Final answer:
Perfume molecules diffuse through the air until they are evenly distributed throughout the room, where they bind to receptors in the olfactory neurons, triggering the sense of smell.
Step-by-step explanation:
When perfume molecules reach the other side of a room, they continue to diffuse until they are uniformly distributed throughout the space. The perfume molecules individually move in random directions as they are in constant and random motion, which eventually causes the aroma to spread. This process called diffusion happens because molecules move from an area of high concentration to an area where they are less concentrated, driven by their kinetic energy. Additionally, according to Graham's Law of effusion, lighter gas molecules will effuse faster than heavier ones, which can be the case with the volatile chemicals in perfume. Once diffused, the perfume molecules bind to receptor proteins in olfactory neurons, stimulating the sense of smell.