• id: JME-10-N06
• title: Water's Anomalous Behavior (0-4 degrees C)
• tags: water, anomalous, density-maximum

Water has maximum density at 4 degrees C (999.97 kg/m$^3$). Between 0 and 4 degrees C, water contracts upon heating (anomalous — negative $\gamma$). Above 4 degrees C, it expands normally. Biological significance: in winter, lake surfaces freeze first (ice at 0 degrees C floats), while the bottom remains at 4 degrees C (densest), allowing aquatic life to survive. The anomaly is due to hydrogen bonding — the open hexagonal structure of ice persists partially in cold water, making it less dense.