A bottle of perfume is left in a room. The top is taken off the bottle. The smell of the perfume eventually fills the room. What is the name of this process?

The process you're describing is called diffusion. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. In this case, when the top of the perfume bottle is removed, the fragrance molecules start to spread out into the surrounding air in the room. Over time, these molecules move away from the concentrated area near the bottle and intermingle with the air particles in the room, leading to the scent being detectable throughout the entire space. This process continues until there is an even distribution of the perfume molecules throughout the room. Additionally, diffusion occurs due to the random motion of particles, driven by thermal energy, and is a fundamental concept in chemistry and physics.