Why is ice less dense than liquid water?

• A. The molecules in ice move faster, causing them to spread out more than in liquid water.
• B. Ice has fewer hydrogen bonds than liquid water, resulting in a lower density.
• C. Hydrogen bonds in ice form a crystalline lattice that spaces water molecules farther apart than in liquid water.
• D. Ice contains more dissolved gases than liquid water, making it less dense.

Answer: (C)

Verified step by step guidance

1. Understand the concept of density: Density is defined as mass per unit volume. If the same mass occupies a larger volume, the substance is less dense.
2. Examine the role of hydrogen bonds: In liquid water, hydrogen bonds are constantly breaking and reforming, allowing water molecules to pack closely together. In ice, hydrogen bonds stabilize into a crystalline lattice structure.
3. Describe the crystalline lattice: The hydrogen bonds in ice arrange water molecules in a hexagonal pattern, creating open spaces between molecules. This increases the volume of ice compared to liquid water.
4. Relate the structure to density: Since ice has a larger volume for the same mass of water molecules, its density is lower than that of liquid water.
5. Conclude why ice floats: The lower density of ice compared to liquid water explains why ice floats on water, an important property for aquatic ecosystems.