Why ice floats on water?

 

The most wondering affect about ice is that whenever ice is put on water it floats on the surface of the water instead of drowning down. Nevertheless, ice molecules posses same chemical bonding and molecular formula like water molecules it only differs in physical state. Moreover, not only the little pieces of ice like ice cubes floats on water but the massive bergs also show the same phenomenon. The main reason behind this miracle fact is multi-fold and discussed in this article with logical reasons.

Role of density in floating or drowning of objects:  

Density is the pre-eminent factor that decides whether an object can float on water or it will sink down to the bottom. Usually, the objects of low density possess less weight that permits these to float on the surface of water. In contrast, the objects with high density show significantly different behavior owing to high weight. For instance, a piece of paper having 2 × 2 width and length will easily floats on water but paradoxically to it a tiny piece of stone will suddenly sinks down to the bottom due to high density. High density objects can easily displace the weight of water.

Density of ice VS water:

At 0^oC when water is converted from liquid to solid phase in the form of ice its density decreases fundamentally in contrast to other liquids whose density increases on converting in solid form. Density of ice is 9 percent lower than liquid water. The main contributing factor behind this phenomenon is the structure of ice with enough empty spaces. Due to empty spaces among the ice molecules it expands more than water and covers more area. These empty spaces make the ice less dense than liquid water.   

Structure of ice:

Water molecules possess strong covalent bonds along with weaker hydrogen bonding due to attraction between positively charged hydrogen atoms of one molecule with negatively charged oxygen atom of the other water molecule. When water is cooled down below 4^oC the kinetic energy of the system decreases and it becomes difficult for molecules to move or breakage and formation of bond among each other. Consequently, these molecules form more hydrogen bonds and aligned in a hexagonal structure with significant empty spaces in the middle. Figure 1 shows the conversion of water from liquid phase to solid phase and difference between the structure of water and ice.

Applications of this phenomenon:

This phenomenon protects marine life in harsh conditions of winter as ice always freezes from surface to bottom. As a consequence, the upper layer of ice on the surface of the water serves as an insulator and does not allow the inner water to cool easily. It provides the marine life underneath lakes and glaciers to survive in winter comfortably.

Figure. 1. Difference between structure of water and ice 

Related questions

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