You walk in the front door of your home. You smell an onion that someone is cutting in the kitchen. Explain why you are able to smell it, what this process is called, and what other types of substances exhibit this behavior.

This is the process of diffusion and is exhibited by gases. The compounds responsible for the smell of onions are released into the air and diffuse through out the house due to random molecular movement. This allows you to smell them at the entrance of your house.