What is the process by which a gas moves from an area of higher concentration to an area of lower concentration?

The process in which a gas moves from an area of higher concentration to an area of lower concentration is known as gaseous diffusion. This occurs due to the natural kinetic energy of gas molecules, which causes them to move randomly and spread out to fill available space. As a result, over time, the concentration of the gas becomes more uniform, transitioning from areas of higher concentration to those of lower concentration until equilibrium is reached.

This concept is fundamental in various contexts, such as in the exchange of gases in the lungs, where oxygen diffuses from alveoli (area of higher concentration) into the blood (area of lower concentration), allowing for essential respiratory functions. The other processes listed do not correctly describe the movement of gas based on concentration differences. Gaseous absorption, for instance, involves gas being taken up by a liquid or solid, gaseous expansion refers to the increase in volume of a gas when conditions change, and gaseous reduction does not define a recognized physical process in gas behavior.