhesion.
