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# 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.￼

-Nandita Bhattacharya, Subject matter expert at Edumarz

Answer: (a) A gas fills completely the vessel in which it is kept.

The forces of attraction between the particles of gases are negligible but kinetic energy is very high. So, particles of gases moves continuously in different directions. With different speed so they do not have fixed volumes and fills the container completely in which they are kept.

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

Gas molecules have negligible forces of attraction between them so they have highest kinetic energy. Due to this the gas particles moves in every direction in the container and hits the walls of the container from all sides. Thereby we say that gases exerts pressure on the walls of container.

(c) A wooden table should be called a solid.

A wooden table is has a definite shape, volume and size. It is rigid and cannot be compressed by applying pressure. It possesses all of the general characteristics of solid therefore it is 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.

Air is gas and wood is solid due to the density difference between the particles of a gas and solid. Particles of gas are very far away from each other whereas the particles of solid are very closely packed with each other. For this reason we can easily move our hand in air but to do the same with a wooden block we need a karate expert.