The unique structure of water molecules, with their bent shape and polar nature, allows for strong hydrogen bonding between them. This results in a decrease in density when water is cooled below 4°C, causing it to expand instead of contracting like most substances.
One major implication is that ice is less dense than liquid water, causing it to float on top of bodies of water. This allows for the formation of a layer of insulating ice on top of lakes and oceans, protecting the life forms below from extreme temperatures.
The expansion of ice on top of bodies of water creates a relatively stable and insulated environment for aquatic life to thrive in. This also prevents the water from freezing completely, allowing for life to continue even in cold temperatures.
Other substances with hydrogen bonding, such as silicon, germanium, and gallium, also exhibit anomalous expansion. However, the extent of this phenomenon is not as significant as in water.
The fact that ice floats on top of water is crucial for many natural processes, such as the circulation of nutrients in bodies of water and the protection of marine life during freezing temperatures. It also has practical applications, such as preventing pipes from bursting when water freezes inside them.