Diffusion in gases

2 marks · Easy

At room temperature, particles in a gas travel at about 500 m/s. The laboratory is 6 m long.

Calculate:

(a)

How long it would take a particle, travelling in a straight line at this speed, to reach the other end of the laboratory.

[1 mark]

(b)

Explain why, in reality, it takes much longer for a smell to spread across the laboratory.

[1 mark]

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(a) 0.012 s

(b) Because gas particles keep bouncing off other particles and do not travel in straight lines.

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Marking points

M1 (a) · 1 mark · Correctly uses speed = distance/time or equivalent method.

B1 (b) · 1 mark · Explains that in reality particles do not go straight but keep colliding.

Worked solution

a) Time = distance / speed = 6 m / 500 m/s = 0.012 s

b) In reality, particles move randomly and keep colliding with other particles, so it takes much longer for them to diffuse across the lab.