When water freezes, it undergoes a phase transition from a liquid to a solid state. This process involves the formation of a crystalline structure as the temperature drops below 0°C (32°F).
Step 2: Molecular Behavior During Freezing
As the temperature decreases, the kinetic energy of water molecules reduces, causing them to move less vigorously. Eventually, the molecules arrange themselves into a fixed, orderly pattern, forming ice.
Step 3: Expansion of Water
Unlike most substances, water expands as it freezes. This is due to the hydrogen bonding in water molecules, which creates an open hexagonal structure in ice, making it less dense than liquid water.
Final Answer
\(\boxed{\text{As water freezes, it begins to expand.}}\)