Emulsifying agents prevent coalescence of droplets. True or false?

• A. True
• B. False
• C. Sometimes
• D. Never

Answer: (A)

Emulsifying agents stabilize droplets by preventing coalescence. They adsorb at the oil–water interface, lowering interfacial tension and forming a protective interfacial film around each droplet. This film provides steric and sometimes electrostatic stabilization, so when droplets collide they are less likely to fuse into larger droplets. Under appropriate conditions (proper type and amount of emulsifier, suitable environment) this greatly reduces coalescence. Do keep in mind that other instability processes, like creaming or Ostwald ripening, can still occur, but they are not coalescence.