Absorbed Film and Interfacial Tension Theory describes the role of a film at the interface in stabilizing emulsions. Which statement best reflects this theory?

• A. ALL statements are correct
• B. Only ONE statement is correct
• C. TWO statements are correct
• D. THREE statements are correct

Answer: (A)

This theory is about how an adsorbed film at the interface lowers the energy barrier to forming and maintaining emulsions. When emulsifier molecules accumulate at the oil–water (or air–water) interface, they form a film that reduces interfacial tension. This lower tension means the interface is less prone to drastic changes in area, and it also helps droplets resist disruption.

Beyond simply lowering tension, the film acts as a physical barrier between droplets. Its thickness, elasticity, and viscosity determine how easily the thin liquid film between approaching droplets drains and stabilizes. A robust, viscoelastic, or sterically stabilized film makes coalescence less likely, so droplets stay separate longer. The specific properties of the film—how strongly the emulsifier adsorbs, the film’s rigidity or deformability, and any additional electrostatic or steric repulsion—all contribute to emulsion stability.

Because the theory describes multiple, compatible roles of the interfacial film—lowering interfacial tension, creating a barrier to coalescence, and providing protection through its mechanical properties—it's consistent for all these aspects to be correct. That’s why selecting the statement that all statements are correct best reflects the theory.