Final answer:
Diffusion is the process whereby molecules move spontaneously from an area of higher concentration to an area of lower concentration due to the random motion of molecules. It is a key concept in Biology and essential for the understanding of how substances move across cell membranes.
Step-by-step explanation:
The spontaneous movement of a substance from a region where it is more concentrated to a region where it is less concentrated is called diffusion. This process is a fundamental concept in Biology, particularly in cell biology and biochemistry. Diffusion occurs when molecules move on their own due to the kinetic energy they possess, which causes them to bounce around and spread out evenly in a given space.
During diffusion, substances move from an area of higher concentration to one of lower concentration, down their concentration gradient. An everyday example of diffusion is when a drop of food coloring spreads out in a glass of water until the color is distributed evenly throughout the liquid. This type of diffusion, known as free diffusion, occurs without any barriers to the movement of the molecules.
The principal force driving movement in diffusion is the random motion of molecules due to thermal energy, which leads to a net flow of matter from places of higher to lower concentration, seeking equilibrium.