Why Does Ice FLOAT in Water?


We all have seen ice cubes floating in a glass
of water and the sheet of ice formed over a lake that allows for skating. Water is actually one of the only known substances
on Earth that is able to float when frozen, but what’s so special about ice that allows
it to float in water? Water is a polar substance, meaning that the
molecules that make up water have a small disbalance of charge. In H2O molecules, Oxygen is “electron loving”,
or “electronegative”, and the Hydrogens are willing to lend it some electrons. Since Oxygen is a highly electronegative atom
and Hydrogen readily lends it some electrons, we call this “Hydrogen Bonding”. However, after the hydrogen lends electrons,
which have a negative charge, to oxygen, the Hydrogen atoms lose some negative charge and
the Oxygen atoms gain some negative charge. This makes the area around the hydrogen atom
areas slightly positive and the area around the Oxygen atom areas slightly negative. Since opposite charges attract and negative
charges repel, surrounding H2O molecules form a structure called a “lattice” with the
Oxygens away from other Oxygens, the Hydrogens away from other Hydrogens, and Oxygens close
to other Hydrogens. This is the secret to why ice floats on water. When the surrounding temperature is warmer
than 33 degrees F, the freezing point of pure water, the H2O molecules move around and are
no longer able to maintain their lattice structure. The lack of this lattice structure makes the
H2O molecules disordered and end up closer together. Because the molecules are closer together,
the water warmer than 33 degrees F is more heavy per unit of volume than ice that is
in its lattice structure. Since less dense objects float in more dense
objects, the slightly less dense ice floats to the top of water. This characteristic of water is essential
for aquatic life to occur. If ice sank in water, ice would form underneath
a body of water and eventually freeze the entire body of water. Because ice floats and forms at the top of
a body of water, it forms a “shield” of insulating protection that keeps the water
underneath warmer and the fish safe. The attraction between the slightly negative
Oxygen bonds and the slightly positive hydrogen bonds in the lattice structure of ice is so
strong that it could even rip apart steel if liquid water goes into a crack in the steel
and expands to form ice. Most substances become more dense when they
become cooler since, there are no polar molecules to form a lattice. Water’s unique ability of becoming less
dense when cold even keeps the Earth cooler by reflecting back sun shining on icebergs
floating in the Antarctic. Needless to say, there’s some awesome forces
behind the ice floating in your iced-tea.

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