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.
NCERT Class 9th Science Ch 1 Matter in Our Surroundings
Answers
a)
Gas fills completely The vessel in which it is kept because the due to high kinetic energy and negligible forces of attraction the particles of a gas are moving with a speed in all directions and the gas completely filled The vessel in which it is kept..
b)
A gas exerts pressure on the walls of the container because of High kinetic energy & negligible forces of attraction the particles of a gas move with high speed in all direction when the fast moving gas particles hit the walls of the container from inside they exert a gas pressure.
Hence, the pressure exerted by gas is due to the constant collisions of the fast moving gas particles against that inner walls of the container.
c)
A wooden table should be called a solid because a wooden table is a rigid object having a definite shape and definite volume.
Since a wooden table has rigidity, definite shape & definite volume it should be called a solid.
d)
Because it is a gas and the particles of gas are very far apart and they have a very weak forces of attraction between them . The extremely weak forces between the particles of air can be overcome easily due to which we can easily move our hand in air.
The particles of solid block of wood very closely packed and solid particles have a strong forces of attraction between them. So it needs are strong force to overcome the strong interparticle attraction of block of wood and break it apart by moving our hand which only a Karate expert can apply.
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Matter
Explanation:
a). Gas fills the vessel completely in which it is kept due to the nominal force of attraction between the gas particles. Due to the high presence of kinetic energy in gas particles, they are always in motion and spreads out in all directions.
b). Gas particles collide with the walls of the container due to the high presence of kinetic energy. The Less intermolecular force of attraction and high kinetic energy makes them exert pressure.
c). A wooden table should be called a solid because it is fixed in shape, volume, and it is incompressible. It is high in density because of the high force of attraction between the particles.
d). We are able to move our hand freely through the air because the force of attraction in the gases is very less and therefore, one can easily move out the hand while it requires expertise to move the hand out of a solid block due to the strong intermolecular force of attraction which requires strong force to break it.
Learn more: matter
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