(a) The molecules of gas have high kinetic energy due to which they keep moving in all directions and hence fill the vessel completely in which they are kept.
(b) A gas exerts pressure on the walls of the container because the molecules of the gas are in constant random motion due to high kinetic energy. These molecules constantly vibrate, move and hit the walls of the container thereby exerting pressure on it.
(c) The molecules/particles of the wooden tables are tightly packed with each
other, there is no intermolecular space, it cannot be compressed, it cannot flow, all these characteristics are solid. So wooden table should be called a solid. ‘
(d) We can easily move our hands in the air but to do the same through a solid block of wood we need a karate expert. It is because the molecules of the air have less force of attraction between them and a very small external force can separate them and pass through them. But in the case of solids, the molecules have the maximum force of attraction, the particles are tightly bound due to this force. Hence a large amount of external force is required to pass through the solid.