Movement of molecules from an area of higher concentration to an area of lower concentration.

• A. Osmosis
• B. Diffusion
• C. Active Transport
• D. Passive Transport

Answer: (B)

Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration, driven by their random motion. This process continues until the concentrations equalize and no energy input is needed, so it’s a form of passive transport. It differs from osmosis, which is specifically the diffusion of water across a semipermeable membrane, often in response to solute differences. Active transport involves energy to move substances against their gradient, whereas diffusion occurs down the gradient without energy. In everyday terms, substances spread out naturally from where they’re more concentrated to where they’re less concentrated, until balance is reached.