Give reasons: (a) A gas fills completely the vessel in which it is kept. (b) A gas exerts pressure on the walls of the container. (c) A wooden table should be called a solid (d) We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert

A) Gases have a negligible intermolecular force between the gas molecules and for this reason the gas particles randomly move in all directions and so the vessel is filled with gas.

B) Gas particles have negligible intermolecular force and high kinetic energy and move in all directions at high speed. Due to this random motion, particles collide with each other as well as with the wall of the container and in this way, the gas particles exert pressure on the wall of the container.

C) A wooden table should be called solid because it has definite shape and volume, it is very rigid and there is strong attractive force between the molecules. 

D) Molecules in the gas have a very low intermolecular attraction, but in a solid block of wood the molecules are tightly packed with strong intermolecular force, hence this happens.