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 the air but to do the same through a solid block of wood we need a karate expert.

(a) A gas fills completely the vessel completely in which it is kept because gaseous particles possess very high kinetic energy which allows them to move randomly across all directions when kept in a container.

(b) A gas exerts pressure on the walls of the container because they possess very high kinetic energy, due to which they are under constant motion inside the container in random directions which causes them to hit the walls of the container and thereby creating vibrations and exerting pressure on the walls of the container.

(c) A wooden table should be called a solid because it has all the properties of a solid such as it has definite size and shape, occupies space and thus have a definite volume, intermolecular attraction between particles is very high and thus it is rigid and cannot be compressed anymore.

(d) We can easily move our hand in the air because the force of attraction between the particles of air is very weak, hence breaking it is very easy but when we have to do the same through a solid block of wood we need a karate expert as the force of attraction between the particles of solid block is very high thus making it difficult to move the hand through it.