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A smell crosses a room in seconds, yet a drop of dye takes minutes to spread through still water. Why?
AGas particles are heavier and so push harder
BGas particles are smaller and so slip past more
CGas particles are colder and so hold together
DGas particles are further apart and collide less
Answer & Solution
Correct answer: D. Gas particles are further apart and collide less
1. Diffusion happens because particles move randomly and keep bumping into others.
2. Each bump sends a particle off in a new direction, which slows its progress.
3. In a liquid the particles are close together, so bumps happen very often.
4. In a gas the particles are far apart, so a particle travels further between bumps.
5. That is why diffusion is much faster in a gas than in a liquid.
6. Being lighter does help a little, but pushing harder is not how diffusion works.
7. Cooling would slow particles down, which is the opposite of what is seen here.
_Source: Siyavula Natural Sciences Grade 8 (CC BY 4.0), Factors that affect the rate at which particles diffuse_