Answer my question
a. As the particles in a gas have large intermolecular spaces between them, they move about freely at very high speeds. Hence the gas particles spread very rapidly in the space provided and tend to stay apart as much as possible. Thus a gas fills up the space available to it.
b. In solids the pressure is because of the mass.
In liquids the pressure is due to density and volume of liquids.
but gas neither have fix mass nor volume, here the pressure is due to the collision of molecules of gas with the wall of container.
Gas molecules are in random motion, during random motion the molecules collide with each other and also with wall of container. When the gas molecules collide with wall it exerts a force on the wall.
Pressure of a gas is the resultant force exerted on per unit area of wall due to collision of all the molecules on the wall.
In short,
Particles of gas move randomly in all directions at high speed. As a result, the particles hit each other and also hit the walls of the container with a force. Therefore, gas exerts pressure on the walls of the container.
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