Science 8 · Unit 3: Forces and energy · Cambridge Lower Secondary Science Stage 8

Questions

1. 1. What is diffusion?

   • a solid melting
   • particles spreading from where they are more concentrated to where they are less concentrated
   • particles joining together
   • a liquid freezing
   Check

2. 2. Why does a drop of ink eventually colour all the water?

   • Ink particles move randomly and spread through the water.
   • The ink evaporates.
   • The ink sinks.
   • The water sucks it up.
   Check

3. 3. Why does ink spread faster in hot water?

   • The particles move faster at higher temperatures.
   • Hot water is thinner.
   • Ink likes heat.
   • There are more particles.
   Check

4. 4. Why does the colour of bromine gas become fainter further from the container?

   • The gas changes colour.
   • The particles spread out, so there are fewer in each space.
   • The gas disappears.
   • The particles get smaller.
   Check

5. 5. When a green gas has filled a bottle evenly, has particle movement stopped?

   • Yes, it stops completely.
   • Only the green particles stop.
   • Yes, the gas freezes.
   • No, the particles keep moving.
   Check

6. 6. In which states does diffusion happen?

   • only gases
   • only solids
   • liquids and gases
   • only liquids
   Check

7. 7. Is diffusion faster in gases or liquids?

   • gases
   • liquids
   Check

8. 8. A purple crystal dissolves. Why is the colour strongest at first?

   • The particles are concentrated in a small space.
   • The water is purple.
   • There are more particles at first.
   • The crystal is hotter.
   Check

9. 9. Apart from stirring, what would speed up the spreading of the purple colour?

   • using colder water
   • adding ice
   • using warmer water
   • using a bigger beaker
   Check

10. 10. Why does hot coffee smell stronger than cold coffee?

    • Hot coffee has more sugar.
    • More particles evaporate and diffuse faster from hot coffee.
    • Cold coffee has no smell particles.
    • Our noses work better in heat.
    Check

11. 11. How do animals use smell to find food?

    • They guess.
    • They move towards where the smell is stronger.
    • They listen instead.
    • They move towards where the smell is weaker.
    Check

12. 12. Two gas jars, one coloured and one colourless, are joined. What happens after some time?

    • They stay separate.
    • The coloured gas sinks to the bottom.
    • The particles mix evenly through both jars.
    • Both gases disappear.
    Check

13. 13. Does a gas need to be pushed to diffuse?

    • Yes, by gravity.
    • Only in the dark.
    • Yes, by a fan.
    • No, its particles move randomly on their own.
    Check

14. 14. Why does a perfume smell spread across a room?

    • The air stops moving.
    • Light carries it.
    • Perfume particles are solid.
    • Perfume particles diffuse through the air.
    Check

15. 15. Zara is across the room when her mother opens a perfume bottle. Which change makes Zara smell it sooner?

    • Zara moves further away.
    • The perfume is colder.
    • The lid is put back on.
    • The air in the room is warmer.
    Check

16. 16. Arun says, 'When the orange colour has stopped spreading, the particles in the liquid have stopped moving.' Is he right?

    • Yes
    • No
    Check

17. 17. Which of these does NOT result in diffusion?

    • adding salty water to pure water
    • adding sand to water
    • adding milk to coffee
    • letting gas escape from a cylinder into the air
    Check