Which statement helps to explain why ice is less dense than liquid water?

• A. The kinetic energy of water molecules is higher in ice than in liquid water.
• B. Hydrogen bonds in liquid water force the molecules farther apart than in ice.
• C. Ice contains more water molecules per unit volume than liquid water.
• D. In ice, water molecules form an open hexagonal structure due to hydrogen bonding, increasing the volume.

Answer: (D)

Verified step by step guidance

1. Understand that density is defined as mass per unit volume, \(\rho = \frac{m}{V}\), so if the volume increases while mass remains constant, density decreases.
2. Recall that water molecules are held together by hydrogen bonds, which influence the arrangement of molecules in both liquid water and ice.
3. Recognize that in liquid water, hydrogen bonds are constantly breaking and reforming, allowing molecules to be closer together, resulting in a higher density.
4. In ice, water molecules form a rigid, open hexagonal lattice structure stabilized by hydrogen bonds, which creates more space between molecules and increases the volume.
5. Conclude that because ice has a larger volume for the same mass of water molecules, its density is lower than that of liquid water, explaining why ice floats.