* Water (H₂O) is a polar molecule. This means it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom, due to the uneven sharing of electrons. This polarity allows water molecules to form strong hydrogen bonds with each other.
* Methylene chloride (CH₂Cl₂) is a non-polar molecule. The carbon and chlorine atoms have similar electronegativity, resulting in an even distribution of charge. This means methylene chloride molecules cannot form strong hydrogen bonds with water molecules.
Like dissolves like: Polar solvents like water dissolve polar solutes, and non-polar solvents like methylene chloride dissolve non-polar solutes. Because of their contrasting polarities, water and methylene chloride are immiscible, meaning they do not mix and form separate layers when combined.
The stronger intermolecular forces between water molecules (hydrogen bonds) are much stronger than the forces between water and methylene chloride molecules, preventing them from mixing.
