If a liquid has weak cohesive bonds, what is likely to happen on another material?

• A. Liquids with weak cohesive bonds tend to spread over the surface.
• B. Bead up into droplets.
• C. Evaporate instantly.
• D. Sink into surface.

Answer: (B)

When a liquid sits on a solid, whether it spreads out or stays as beads depends on the balance between cohesion (how strongly the liquid molecules stick to each other) and adhesion (how strongly the liquid sticks to the surface). If the cohesive forces within the liquid are weak, the molecules aren’t strongly attracted to one another, so they’re less likely to pull together into a thin, spreading film. Instead, the liquid tends to gather into small clusters that minimize contact with the surface and stay as droplets. That’s why a liquid with weak cohesive bonds is likely to bead up into droplets on another material.

The other outcomes—spreading into a film, evaporating instantly, or sinking into the surface—would require different relationships between cohesion and adhesion than what’s described here.