Chemistry Regents Practice Test

What is the polarity of water compared to methane (CH4)?

1. More polar

2. Less polar

3. Identical

4. Nonpolar

The correct answer is: More polar

The polarity of water is significantly higher than that of methane due to the differences in their molecular structures and the electronegativity of the atoms involved. Water (H2O) is a bent molecule where the oxygen atom is more electronegative than the hydrogen atoms. This causes a partial negative charge on the oxygen and partial positive charges on the hydrogens, leading to a dipole moment. The uneven distribution of electron density creates a polar molecule with distinctive positive and negative ends. In contrast, methane (CH4) is a tetrahedral molecule with carbon at the center and hydrogen atoms arranged around it. The electronegativity difference between carbon and hydrogen is relatively small, resulting in a nonpolar molecule as the individual bond dipoles cancel each other out. Therefore, because of the bent shape of water and the significant difference in electronegativities, water is more polar compared to methane, which is nonpolar. This key difference in polarity affects their physical properties, such as solubility and boiling points, and plays an essential role in biological systems and various chemical reactions.