Melting of Ice
Overview
This simulation starts with water molecules in the shape of an ice
crystal lattice below the freezing point. The lattice is oriented to
show the axis along which a hexagonal symmetry can be seen. Oxygen
atoms are colored red, and hydrogen atoms are colored white. As the
temperature is increased, the lattice disorders, and the hexagonal
symmetry disappears. Thus, the ice has melted.
Why the ice melts
The electron cloud in the water molecule is spready unevenly within
the molecule. Specifically, oxygen has more protons in its nucleus
than does hydrogen, and the result is that the electrons in the water
molecule are more concentrated around oxygen than around hydrogen.
(This effect is also hinted at by looking for large differences in
electronegativity values of the atoms involved.) The result is a
significant separation of charge, with oxygen being slightly negatively charged
and hydrogen slightly positively charged. The positive hydrogen end
of one molecule can interact favorably with the negative region of
another water molecule, setting up a electrostatic attraction between
molecules. This helps explain why the lattice forms in the first place.
However, molecules are in motion due to their kinetic energy, which
depends directly on temperature. When the temperature is low, most of
the water molecules have insufficient kinetic energy to break up the
lattice. As the temperature is increased, the water molecules
eventually gain enough
kinetic energy to disorder (or melt) the ice
lattice.
For more information about ice and water, see, for example:
Ice (Wikipedia)
Hexagonal Ice (Ice Ih)
Water and its structure