Cohesive versus free-flowing bulk solids: identify the cohesive material among the following common bulk solids.

Introduction / Context:Flow behavior of bulk solids dictates hopper design and conveyor selection. Cohesive materials exhibit interparticle attraction (moisture, plasticity), tending to arch, rat-hole, or smear.

Concept / Approach:Wet clay has strong cohesion due to moisture and plate-like particles; it deforms plastically and tends to stick. Wheat (granular) and dry sand (rounded angular grains) are comparatively free-flowing, exhibiting low cohesion in properly conditioned moisture ranges.

Final Answer:Wet clay