What term is used to describe the movement of substances from an area of high concentration to an area of low concentration without energy use?

The term that describes the movement of substances from an area of high concentration to an area of low concentration without the use of energy is known as passive diffusion. This process relies solely on the concentration gradient; substances naturally flow from regions where they are abundant to where they are less so, seeking equilibrium.

Passive diffusion is a fundamental concept in biology, particularly in understanding how molecules, such as gases or small solutes, move across cell membranes. Unlike active transport, which requires energy (typically in the form of ATP) to move substances against their concentration gradient, passive diffusion is a spontaneous and energy-efficient process.

In biological contexts, essential elements like oxygen and carbon dioxide move via passive diffusion, highlighting its importance in physiological systems. This mechanism is crucial for processes such as gas exchange in the lungs and nutrient absorption in cells.