Question

what do you understand by the anomalous expansion of water ?

Answer 1

Anomalous expansion of water: water has a unique property of anomalous expansion. When water is cooled from room temperature it first contracts in volume and becomes increasingly dense as do other liquids, but at 4° C water reaches its maximum density.

Answer 2

When temperature decreases, water contracts and it becomes denser. But decreasing from 0 to 4 °C, it abnormally expands and becomes less dense. This is called anomalous expansion.