Question

Explain the following:
Fish survive in ponds even when the atmospheric temperature is below $0^{o}C$.

Answer 1

During colder weather, the aquatic life is preserved by the anomalous expansion of water. The topmost layer in the pond contracts when the temperature drops, hence becomes denser and sinks to the bottom. Until the water touches maximum density at $4^{o}C$, the circulation set up. Drop in temperature cause the top ;ayer to expand and remain at the top till it freezes. Hence though the upper layer is frozen, the water at the base is at ${45}^{o}C$, hence the fishes an easily survive.