The liquids hexane and water are placed in a test tube. the test tube is stoppered, shaken, and placed in a test tube rack. the liquids separate
into two distinct layers because hexane and water have different
(1) formula masses
(2) molecular polarities
(3) ph values
(4) specific heats

Answer is: (2) molecular polarities.

Hexane is alkane (acyclic saturated hydrocarbon, carbon-carbon bonds are single) of six carbon atoms.

Hexane (C₆H₁₄) is nonpolar molecule.

Water (H₂O) is polar molecule.

Bonds between oxygen and hydrogen atoms are polar covalent chemical bonds.

Water is polar because of the bent shape of the molecule.  

Oxygen atom in water molecule has sp3 hybridization. The bond angle between the two hydrogen atoms is approximately 104.45°.