Q.Describe the structure of the common form of ice.

In the water molecule the oxygen atom is $sp^3$ hybridised, giving a bent (angular) shape with a bond angle of about $104.5^\circ$ and an O–H bond length of $95.7\,pm$; two of the four hybrid orbitals form O–H sigma bonds while the other two hold lone pairs of electrons. This bent geometry combined with the large electronegativity difference between O and H makes water strongly polar, with a dipole moment of about $1.85\,D$. Because each molecule has two O–H hydrogens (donors) and two lone pairs (acceptors), a single water molecule can, in principle, participate in up to four hydrogen bonds with its neighbours, building an extensive three-dimensional hydrogen-bonded network. In ice, this ordering becomes a fixed open, cage-like tetrahedral lattice in which every oxygen is hydrogen-bonded to four others, leaving empty space that makes ice less dense than liquid water. This extensive hydrogen bonding is responsible for water's many anomalously high physical properties — its high melting and boiling points, high specific heat capacity, high heat of vaporisation, and high surface t …