Final answer:
Ethylene glycol (HOCH2CH2OH) has the highest surface tension among the given options due to its ability to form multiple hydrogen bonds, which are stronger intermolecular forces than those present in other listed substances.
Step-by-step explanation:
To determine the substance with the highest surface tension, we must examine the intermolecular forces present in each. Surface tension is a measure of the energy required to increase the surface area of a liquid, and is related to the strength of the intermolecular forces within the liquid. The options provided are CH2Cl2 (dichloromethane), HOCH2CH2OH (ethylene glycol), CH3CH2CH2CH3 (butane), CH3CH2Br (ethyl bromide), and CH3CH2CH2OH (propanol).
Based on our knowledge of intermolecular forces, we know that hydrogen bonding is generally stronger than dipole-dipole interactions and London dispersion forces. Among these molecules, ethylene glycol is able to form multiple hydrogen bonds due to the presence of two hydroxyl groups, which imparts it with a higher surface tension in comparison to the others. Therefore, out of the given options, HOCH2CH2OH (ethylene glycol) has the highest surface tension because of its capability to establish strong hydrogen bonds.