Misconception in Diffusion's Mechanism

Steps:

• Define diffusion as the net movement of particles from high to low concentration due to random motion.
• Assess A: Diffusion can involve any particles, not just water, like gases or solutes.
• Assess B: Diffusion occurs across partially permeable membranes but also in air or without membranes.
• Assess C: Diffusion applies to gases and liquids, not limited to solutions.
• Identify D as incorrect: It implies only directional movement, ignoring random motion.

Why D is correct:

• Diffusion involves random molecular movement in all directions; net flow is down the gradient, per Fick's first law (J = -D * dc/dx).

Why the others are wrong:

• A is correct: Diffusion moves any particles, including non-water molecules like oxygen.
• B is correct: While often across membranes, diffusion happens without them, e.g., perfume in air.
• C is correct: Diffusion occurs in gases and pure liquids, not just solutions.

Final answer: D