Final answer:
Perfume molecules are able to travel throughout a house due to diffusion, which is the movement of particles from an area of higher concentration to an area of lower concentration.
Step-by-step explanation:
Perfume molecules are able to travel throughout John's house because of diffusion.
Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
When the perfume is sprayed in his room, the scent molecules naturally diffuse from the spot where they left the bottle to all corners of the bathroom, and this diffusion continues until no more concentration gradient remains.
The molecules spread out and move down their concentration gradient, allowing the perfume scent to be smelled throughout the house.