Question

11 explain what makes a water molecule polar 12 match the property of water with its description. description answer a. water’s ability to attract other water molecules b. water’s ability to absorb large amounts of thermal energy before its temperature increases c. water’s ability to float as a solid d. water’s ability to attract other polar substances e. water’s ability to dissolve substances property a. universal solvent b. adhesion c. high heat capacity d. cohesion e. density

Explanation:

Question 11

A water molecule ($H_2O$) is polar due to its molecular structure. The oxygen atom is more electronegative than hydrogen atoms, causing the shared electrons in the covalent bonds to be pulled closer to the oxygen. This creates a partial negative charge ($\delta^-$) on the oxygen and partial positive charges ($\delta^+$) on the hydrogens. Also, the bent (angular) shape of the molecule (due to lone pairs on oxygen) means the dipole moments of the two $O - H$ bonds do not cancel out, resulting in a net dipole moment for the molecule.

• a: Cohesion is the attraction between molecules of the same substance (water attracting water), so a matches D.
• b: High heat capacity is water's ability to absorb much thermal energy before temperature rises, so b matches C.
• c: Water as a solid (ice) floats because ice is less dense than liquid water, related to density property, so c matches E.
• d: Adhesion is attraction between water and other polar substances, so d matches B.
• e: Water is a universal solvent as it can dissolve many substances, so e matches A.

Answer:

A water molecule is polar because oxygen is more electronegative than hydrogen, creating partial charges ($\delta^-$ on O, $\delta^+$ on Hs), and its bent shape means dipole moments of $O - H$ bonds do not cancel, giving a net dipole.

Question 12