(a) When gas is stored in a container, the fast-moving particles of the gas collide with each other.
Also they collide with the walls of the container.
Thus gas exerts pressure on the walls of the container.
(b) As gasses have large inter-molecular space and weak intermolecular force of attraction. Therefore gasses do not have a fixed shape and volume.
They move freely in the vessel.
Hence, the gas particles spread out and fill a vessel completely
(c) Gasses are easily compressible as they have large intermolecular spaces.
The gas particles can come closer to each other when external pressure is applied to gasses.
Which is almost impossible in liquid as the intermolecular spaces in liquids are small.
The particles in a solid are very close to each other.Hence, they cannot be compressed by external pressure.
Final Answer: Hence (a) When gas is stored in a container, the fast-moving particles of the gas collide with each other.Thus gas exerts pressure on the walls of the container.
(b) As gasses do not have a fixed shape and volume.Hence, the gas particles spread out and fill a vessel completely
(c) Gasses are easily compressible as they have large intermolecular spaces.
The gas particles come closer on application of pressure.
Which is almost impossible in liquid and solid due to small intermolecular spaces.