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

'Osmosis is a special kind of diffusion'. Comment.

Why does water as steam cause severe burns,whereas water as ice has a cooling effect? Explain.

List any two properties that liquids have in common with gases.

Which phenomenon occurs during the following changes?
$(a)$ Formation of clouds.
$(b)$ Drying of wet clothes.
$(c)$ Wax melts in the sun.
$(d)$ Size of naphthalene balls decreases.

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.