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Q3. 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.

Answer :

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



(b) A gas exerts pressure on the walls of the container because they possess 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.



(c) A wooden table should be called a solid because it has all the properties of a solid such as: definite size and shape, intermolecular attraction between closely packed particles, it is rigid and cannot be compressed



(d) We can easily move our hand in the air because the force of attraction between the particles of air is weak, hence breaking it is easy but 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 high, so breaking it is difficult.