Question

Density of ice is less than that of water because of:
A. absence of hydrogen bonding
B. crystal modification of ice
C. open porous structure of ice is due to hydrogen bonding
D. Different physical states of these

Answer 1

The water is present in three states: Solid, liquid, and gases. In all three forms, the arrangement of hydrogen bonds is different. In the solid form of water (ice), the water is present in a crystalline state so the molecules present in it cannot freely move.

Complete step by step answer:
Water is a universal solvent and its most important property is that it is formed of polar molecules. In water, the two hydrogen bonds and one oxygen bond are joined with each other by a polar covalent bond. The water molecule is non-linear structure and has a bent geometry and due to the electronegative difference between the oxygen atom and hydrogen atom, partial negative charge is generated on the oxygen and partial positive charge is generated in the hydrogen. Due to this, the water molecule attracts other water molecules to form a hydrogen bond between them. In the liquid form, the hydrogen bond is continuously formed and broken due to the movement of water molecules in the system due to the presence of heat. When the temperature has increased the breaking of the bond is increased with the increased movement of a water molecule. When the temperature is reduced and water is frozen and forms a crystallized structure made up of hydrogen bonds. A very high amount of energy is required to break the bond in the crystalline structure. In the solid-state of water, each oxygen atom is surrounded by four hydrogen atoms which are loosely held. The two hydrogens are covalently bonded to the oxygen atom and two other hydrogen atoms are bonded to the lone pairs of the oxygen atoms. Due to the open porous structure of ice, the density of ice is less than water.

So, the correct answer is Option C.

Note: For the given statement: Density of ice is less than that of water, option (B) can also be considered as in crystal structure, the hydrogen bonds are linearly bonded and very high energy is required to break the hydrogen bond.