Surface Tension of Liquids Explained

Surface tension is a property of liquids that arises from the cohesive forces between liquid molecules. It's the tendency of liquid surfaces to shrink into the minimum surface area possible. A higher surface tension indicates stronger cohesive forces.

Comparing Intermolecular Forces

The strength of intermolecular forces directly impacts a liquid's surface tension. Let's compare the forces present in the given liquids:

• Water (H₂O): Exhibits strong hydrogen bonding between molecules due to the highly polar O-H bonds. This leads to very strong cohesive forces.
• Ethanol (C₂H₅OH): Also has hydrogen bonding (due to the -OH group), but it is weaker than in water because the nonpolar ethyl group (C₂H₅-) reduces the overall polarity and the extent of hydrogen bonding.
• Methanol (CH₃OH): Possesses hydrogen bonding, similar to ethanol, but is a smaller molecule. While it has H-bonding, water's extensive network is stronger.
• Ethane (C₂H₆): Is a nonpolar molecule. The intermolecular forces are primarily weak London dispersion forces, which are significantly weaker than hydrogen bonds.

Conclusion on Surface Tension

Based on the strength of intermolecular forces:

• Water has the strongest forces (extensive hydrogen bonding).
• Ethanol and Methanol have weaker hydrogen bonding.
• Ethane has the weakest forces (London dispersion).

Therefore, water exhibits the highest surface tension among the listed liquids.