Lesson T6.1.3

T6.1.3 Diffusion and Brownian motion Quiz: KS3 Physics, Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T6.1.3, Diffusion and Brownian motion: 20 multiple choice questions for the KS3 Physics (National Curriculum), Unit 6: Matter and particles, written with Revision Ninja.

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The 20 questions

  1. What is diffusion?

    • The spreading out of particles from a region of high concentration to low concentration
    • The heating of a liquid in a sealed container until it boils and turns into vapour
    • The movement of particles from a region of low concentration to a region of high concentration
    • The sudden splitting of a single particle into two smaller and separate particles

  2. Which substances diffuse fastest?

    • Solids
    • Liquids in a tall jar
    • Rocks in a stream
    • Gases

  3. What drives diffusion?

    • A difference in colour between two regions
    • A difference in concentration between two regions
    • A difference in mass between two regions
    • A difference in the size of the container

  4. A drop of food colouring is added to still water. What happens over time?

    • The colour turns into a solid film that floats on the top
    • The colour evaporates from the water surface almost immediately
    • The colour stays in one drop at the bottom of the glass
    • The colour spreads evenly through the water

  5. Why is diffusion slower in liquids than in gases?

    • Liquid particles are heavier, so they move more slowly than gases
    • Liquid particles have no motion, so they cannot spread at all
    • Liquid particles are closer together and collide more often
    • Liquid particles repel each other strongly and stay apart from one another

  6. What is Brownian motion?

    • The rotation of a magnet in a field that is steadily getting stronger
    • Random movement of tiny visible particles caused by collisions with faster particles
    • The vibration of a solid that has been heated up to a high temperature
    • The steady flow of water through a pipe that is connected to a pump

  7. What causes the random jiggling of smoke particles seen under a microscope?

    • Gravity pulling the smoke particles up and down
    • Collisions with the fast-moving gas particles around them
    • The smoke particles being charged
    • The smoke particles being magnetised

  8. Why does a smell from a cooking pan reach the other side of a room?

    • The smell is produced by electric charges
    • The smell is carried by magnetic fields
    • The smell is heavier and sinks to the floor
    • Gas particles diffuse through the air

  9. Which statement about diffusion in gases is correct?

    • It happens only in a vacuum
    • It is slower when the gas is warmer
    • It is unaffected by temperature
    • It is faster when the gas is warmer

  10. What does Brownian motion show about particles?

    • Particles are all exactly the same size and shape as each other
    • Particles stop moving entirely when a liquid is heated to its boil
    • Particles in gases and liquids are constantly moving at random
    • Particles in solids move freely around the whole of the room

  11. Which situation shows diffusion in a liquid?

    • A sugar cube slowly dissolving and spreading through a cup of tea
    • A candle wax melting in the heat and then solidifying again
    • A balloon being inflated slowly with air from a small pump
    • A magnet attracting an iron nail that is resting on a table

  12. Why does a perfume spread through a room over several minutes?

    • Its particles are pushed by the air conditioning unit in the room
    • Its particles are charged and repel each other across the room
    • Its particles diffuse through the air from high to low concentration
    • Its particles are attracted to the walls and stick to the surface

  13. A gas jar of bromine is placed under a jar of air. What happens?

    • The bromine turns into a solid that sinks down to the bottom
    • The air turns into bromine and changes the colour of the jar
    • The bromine gas spreads upwards and mixes with the air
    • The bromine falls and stays at the bottom of the jar as a layer

  14. What effect does a higher concentration difference have on diffusion?

    • Diffusion happens more slowly
    • Diffusion reverses direction
    • Diffusion stops completely
    • Diffusion happens faster

  15. Why do the particles of an ink drop spread out over time in water?

    • They are pushed by a magnetic field
    • They are heated and expand into the water
    • They are attracted to the bottom of the container
    • They move randomly and collide with water particles

  16. Which of these is an example of Brownian motion?

    • A ball rolling steadily down a long smooth slope made of wood and then stopping
    • A magnet pulling a paper clip across a flat wooden table top and holding it
    • A kettle boiling water in a metal pan on a hot electric stove for several minutes
    • Pollen grains jiggling on the surface of water when viewed under a microscope

  17. What happens to diffusion in a solid?

    • It happens just as easily as in gases in the same container
    • It stops completely at room temperature because it is solid
    • It is faster than in gases because the particles are very close
    • It is very slow because particles are held in fixed positions

  18. Which statement about the particles that cause diffusion is correct?

    • They move only in straight lines in one direction
    • They stop moving once they reach equilibrium
    • They are constantly moving at random
    • They move only when a magnet is nearby

  19. A thin strip of purple dye spreads through hot water faster than through cold water. Why?

    • Hotter water particles move faster, so the dye spreads more quickly
    • Cold water has no particles in it, so the dye cannot spread
    • Hot water stops the dye from moving, so it spreads very slowly
    • Hot water is denser, which pushes the dye into the water

  20. Which of these shows that particles move even when nothing seems to be happening?

    • A rock sitting still on the top of a hill in the sun
    • Smoke jiggling in still air under a microscope
    • A closed door that stays shut against the wall of a room
    • A stationary book lying flat on a desk in a room

All KS3 Physics quizzes