$(a)$ Arrange the following in the increasing order of $(i)$ Force of attraction $(ii)$ Intermolecular space: Iron nail,Kerosene,and Oxygen gas. $(b)$ Define the following terms: $(i)$ Rigidity $(ii)$ Compressibility $(iii)$ Diffusion.

(N/A) $(i)$ Force of attraction: $\text{Oxygen gas} < \text{Kerosene} < \text{Iron nail}$.
$(ii)$ Intermolecular space: $\text{Iron nail} < \text{Kerosene} < \text{Oxygen gas}$.
$(b)$ $(i)$ Rigidity: It is the property of matter to maintain its shape against an external force.
$(ii)$ Compressibility: It is the property of matter by virtue of which its particles can be brought closer to each other under pressure.
$(iii)$ Diffusion: The spontaneous intermixing of particles of different types of matter due to their motion is known as diffusion.