Wetting behavior of mercury on glass: Mercury does not wet glass primarily because of which liquid property?

Introduction / Context:Wetting depends on the balance between intermolecular attraction within the liquid (cohesion) and attraction between the liquid and a solid surface (adhesion). Whether a liquid spreads on a surface is determined by this balance along with surface tension and contact angle criteria.

Given Data / Assumptions:

• Clean glass surface and pure mercury.
• Ambient conditions where mercury forms a convex meniscus.
• No chemical reactions at the interface.

Concept / Approach:Mercury exhibits very strong cohesive forces between its own molecules compared with its adhesive attraction to glass. As a result, the contact angle exceeds 90 degrees (non-wetting), and mercury pulls into drops rather than spreading. While surface tension is high, the decisive comparison is cohesion > adhesion.

Step-by-Step Solution:

Verification / Alternative check:Water on clean glass wets (concave meniscus) because adhesion (water–glass) > cohesion (water–water). Mercury is the opposite case.

Why Other Options Are Wrong:

• Adhesion: If adhesion dominated, mercury would wet glass.
• Viscosity: Affects flow resistance, not equilibrium wetting.
• Surface tension alone: High surface tension contributes, but the wetting decision hinges on cohesion vs adhesion balance.

Common Pitfalls:Attributing non-wetting solely to “surface tension” without comparing cohesion and adhesion; ignoring contamination that can alter contact angle.

Final Answer:cohesion