Solubility and Polarity
* "Like dissolves like": A general rule in chemistry is that substances with similar polarities dissolve well in each other.
* Polarity: A molecule is considered polar if it has an uneven distribution of electrical charge. One end of the molecule is slightly positive, and the other end is slightly negative.
* Water (H₂O) is polar: The oxygen atom in water is more electronegative than the hydrogen atoms, creating a partial negative charge on the oxygen side and partial positive charges on the hydrogen side.
* Sodium chloride (NaCl) is ionic: The strong attraction between the positively charged sodium ions (Na+) and negatively charged chloride ions (Cl-) forms a crystal lattice. When NaCl dissolves, the water molecules surround the ions and pull them apart, breaking the ionic bonds. This process is called hydration.
Why NaCl is not soluble in gasoline
* Gasoline is nonpolar: Gasoline is primarily composed of hydrocarbons, which are molecules with carbon and hydrogen atoms. These molecules are very symmetrical and share electrons evenly, making them nonpolar.
* NaCl is ionic and polar: Since gasoline is nonpolar, it cannot effectively interact with the charged ions in NaCl. The attraction between the nonpolar gasoline molecules and the ionic NaCl molecules is very weak, so NaCl does not dissolve.
In summary: Water's polarity allows it to break down the ionic bonds in NaCl and form strong attractions with the ions. Gasoline, being nonpolar, cannot effectively interact with the charged ions, so NaCl does not dissolve in it.
