Question

When someone leaves an outside door open on a cold, still day, it is often said that the person is letting in cold air. If so, how

Answer 1

Diffusion

Step-by-step explanation:

This process can be referred to as diffusion. The cold air moves from a region of high concentration (outside) to a region of low concentration (inside). The movement of these cold air is what is referred to as "letting in cold air".

NOTE: Diffusion is the process in which substances move from a region of high concentration to a region of low concentration. Just like when an insecticide is sprayed inside a closed room and then the room is later opened so as to allow the the sprayed insecticide leave the room.