What does the process of diffusion in gases refer to?

Diffusion in gases specifically refers to the process where gas molecules move from an area of higher concentration to an area of lower concentration. This movement occurs due to the random and continuous motion of gas particles, which allows them to spread out evenly in the available space.

When gas molecules collide and interact during their random motion, they tend to disperse, causing the concentration difference to diminish over time. This phenomenon is driven by the natural tendency of particles to achieve a state of equilibrium, where the concentration is uniform throughout the container.

The other options describe different concepts. The random movement of gas molecules is part of the diffusion process but does not capture the essence of diffusion itself, which emphasizes the concentration gradient. The evaporation of gas from a liquid state relates to phase changes rather than diffusion, and the reaction of gases under pressure pertains to chemical reactions and behavior of gases under different pressures, which is not indicative of the diffusion process.