Diffusion describes which of the following?

• A. Movement of particles from an area of high concentration to an area of low concentration.
• B. Movement of particles from an area of low concentration to an area of high concentration.
• C. The dissolution of a solute.
• D. The change of state from gas to liquid.

Answer: (A)

Diffusion is the spread of particles from an area of higher concentration to an area of lower concentration due to their constant random motion. This passive process continues until the distribution becomes uniform, and it requires no energy input. It explains everyday observations like the scent of perfume gradually filling a room or oxygen moving from air in the lungs into the blood. It’s not about moving from low to high concentration (that would need energy), nor about dissolving a solute in solvent, nor about changing state like gas turning into a liquid.