Question

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.

Answer 1

(a) The particles of gases have less force of attraction between them. The particles are free to move, so they will fill the vessel in which it is kept.

(b) The particles of gas have a weak force of attraction. So, they are constantly moving randomly. The pressure exerted by a gas is due to the random motion of particles in the gas. These particles collide with the walls of the container. These collisions apply force and hence pressure on the wall.

(c) The wooden table has a definite shape and a definite volume. The particles of wood are closely packed. They do not take the shape of any container. They are rigid in nature. Hence wooden table satisfies the properties of a solid.

(d) The particles of air are very loosely bounded. They are far away from each other having a lot of space between them. Hence we can easily move our hands in the air. But in a solid block, the particles are tightly held by a strong force of attraction. So there is some or no space between them. Hence we need a karate expert.