<h2> <u> ANSWER</u></h2><h2><u /></h2><h3>Explanation:</h3>
From 0° to 4° water contracts so its density increases. Above 4°C, water exhibits the expected expansion with increasing temperature. The density of water reaches its maximum value of 1000 kg/m³ at 4°C.
We can use this unusual thermal expansion behavior of water why a pond freezes slowly from the top down. When the atmospheric temperature drops from 7°C to 6°C ,say the water at the surface of the pond also cool and consequently decreases in volume. This means the surface water is more dense than the water below it, which is not yet cooled nor decrease in volume. As a result, the surface water sinks and warmer water from below is forced to the surface to be cooled, a process called Upwelling. When the atmospheric temperature is between 4°C and , however, the surface water suspends as it cools, become less than the water below it. The sinking process stops and eventually the surface water freezes. As the water freezes, the ice remains on the surface because ice is less dense than water. The ice continues to build up on the surface, and water near the bottom of pond remains at 4°C. Further, the ice forms an insulating layer that slows heat loss from the underlying water, offering thermal protection for marine life.
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