Question

Ice floats in the water.Explain.

Answer 1

As the temperature drops, the molecule will tend to move more closer, which results in the decrease in the volume. And hence increases the density. In water, at ${{4}^{0}}C$ the molecules suddenly start to expand till${{0}^{0}}C$results in the decrease of density.

Complete answer:
Water- it is known as the elixir of life. The reason behind this is that the life of every living organism depends on water. Even the two-third part of our planet Earth is covered with water. It helps to complete all the metabolic activities of living organisms.
Water has so many amazing properties which help to sustain life on the Earth such as its specific heat capacity, latent heat of fusion, vaporization etc. We are discussing one such property. It is the abnormal expansion of water. As you know, water can be seen in three different states of matter. That is in solid, liquid and gaseous state.
In the gaseous state, the molecules are loosely packed, which means they occupy more space. As the volume increases, the density decreases. Thus the gaseous state is less dense compared to liquid and solid-state. Then the liquid, its density ranges between solid and gas. And solids are highly compact. So as we come from the gas to liquid and liquid to solid, it is seen that the density increases continuously. But there is a contradiction to this in the case of water.
In the case of water, the density increases as the temperature starts to drop. But at ${{4}^{0}}C$, the water molecules begin to expand till ${{0}^{0}}C$. This results in a decrease of the density of water. So the maximum density of water is obtained at ${{4}^{0}}C$. It is$1{g}/{{{m}^{3}}}\;$. That is why the ice floats in the water. At ${{0}^{0}}C$, the density of ice is $0.93{g}/{{{m}^{3}}}\;$. That is why the ice floats in the water due to buoyancy.
This is a blessing for the aquatic organisms. In the winter season, in lakes and rivers as the temperature drops, only the water on the upper layer freezes. And the water at the bottom does not freeze and stays at ${{4}^{0}}C$throughout the season. Since ice is less dense, it will float on the water, acting like a protective layer. Thus aquatic life is preserved during the winter season.

Note:
Hydrogen in the water molecule is responsible for this abnormal expansion. They keep the molecules away at a greater distance below ${{4}^{0}}C$ compared to a higher degree. Since the density of water is unity at${{4}^{0}}C$, it is used as a reference to find the specific gravity of other substances.