What happens to the hexagonal open structure of ice when sufficient pressure is applied to it?

• A. The hexagonal structure becomes more open and less dense.
• B. The structure collapses and ice transforms into a denser phase.
• C. The hexagonal structure remains unchanged regardless of pressure.
• D. Ice melts directly into water without any structural change.

Answer: (B)

Verified step by step guidance

1. Understand the nature of the hexagonal open structure of ice, known as ice Ih, which is characterized by a lattice arrangement that creates an open, less dense structure compared to liquid water.
2. Recognize that applying sufficient pressure to ice Ih affects the hydrogen bonding network and the arrangement of water molecules in the crystal lattice.
3. Recall that under high pressure, the hexagonal structure of ice Ih cannot maintain its open framework and undergoes a phase transition to a denser crystalline form, such as ice II, ice III, or other high-pressure ice phases.
4. Note that this phase transition involves the collapse of the open hexagonal structure, resulting in a more compact arrangement of molecules and an increase in density.
5. Conclude that the correct description is that the hexagonal structure collapses and ice transforms into a denser phase under sufficient pressure, rather than becoming more open, remaining unchanged, or melting directly.