Free Diffusion questions for IGCSE Chemistry (0620), part of States of matter. Each question has the answer and the marking points an examiner would look for.
Cotton wool soaked in concentrated aqueous ammonia is placed at one end of a long glass tube and cotton wool soaked in concentrated hydrogen chloride solution is placed at the other end. A white ring of ammonium chloride forms. Where does the ring form, and why?
position of ring
reason
A
nearer the ammonia end
ammonia has a lower Mr and diffuses faster
B
nearer the hydrogen chloride end
hydrogen chloride has a lower Mr and diffuses faster
C
nearer the hydrogen chloride end
ammonia has a lower Mr and diffuses faster
D
exactly in the middle
both gases diffuse at the same rate
Show answer
Answer: C
Question 2Multiple choice · 1 markA* challenge
Which gas would diffuse most slowly at room temperature?
A neon, Ne
B ammonia, NH₃
C methane, CH₄
D sulfur dioxide, SO₂
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Answer: D
Question 3Multiple choice · 1 mark
Why does the smell of perfume spread across a room?
A Perfume particles move randomly and mix with air particles.
B Perfume particles are heavier than air.
C Air particles are attracted to perfume particles.
D The perfume reacts with air.
Show answer
Answer: A
Question 4Structured · 4 marks
Diffusion explains everyday observations.
(a)
Explain why the smell of cooking spreads through a house.
[2]
(b)
Explain why a tea bag colours hot water faster than cold water.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
particles move randomly, mix with air
particles of the food vapour move randomly B1 and mix with the air particles, spreading out B1
2
(b)
faster particles at higher temperature
particles have more kinetic energy and move faster at higher temperature B2
2
Question 5Structured · 4 marks
A purple crystal of potassium manganate(VII) is placed at the bottom of a beaker of water. After a few hours the purple colour has spread through all of the water.
(a)
Explain these observations using the kinetic particle theory.
[3]
(b)
Suggest why diffusion is faster in a gas than in a liquid.
[1]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
random movement, high to low concentration
the particles of the crystal dissolve and move randomly B1 they move from a region of high concentration to low concentration B1 until they are evenly spread B1
3
(b)
gas particles move faster / more space
gas particles move faster and have more space between them B1
1
Question 6Structured · 2 marks
State what is meant by the term diffusion.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
The net movement of particles from a region of higher concentration to a region of lower concentration as a result of their random movement
The net movement of particles from a region of higher concentration to a region of lower concentration as a result of their random movement B2
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Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in