Final answer:
Oil and water are immiscible due to the difference in their polarities. The weak attractive forces between water and oil molecules are not strong enough to overcome the stronger hydrogen bonding between water molecules. As a result, oil and water form separate layers when mixed.
Step-by-step explanation:
When oil and water are mixed, they do not form a solution because they are immiscible. Oil is a nonpolar compound, while water is a polar compound. The weak attractive forces between the polar water molecules and the nonpolar oil molecules are not strong enough to overcome the much stronger hydrogen bonding between water molecules.
As a result, oil and water form separate layers, with the less dense oil floating on top of the water. The oil droplets do not dissolve in water but instead form separate droplets or a film.
To separate oil and water once they are mixed, various methods can be used such as gravitational separation, using a separating funnel, or utilizing surfactants to help emulsify the oil and water mixture.