Step 1: Understanding the Concept:
Surface tension arises from the imbalance of intermolecular attractive forces on molecules sitting at a liquid's surface. Liquids with stronger cohesive forces, such as hydrogen bonding, resist surface expansion more and show higher surface tension.
Step 2: Key Formula or Approach:
Rank each liquid by the strongest type of intermolecular force present in it: weak dispersion forces sit at the bottom, and hydrogen bonding or strong dipole interactions sit at the top of that ranking.
Step 3: Detailed Explanation:
Octane and carbon tetrachloride are both non-polar, held together only by weak London dispersion forces, giving them comparatively low surface tension values. Oleic acid carries a carboxylic acid group capable of forming hydrogen bonds between neighboring molecules, giving it noticeably stronger surface cohesion than either of these simple hydrocarbons. Mercury behaves differently altogether, since its cohesion comes from metallic bonding between mercury atoms rather than from molecular intermolecular forces, which sets it apart as a distinct class of liquid. Comparing the molecular liquids on the same footing, the hydrogen-bonding oleic acid shows the strongest surface cohesion of the group.
Step 4: Final Answer:
Oleic acid has the highest surface tension among these liquids.