By what percentage does water increase when it is frozen?

When water freezes, it undergoes a unique expansion due to the molecular structure of ice. Water molecules are held together by hydrogen bonds, which arrange themselves into a crystalline lattice when the water transitions from a liquid to a solid state. This structure takes up more space than the liquid form, leading to an increase in volume.

The increase in volume when water freezes is approximately 9%. This expansion is significant because it is one of the reasons why ice floats on water; the density of ice is less than that of liquid water. Understanding this property of water is crucial for various natural processes and ecosystems, particularly in aquatic environments where ice formation affects habitats and climate.

The other percentage options do not accurately reflect the physical properties of water when it freezes. Knowing that the correct answer is 9% helps reinforce knowledge of this phenomenon and its implications in environmental science.