Which property explains why droplets bead up on a non-wetting surface?

Which property explains why droplets bead up on a non-wetting surface?

• A. Surface tension
• B. Adhesion
• C. Viscosity
• D. Density

Answer: (A)

Droplets bead up on a non-wetting surface because the cohesive force at the liquid’s surface, called surface tension, acts to minimize the surface area of the liquid. When adhesion to the surface is weak, the liquid doesn’t spread out much, so the surface tension pulls the liquid into a compact shape—roughly a sphere—leading to a bead-like appearance. Viscosity affects how quickly the droplet can change shape, but not whether it beads up. Density influences weight but not the spreading behavior; gravity plays a smaller role than surface forces for typical droplet sizes on non-wetting surfaces.

Droplets bead up on a non-wetting surface because the cohesive force at the liquid’s surface, called surface tension, acts to minimize the surface area of the liquid. When adhesion to the surface is weak, the liquid doesn’t spread out much, so the surface tension pulls the liquid into a compact shape—roughly a sphere—leading to a bead-like appearance. Viscosity affects how quickly the droplet can change shape, but not whether it beads up. Density influences weight but not the spreading behavior; gravity plays a smaller role than surface forces for typical droplet sizes on non-wetting surfaces.