Wondering Why?

Why does Ice float?

Why does Ice float?

In nature, any object floats if it is less dense and occupies less weight per unit volume than the other objects in the water. When you throw a stone into the water it sinks. This happens because the stone has more weight, and hence, displaces the water and sinks to the bottom. If an object floats, then it has to displace the amount of water equal to its weight.

As it cools, water become denser, at four degrees Centigrade. Water expands when it turns into ice, and becomes less dense too. There is an anomalous expansion of water observed at four degrees Celsius. But at 0 degrees Celsius the same mass of water occupies more volume of ice. Therefore, ice becomes less dense. The crystalline arrangement of molecules makes the ice accommodate open spaces in between the water molecules. Due to these spaces, ice becomes less dense, and floats on liquid water.

Ice floats on water, and that is the reason why, with the change in temperature of the underlying water, many animals are able to survive underneath it. Otherwise, they would die from freezing.

The chemistry behind the floating of ice is like this: Water has hydrogen bonds in between them. Hydrogen bonds are non-bonded interactions between negatively charged and positively charged atoms. There is always an attractive force existing between oxygen atoms of one water molecule and the hydrogen atoms of another water molecule. In liquid form, water makes and breaks the H bonds, as the molecules have high energy. When the water reaches four degrees Centigrade, one molecule forms 4 H bonds with four other water molecules. As the water cools and becomes ice, the molecular attractive forces become rigid, and the molecules do not move. The molecules form a crystalline lattice, and harbor some spaces in between the lattice. Hence, ice becomes less dense, and floats to the surface when submerged.


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