Question

Explain how the anomalous expansion of water plays a major role in the sustenance of aquatic life in cold places? [3 MARKS]

Answer 1

Explanation: 3 Marks

Normal behavior for a liquid is to expand on heating and contract on cooling. A liquid that contracts is said to become more dense.
Water behaves like a normal liquid when it's cooled down to 4 deg i.e it contracts, but when cooled further down from 4deg to 0 deg, it behaves anomolusly i.e it expands instead of contracting further. So ice at 0 deg is less dense than water at 4 deg.

When a lake starts getting cold, the water at the top hits 4 degrees becomes dense and sinks to the bottom, this keeps happening until all water in the lake has reached 4 deg celcius. Now, when the temperature outside drops further, and the water at the top falls to 0 degree celcius, the surface turns to ice. But ice at the top is less dense than the water at the bottom. Hence, it does not sink, so much so that even when you see a lake frozen at the top, the water below is still reamins at an even temperature at 4 degrees where aquatic life can survive. This is how the anomalous expansion of water plays a major role in the sustenance of aquatic life in cold places.