When grease or oil (non-polar hydrocarbons) are mixed with a soap- water solution, the soap molecules work as a bridge between polar water molecules and non-polar oil molecules. Since soap molecules have both properties of non-polar and polar molecules the soap can act as an emulsifier.

Why is soap an emulsion?

To prevent the oil and water from separating (and thus the food spoiling), soap-like chemicals called emulsifiers are added. ... Hydroxyl groups are hydrophilic and dissolve in water, whilst fatty acid chains are hydrophobic and dissolve in oil, forming a stable emulsion.

How does soap emulsify?

Soap can emulsify fats and oils by forming micelles around oil droplets. The soap molecules surround an oil droplet so that their nonpolar tails are embedded in the oil and their charged “head” groups are on the exterior of the droplets, facing the water.