Science 8 · Unit 5: Materials and cycles on Earth · Cambridge Lower Secondary Science Stage 8

Questions

1. 1. What is a pure element?

   • a mixture of metals
   • a compound
   • a substance made of only one type of atom
   • any shiny metal
   Check

2. 2. What are diamonds made of?

   • carbon atoms
   • silver atoms
   • nitrogen atoms
   • hydrogen atoms
   Check

3. 3. What gives a diamond a blue colour?

   • boron atoms mixed with the carbon
   • hydrogen atoms only
   • nitrogen atoms
   • iron atoms
   Check

4. 4. What colour is a diamond with nitrogen atoms mixed with the carbon?

   • blue
   • green
   • yellow
   • red
   Check

5. 5. Silver marked 925 contains what percentage silver?

   • 9.25%
   • 925%
   • 75%
   • 92.5%
   Check

6. 6. What does 24 carat gold mean?

   • 24% gold
   • 2.4% gold
   • half gold
   • pure gold - 24 parts out of 24
   Check

7. 7. What percentage of gold is in 18 carat gold?

   • 50%
   • 18%
   • 90%
   • 75%
   Check

8. 8. What percentage of gold is in 9 carat gold?

   • 37.5%
   • 90%
   • 9%
   • 50%
   Check

9. 9. What percentage of gold is in 22 carat gold?

   • 91.7%
   • 100%
   • 88%
   • 22%
   Check

10. 10. What percentage of gold is in 14 carat gold?

    • 70%
    • 58.3%
    • 41.7%
    • 14%
    Check

11. 11. In 18 carat gold, what are the other six parts usually?

    • iron only
    • carbon
    • plastic
    • copper or silver
    Check

12. 12. Why are gold rings often less than 24 carat?

    • Alloys are softer.
    • Pure gold is not shiny.
    • Gold alloys are harder than pure gold.
    • Pure gold is too hard.
    Check

13. 13. Look at the table. 24 carat (pure) gold has a hardness of 30 and 18 carat gold has 120. What does this show?

    • Carats don't affect hardness.
    • The 18 carat alloy is much harder than pure gold.
    • They are the same.
    • Pure gold is hardest.
    Check

14. 14. Look at the table. You might expect 9 carat gold to be the hardest, but it is not. What could explain this?

    • The data must be fake.
    • 9 carat gold is pure.
    • The other metals mixed in, not just the amount of gold, affect hardness.
    • Hardness can't be measured.
    Check

15. 15. Is advice based on data from a hardness test science or opinion?

    • opinion, because a person said it
    • opinion, because gold is pretty
    • science, because it is based on evidence
    • neither
    Check

16. 16. What percentage of silver is in silver marked 900?

    • 92.5%
    • 900%
    • 90%
    • 9%
    Check

17. 17. What colour is a pure diamond?

    • blue
    • colourless
    • yellow
    • green
    Check

18. 18. 1000 g of seawater contains 35 g of salts, and 68% of the salt is sodium chloride. What mass of sodium chloride is there?

    • 11.2 g
    • 35 g
    • 68 g
    • 23.8 g
    Check