Answer:
The higher-density liquid water shelters organisms from cold air better than the less-dense ice.
Explanation:
Because of this difference in density, the waters of lakes and seas do not freeze completely because a less dense ice layer forms on the surface and creates a natural thermal insulator that makes the water below it remain in the liquid phase. This saves the animal and plant life of lakes and seas.
Ice works as a thermal insulator because its specific heat (2.03 J/g. ºC) is lower than that of water (4.18 J/g. ºC).
After the cold is over and the hot season comes, the surface ice melts easily. But that would not happen if the ice dropped to the bottom of lakes and seas. With this, the animal and plant life would be compromised.
Another important point is that, as already mentioned, liquid water reaches its maximum density at approximately 4ºC, which is 1,000 g/cm3. Therefore, during times such as spring and fall, the water reaches temperatures near this and becomes denser than the rest, going to the bottom. This causes a vertical movement called the convection current, which is responsible for mixing the nutrients dissolved in water.
