Which of the following is a method to improve stability by adjusting the dispersed phase?

• A. Increase particle size
• B. Reduce particle size
• C. Change color
• D. Change shape

Answer: (B)

Finer dispersed-phase particles lead to better stability of a suspension or emulsion. Smaller particles settle or cream much more slowly because settling velocity is proportional to the square of the particle radius (Stokes’ law). So when the dispersed phase is broken into smaller droplets or particles, gravitational separation occurs more slowly, giving the system greater kinetic stability. Additionally, smaller droplets present more surface area that can be effectively coated by stabilizers (surfactants or polymers), which helps prevent flocculation and coalescence. In short, reducing particle size directly slows separation processes and, with proper stabilization, enhances overall stability.