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) A gas is able to fill the container because its particles are able to vibrate randomly in all the directions due to high kinetic energy as result they fill up the vessel completely in which they are kept.

(b) The particles of a gas have very high kinetic energy. They move randomly with high speeds in all directions. Due to this random movement, the particles hit each other and also the walls of the container. As a result, a gas exerts pressure on the walls of the container.

(c) A wooden table has a definite shape and a definite volume. The particles in a wooden table are tightly packed and have no intermolecular spaces and hence, it cannot be compressed. Since, a wooden table has the basic characteristics of a solid i.e. rigidity, definite shape and definite volume, it should be called a solid.

(d) We can easily move our hand in air but not do the same through a solid block of wood because of the differences in the intermolecular forces of attraction.Air has very low intermolecular force of attraction as result even small amount of force can separate air particles whereas in case of solids the intermolecular force of attraction are very strong and large amount of force is required to break them.This is the reason we can easily move our hand in air but t do the same through a solid block of wood we need a karate expert