Why do gases show high compressibility?

Explain:
$(a)$ Sponge,though compressible,is a solid.
$(b)$ Gases completely fill the vessel in which they are kept.

In which state of matter is the process of diffusion fastest?

Arrange the three states of matter in the increasing order of:
$(i)$ rate of diffusion
$(ii)$ particle motion

$(a)$ Enumerate the changes that take place in a liquid during evaporation.
$(b)$ How is the rate of evaporation affected by changes in the following? Justify your answer.
$(i)$ Temperature
$(ii)$ Wind speed
$(iii)$ Humidity

Define the following terms: $(i)$ Rigidity,$(ii)$ Compressibility,and $(iii)$ Density. Compare any two states of matter on the basis of the above-defined properties.