Why are oil and water immiscible?
Water molecules are polar molecules and form hydrogen bonds with each other. Oil molecules don’t form hydrogen bonds, and without hydrogen bonds the oil molecules can’t bond with the water molecules. Note that soap is essentially a hybrid molecule: one end is a hydrocarbon and bonds to other hydrocarbons, while the other end is a water molecule that is attracted to water. Thus, the hydrocarbon end of the soap molecule “sticks” to grime, while the water end of the molecule allows it to be attracted to the water that is the usual solvent one uses when one uses soap.
