Question

why does the spread of a burning insence stick spread in a room

Answer 1

HOLA friend!!
Rajdeep here.....

Do you know?
..
..

There is a phenomenon called "Diffusion"...

Now, what is Diffusion?
Diffusion is the phenomenon by which molecules of solid, liquid, or gas move from the region of their higher concentration to the region of their lower concentration.

The smell of a burning incense stick spreads in the room due to Diffusion.

The place where the stick is lit, is the region of higher concentration of the smell. Due to diffusion, the gaseous molecules move from that region (of its higher concentration) to the last corners of the room (region of lower concentration).

So, the smell spreads.
For a similar reason, one can smell a perfume sprayed by you in one corner of the room.

Thanks!!