Science 6 · Unit 2: Materials: properties and changes · Cambridge Primary Science Stage 6

Questions

1. 1. What is a physical change?

   • a change that can never be undone
   • a change that makes a new substance
   • a change in how a substance looks or feels, with no new substance made
   • a change in weight only
   Check

2. 2. Why is melting ice a reversible change?

   • It burns.
   • It can never be undone.
   • The water can be frozen back into ice.
   • It makes a new substance.
   Check

3. 3. Which change is irreversible?

   • melting butter
   • dissolving salt
   • burning wood
   • freezing water
   Check

4. 4. Is boiling an egg reversible or irreversible?

   • reversible
   • irreversible
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5. 5. Is dissolving salt in water reversible?

   • Yes, the water can be evaporated to get the salt back.
   • Only if you freeze it.
   • No, the salt is gone forever.
   • No, it makes a new substance.
   Check

6. 6. Which change is reversible?

   • baking a cake
   • burning a match
   • rusting a tin can
   • melting butter in a pan
   Check

7. 7. What does 'rate of dissolving' mean?

   • the colour of a solution
   • how hot the solvent is
   • how much a solution weighs
   • how fast a solute dissolves
   Check

8. 8. Name a way to make sugar dissolve faster in coffee.

   • leave it still
   • cool the coffee
   • stir it
   • use bigger sugar lumps
   Check

9. 9. Does sugar dissolve faster in hot or cold water?

   • hot water
   • cold water
   Check

10. 10. How does heating a solvent help a solute dissolve faster?

    • It makes the solute heavier.
    • The particles slow down.
    • The particles gain energy and move faster.
    • The particles get bigger.
    Check

11. 11. Zara's results: 20 °C 90 s, 40 °C 40 s, 60 °C 25 s, 80 °C 15 s. What is the pattern?

    • The hotter the water, the faster the sugar dissolves.
    • Temperature makes no difference.
    • The hotter the water, the slower it dissolves.
    • It only dissolves at 80 °C.
    Check

12. 12. In Zara's test, what was the dependent variable?

    • the water temperature
    • the size of the jar
    • the time for the sugar to dissolve
    • the amount of sugar
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13. 13. Give two control variables for Zara's test.

    • only the colour of the jar
    • the temperature and the time
    • nothing needs to stay the same
    • the amount of sugar and the amount of water
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14. 14. Mrs Pather's warm tea still had sugar at the bottom. Why?

    • The sugar was too small.
    • The tea was not hot enough and she didn't stir it enough.
    • The cup was too big.
    • Sugar never dissolves in tea.
    Check

15. 15. Will sugar dissolve on its own in cold water if left long enough?

    • No, never.
    • Only if it is boiled.
    • Only if it is frozen.
    • Yes, because particles are always moving.
    Check

16. 16. When a match burns, what does the wood change into?

    • sugar
    • carbon, a black substance
    • more wood
    • water
    Check