The magnitude of surface tension of liquid depends on the attractive forces between the molecules. Arrange the following in increasing order of surface tension:

Water, alcohol (C2H5OH) and hexane [CH3(CH2)4CH3].

In the above given molecules, only hexane (CH3(CH2)4CH3) is a non-polar molecule in which Landon dispersion forces exist. These forces are very weak while both water and alcohol are polar molecules in which dipole-dipole interactions as well as H-bonding exists.
However, H-bonding interactions are much stronger in water than H2O, therefore, it possesses stronger intermolecules than alcohol and hexane. Hence, the increasing order of surface tension is
hexane < alcohol < water
Greater is the attractive forces between the molecules, greater is the magnitude of surface tension of liquid.