Which process is illustrated by the spreading out of ammonia vapor in a closed room?

• A. Osmosis
• B. Diffusion
• C. Active transport
• D. Facilitated diffusion

Answer: (B)

Diffusion is the spreading out of particles from a region of higher concentration to a region of lower concentration due to their random motion. In a closed room, ammonia molecules move in all directions and gradually mix with the air, eventually reaching a uniform distribution without any energy input. This is different from osmosis (water moving through a membrane), active transport (energy-driven movement against a gradient across membranes), or facilitated diffusion (diffusion across a membrane aided by proteins). The scene with ammonia gas in air showcases diffusion in its simplest, membrane-free form.