Explain, in terms of the bonds present in NaCL & CH4, why their physical states are different?

NaCl (Sodium chloride)

NaCl
is a ionic compound in which the ions form ionic bond, ionic bond is a chemical bond in
which one atom loses one electron to form positive ion and that electron is accepted by
other atom to form negative ion.

This depends upon the
electronegativity, if the electronegative difference between the two atoms are more then
they form ionic bond. [Electronegativity = ability of the atom to pull electron more
towards itself]. In NaCl, Cl has more electronegativity than Na thus forming negative
ion and since Na loses one electron it form positive ion. Ionic compounds brittle and
hard in nature with high melting and boilling points and are highly soluble in
water.

CH4 (Methane)

CH4 is
covalent compound, a covalent compound is formed by covalent bond which is formed by
Sharing of pair of electrons between the atoms in a molecule. In covalent bond one
attains partial negative charge and another atom attains partial positive charge.
Covalent compounds are non electrolyte and poor conductors of heat and electricity,
covalent crystals are hard in nature