Electronegativity and Polarity: Why Oil and Water

Don’t Mix

• Water molecules are polar; the molecules that compose oil are generally nonpolar.
• Polar molecules interact strongly with other polar molecules because the positive end of one molecule is attracted to the negative end of another, just as the south pole of a magnet is attracted to the north pole of another magnet.
• A mixture of polar and nonpolar molecules is similar to a mixture of small magnetic and nonmagnetic particles. The magnetic particles clump together, excluding the nonmagnetic ones and separating into distinct regions. Similarly, the polar water molecules attract one another, forming regions from which the nonpolar oil molecules
• are excluded.