the process when molecules tend to move from an area of high concentration to an area of low concentration.

The process when molecules move from an area of high concentration to an area of low concentration is called diffusion. It is a passive transport mechanism that does not require energy input. Molecules move down their concentration gradient due to their constant random motion until equilibrium is reached, where the molecules are uniformly distributed but still moving randomly. Diffusion occurs naturally in gases, liquids, and solids, and is essential for many biological processes such as the movement of oxygen and nutrients across cell membranes.