How does roses smell so good?

Gasses have typical properties of evaporation and diffusion. The fragrance molecules with greater K.E evaporate from the surface of rose flower in gaseous state. These molecules due to their constant motion strike with air molecules and transfer their fragrance to these molecules by diffusion.This process continue more and more, the air molecules get fragrance.so, the pleasant smell is felt, when a person passes by a rose garden.