Question

When we lit an incense stick its fragrance spreads to all rooms why

Answer 1

When we lit an incense stick it's fragrance spreads to all rooms because of the process of diffusion i.e. the movement of particles from a region of high concentration to a region of low concentration. That is why for example, we observed that the smell of hot food spreads to whole of the rooms, but to get the smell of the cold food we have to go close.

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