Science 8 · Unit 8: Chemical reactions · Cambridge Lower Secondary Science Stage 8

Questions

1. 1. What is the chemical name for rust?

   • iron chloride
   • hydrated iron oxide
   • copper oxide
   • iron carbonate
   Check

2. 2. What two things does iron need to rust?

   • oxygen (air) and water
   • only water
   • heat and light
   • salt and sugar
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3. 3. Look at Zara's three tubes. In which tube will the nail go rusty?

   • tube B, with water and air
   • none of them
   • tube A, with dry air
   • tube C, with water and no air
   Check

4. 4. Look at tube C. How does it keep air away from the nail?

   • The nail is painted.
   • Calcium chloride removes air.
   • The water is boiled to remove air and covered with oil.
   • The tube is very cold.
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5. 5. Look at tube A. What does the calcium chloride do?

   • absorbs oxygen
   • heats the tube
   • makes the nail rust faster
   • absorbs water to keep the air dry
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6. 6. The nail in tube A rusts a little. How might this happen?

   • Oil leaked in.
   • Iron rusts in totally dry air.
   • The nail was gold.
   • The calcium chloride didn't absorb all the water vapour.
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7. 7. Name a way to stop iron rusting.

   • paint it
   • leave it outside in rain
   • soak it in salt water
   • scratch it
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8. 8. What is galvanising?

   • coating iron with zinc to prevent rusting
   • heating iron until it glows
   • adding water to iron
   • painting iron red
   Check

9. 9. What is the general word equation for a metal reacting with oxygen?

   • metal + water → metal oxide
   • metal + oxygen → metal oxide
   • metal + oxygen → metal hydroxide
   • metal + acid → oxygen
   Check

10. 10. What is formed when magnesium burns in air?

    • magnesium carbonate
    • magnesium chloride
    • magnesium oxide
    • magnesium hydroxide
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11. 11. Is rusting a useful reaction?

    • It has no effect.
    • Yes, it makes iron magnetic.
    • No, it damages iron and steel.
    • Yes, it strengthens iron.
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12. 12. To test if warmth speeds up rusting, what is the independent variable?

    • the volume of water
    • the temperature
    • the amount of rust
    • the type of nail
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13. 13. In that test, how could you measure the amount of rusting?

    • compare the mass gained or rust seen after the same time
    • count the nails
    • measure the water colour only
    • smell the nail
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14. 14. Why does salty water make iron rust faster?

    • Salt is a type of paint.
    • Salt removes oxygen.
    • Salt speeds up the rusting reaction.
    • Salt stops water reaching iron.
    Check

15. 15. A freshly cut piece of sodium is shiny but soon goes dull. Why?

    • It dries out.
    • It reacts with oxygen in the air to form an oxide.
    • It melts.
    • It absorbs light.
    Check

16. 16. Gold does not react with oxygen. What word describes it?

    • reactive
    • corrosive
    • magnetic
    • inert
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17. 17. A silver object that is not cleaned goes black over time. Why?

    • Silver rusts like iron.
    • Light turns it black.
    • Silver slowly reacts with substances in the air to form a black coating.
    • Dirt soaks into the silver.
    Check