Which statement correctly ranks diffusion rates from fastest to slowest?

Which statement correctly ranks diffusion rates from fastest to slowest?

• A. Liquids fastest, then gases, then solids
• B. Gases fastest, then solids, then liquids
• C. Solids fastest, then liquids, then gases
• D. Gases fastest, then liquids, then solids

Answer: (D)

Diffusion rate depends on how freely particles can move. In a gas, particles are far apart and zip around with little restriction, so substances spread through the medium very quickly—think of a scent quickly filling a room. In a liquid, particles are closer together and constantly collide, sliding past one another, so diffusion still happens but more slowly than in a gas. In a solid, particles are tightly packed in a fixed arrangement and can only move by small vibrations or by moving into vacancies, making diffusion the slowest. So the fastest to slowest order is gases, then liquids, then solids.

Diffusion rate depends on how freely particles can move. In a gas, particles are far apart and zip around with little restriction, so substances spread through the medium very quickly—think of a scent quickly filling a room. In a liquid, particles are closer together and constantly collide, sliding past one another, so diffusion still happens but more slowly than in a gas. In a solid, particles are tightly packed in a fixed arrangement and can only move by small vibrations or by moving into vacancies, making diffusion the slowest.

So the fastest to slowest order is gases, then liquids, then solids.