Question

why are we not able to smell an unlit incense stick from a distance wheras we are able to smell a lit one from a distance ?

Answer 1

The fragrance of the incense stick does not reach us when it is not lit, as the molecules of the incense stick are closely bound to the stick and the diffusion of the fragrance is very less. However on burning the incense stick the fragrant molecules come in the vapour phase and are diffused in the surrounding , thus we are able to smell the fragrance of the stick.