In the solid state (ice), what is notable about the positions of water molecules compared to their arrangement in liquid water?

• A. The molecules are packed more closely together than in liquid water, making ice denser.
• B. The molecules form a compact, hexagonal structure that increases density.
• C. The molecules are randomly distributed with no specific pattern.
• D. The molecules are arranged in a regular, open lattice structure, making ice less dense than liquid water.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the structure of water molecules in ice. In the solid state, water molecules form hydrogen bonds that create a regular, open lattice structure. This arrangement is different from the more random and compact arrangement in liquid water.
2. Step 2: Recognize the impact of the lattice structure on density. The open lattice structure in ice creates more space between water molecules compared to the arrangement in liquid water, making ice less dense.
3. Step 3: Compare the density of ice and liquid water. Since ice is less dense, it floats on liquid water, which is a unique property of water compared to most substances.
4. Step 4: Eliminate incorrect options. The molecules in ice are not packed more closely together, nor do they form a compact hexagonal structure that increases density. They are also not randomly distributed.
5. Step 5: Confirm the correct answer. The correct answer is that water molecules in ice are arranged in a regular, open lattice structure, making ice less dense than liquid water.