T3.1.3 Diffusion and the particle model Quiz: KS3 Chemistry, Unit 3

The 20 questions

1. What is diffusion?

   • The joining of particles into a solid crystal as the liquid cools slowly down
   • The movement of particles from low to high concentration, against the gradient
   • The breaking of particles into smaller parts during a chemical reaction in a flask
   • The spreading of particles from high concentration to low concentration

2. Why does diffusion happen in gases?

   • Particles are moving randomly and spread out to fill the space
   • Particles are fixed in place and pushed slowly around by the force of gravity
   • Particles stop moving and settle to the bottom of the container under gravity
   • Particles are attracted to the walls of the container, so they stay close to them

3. Which is faster, diffusion in a gas or diffusion in a liquid?

   • They are the same speed
   • Diffusion in a liquid
   • Diffusion in a gas
   • Neither happens in a liquid

4. Why does diffusion happen very slowly in solids?

   • Solid particles are fixed in position and vibrate, so they cannot move far
   • Solid particles repel each other strongly, so they stay as far apart as possible
   • Solid particles are always heavier than gas particles of the same substance
   • Solid particles have no motion at all, so they cannot be moved or pushed

5. A few drops of food colouring are added to still water and spread out. Which explanation fits the particle model?

   • The water particles pull the colour towards the surface of the still water
   • The colour particles become heavier and sink straight to the bottom of the dish
   • The coloured particles move randomly and spread out among the water particles
   • The colour particles are destroyed by the water in a chemical change over time

6. Why does a perfume smell reach the other side of a room?

   • Perfume particles stop moving when they reach the air and wait there to be smelt
   • Perfume particles diffuse through the air as they move randomly
   • Perfume particles are pushed across the room only by the movement of the wind
   • Perfume particles are heavier than air and so they fall slowly through the room

7. Which factor makes diffusion happen faster?

   • A solid medium with fixed particles
   • A higher temperature, so particles move faster
   • A lower temperature, so particles slow down
   • A larger container with no change in temperature

8. A drop of ink spreads through a glass of water over time. Why does the ink spread evenly through the water?

   • The ink particles move from a high concentration to a low concentration
   • The ink particles are destroyed by the water and the colour fades quickly
   • The ink particles move upward only, against gravity, as the water warms
   • The ink particles collect in the middle of the glass and stay there for hours

9. Which statement best describes diffusion in liquids?

   • Particles only spread upward in the liquid, because heat always pushes them up
   • Particles stop moving once they touch each other and stay fixed in place there
   • Particles slowly move randomly and spread out until evenly mixed
   • Particles move in one fixed direction only, along a single straight path

10. Why does diffusion of a gas slow down if the gas is cooled?

    • The particles gain energy and move faster, so the gas spreads more quickly
    • The particles become bigger and heavier, so they sink and spread more slowly
    • The particles lose energy, move more slowly and spread out more slowly
    • The particles change into a solid and stop moving, so they cannot spread at all

11. A gas spreads out in a container without being stirred. What does this suggest?

    • Gas particles are being pushed by a fan
    • Gas particles are attracted to the glass walls
    • Gas particles are all fixed in one corner
    • Gas particles are in constant random motion

12. Which idea from the particle model explains diffusion?

    • Particles are bonded into chains that cannot separate
    • Particles are in constant random motion
    • Particles are all the same size and never move
    • Particles are fixed in a regular lattice

13. Why does a smell from cooking spread through a room without any stirring?

    • Air particles stop moving and wait for smell particles to come to them slowly
    • The walls push air particles around the room in slow, steady circles all day
    • Air particles are moving constantly, carrying particles of smell with them
    • Air particles are all attracted to the floor and so they settle at ground level

14. Which statement correctly contrasts diffusion in gases and in liquids?

    • Gas particles diffuse faster because they are further apart and move more freely
    • Liquid particles diffuse faster because they are further apart and move more freely
    • Gas and liquid particles diffuse at exactly the same speed because they both move randomly
    • Gas particles do not diffuse at all because they are held in place by the container

15. A sugar cube dissolves in water and spreads through it over time without stirring. What process spreads the sugar particles?

    • Evaporation
    • Filtration
    • Chromatography
    • Diffusion

16. Why does a high concentration gradient make diffusion happen faster?

    • The particles stop moving when the concentration is high in the crowded area
    • More particles move out of the crowded area each second, so more cross
    • There are fewer particles, so they can move faster and cross the boundary sooner
    • The particles repel strongly from the low concentration area and so spread out

17. Which factor would make diffusion slowest?

    • A gas at room temperature in a small box, where the particles are crowded together
    • A hot gas in a large open container where the particles can spread freely
    • A cold, solid material with particles held in fixed positions
    • A warm liquid stirred gently in a beaker, which keeps the particles mixing well

18. A student says particles diffuse because they are attracted to one another. What is the correct idea?

    • Particles diffuse because they move randomly, not because they attract each other
    • Particles diffuse because they are fixed in place and vibrate into new spaces
    • Particles diffuse because heat constantly pushes them upward in the container
    • Particles diffuse because they repel the walls of the container at all times

19. Why does a cooking smell reach a distant room within minutes, but a drop of oil on water takes much longer to spread?

    • Oil particles are much smaller than air particles, so the oil spreads faster
    • Gas particles move much faster and more freely than liquid particles
    • The oil is much heavier than the cooking smell, so it stays on top of the water
    • Air is much denser than water, so the air in the room blocks any smell from travelling

20. In a model of diffusion, what does a concentration gradient describe?

    • A difference in the temperature between two regions of the same liquid sample
    • A difference in the number of particles per unit volume between two regions
    • A difference in the colour of two liquids that are kept in separate beakers
    • A difference in the mass of two solid blocks placed side by side on a bench

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