Hexane is an organic solvent that has a density of 0.6603g/cm3 at 20c if hexane is mixed with water there is separation of the two solvents into tie layers why did this seperation occur? which solvent would be on top

When Hexane is mixed with Water it forms a immiscible mixture. The two solvents does't make a uniform solution and create two layers.

Explanation:
                    Hexane is chain of six carbon atoms attached to carbon and hydrogen atoms. The molecule of hexane is non polar in nature. While water molecule is polar in nature. As LIKE DISSOLVES LIKE, so the hexane solvent being hydrophobic in nature fails to interact with hydrophilic water molecules.

The density of water is 1 g/cm³, it is heavier than Hexane with 0.66 g/cm³, so water will make the bottom layer while hexane will float on water forming the upper layer.