Diffusion in gases
2 marks · EasyA small bottle of perfume breaks at one end of a corridor 18 metres long. If perfume particles travel randomly at an average speed of 600 m/s, calculate:
The time it would take a perfume particle to reach the other end in a straight line, in seconds.
Explain why the actual time to smell the perfume at the other end is much longer.
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(a) 0.03 seconds
(b) Particles do not travel in straight lines, they collide with air particles and take random paths, so diffusion is much slower.
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Marking points
M1 (a) · 1 mark · Correctly calculates time using t = d / v.
B1 (b) · 1 mark · Explains the delay is due to random movement and frequent collisions.
Worked solution
a) Time = 18 m / 600 m/s = 0.03 s b) In reality, perfume particles take much longer to get to the other end because they frequently bump into (collide with) air particles and change direction.