Q. Give reason.
a. The electric cables on poles hang loosely in summer but the same wires appear right. And not so loose in winter.
b. Ice occupies more space than water.
The constituent particles of the ice are not closely packed. In the ice water remains in the solid form in which each water molecule is tetrahedrally surrounded by the four other neighboring water molecules with their oxygen atom occupying the corner of the tetrahedron.
There are four hydrogen atoms two of the hydrogen atoms are bonded by the covalent bond while another two by the hydrogen bond. This gives a huge 3D structure having large vacant spaces. Due to this it has a large volume for the given mass of the water and hence less density.
P.S.Kindly post separate questions in separate threads.