Which statement about sedimentation is true?

Which statement about sedimentation is true?

• A. Sedimentation Increases With Smaller Particle Size
• B. Sedimentation Is Independent Of Viscosity
• C. Sedimentation Is Decreased By Reducing Particle Size And Increasing Viscosity
• D. Sedimentation Is Prevented Entirely By Agitation

Answer: (D)

Sedimentation rate in suspensions follows the idea that larger particles settle faster and a more viscous medium slows settling. For small spheres, the settling velocity is proportional to the square of the radius and inversely proportional to viscosity, plus the density difference between particle and liquid. So reducing particle size and increasing viscosity both act to slow or decrease sedimentation. The statement about completely preventing sedimentation with agitation is too absolute—stirring can keep particles suspended, but it doesn’t guarantee no sedimentation under all conditions.

Sedimentation rate in suspensions follows the idea that larger particles settle faster and a more viscous medium slows settling. For small spheres, the settling velocity is proportional to the square of the radius and inversely proportional to viscosity, plus the density difference between particle and liquid. So reducing particle size and increasing viscosity both act to slow or decrease sedimentation. The statement about completely preventing sedimentation with agitation is too absolute—stirring can keep particles suspended, but it doesn’t guarantee no sedimentation under all conditions.