Dispersions containing small particles in the 0.5-10 µm range are classified as what type?

• A. Coarse dispersions
• B. Fine dispersions
• C. Ultrafine dispersions
• D. Medium dispersions

Answer: (B)

The size of the dispersed particles determines how we classify dispersions. When the particles are in the range of about 0.5 to 10 micrometers, they’re considered fine dispersions. This sits between the coarser category, which includes particles larger than about 10 µm that settle rapidly, and the ultrafine category, which involves particles smaller than about 0.5 µm that behave more like colloids. The reason this classification matters is that particle size influences how quickly the particles sediment under gravity, how easily the suspension can be redispersed, and its overall stability. Particles in the fine range stay dispersed more readily than coarse ones but are still large enough to settle relatively slowly compared with even bigger particles, making “fine dispersions” the appropriate label for 0.5–10 µm.