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) There is little attraction between particles of gas. Thus, gas particles move freely in all
directions. Therefore, gas completely fills the vessel in which it is kept.
(b) The gas particles are in random motion due to weak intermolecular force of attraction.
These gaseous molecules continuously collide among themselves and they hit the walls of
the container with a greater force.
Therefore, gas exerts pressure on the walls of the container.
(c) A wooden table has a definite shape and volume. It is very rigid and cannot be
compressed i.e., it has the characteristics of a solid. Hence, a wooden table should be called a
solid.
(d) Particles of air have large spaces between them. On the other hand, wood has little space
between its particles. Also, it is rigid. For this reason, we can easily move our hands in air,
but to do the same through a solid block of wood, we need a karate expert.