Surface tension comparison – mercury vs water at normal temperature At ordinary laboratory conditions, the surface tension of mercury is __________ that of water:

Introduction:
Surface tension governs phenomena such as droplet formation, capillary rise/depression, and wetting. This item checks qualitative knowledge of how mercury compares with water in terms of surface tension at room temperature.

Given Data / Assumptions:

• Temperature near 20–25 °C.
• Clean, uncontaminated surfaces (no surfactants).
• Standard laboratory pressure; gravity effects typical.

Concept / Approach:
Surface tension is the energy per unit area needed to create new surface. Mercury has strong cohesive metallic bonding and poor wetting on glass, leading to a high surface tension and a convex meniscus. Water, while relatively high among common liquids, still has significantly lower surface tension than mercury.

Step-by-Step Solution:
1) Recall qualitative values: water ~ 0.072 N/m at 20 °C; mercury ~ 0.48–0.49 N/m.2) Compare magnitudes: mercury » water.3) Conclude: mercury's surface tension is higher than that of water at normal temperature.

Verification / Alternative check:
Capillary behavior: water rises in clean glass (concave meniscus), while mercury depresses (convex meniscus) because its surface tension is higher and contact angle exceeds 90°, consistent with reduced wetting.

Why Other Options Are Wrong:

• Same as / lower than: contradict benchmark data and observable capillary effects.
• Not comparable / time varying: surface tension is well-defined at given T; no periodic time variation exists in a clean system.

Common Pitfalls:
Confusing density (also higher for mercury) with surface tension; overlooking contamination that can reduce water's surface tension.

Final Answer:
higher than