Why a material's molecules decide what it can do

Answer Key - Grade 10 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   A PTFE chain has 500 repeat units, each C₂F₄ with a mass of 100 g/mol. What is the chain's molar mass, Bo?

   50,000 g/mol
2. 2.

   A PVC chain has 600 repeat units, each C₂H₃Cl with a mass of 62.5 g/mol. What is the chain's molar mass, Esme?

   37,500 g/mol
3. 3.

   Hammered copper flattens, but a hammered salt crystal shatters. Which structural idea explains the difference, Jun?

   • Metal layers slide while shared electrons hold them; sliding salt ions meet like charges
   • Salt particles are lighter than copper atoms, so a hammer breaks them apart more easily
   • Copper has no bonds between its atoms, so its layers can flow like a liquid under a hammer
4. 4.

   Brass is harder to bend than pure copper. What best explains it, Kira?

   • Brass has more free electrons than copper, so its bonds are stronger
   • Zinc atoms are a different size, so the layers of atoms cannot slide as easily
   • Zinc atoms are lighter than copper atoms, so the metal packs more tightly together
5. 5.

   Graphite and diamond are both pure carbon, but only graphite conducts. Why, Luz?

   • Diamond atoms have no electrons of their own, so no electrons are available to carry current
   • Graphite has layers with free electrons; diamond's electrons are locked in bonds
   • Graphite has a little metal mixed in, while diamond has no metal inside it
6. 6.

   A rubber band stretches and snaps back. Which structure explains it, Noah?

   • Its atoms stretch apart when pulled and spring back when released like tiny springs
   • Long, coiled chains straighten when pulled and coil up again when released
   • Its free electrons slide along the band and pull the ends together
7. 7.

   A copper wire is coated with plastic. Why does the plastic stop the current, Pia?

   • The plastic repels electrons because it is charged negatively
   • Its electrons stay in bonds, so none are free to carry current
   • The plastic is thick enough that electrons cannot squeeze through

8. Read this first

   Wire coating scores (example scores, 1 to 5)

   material	flexibility	insulation	low cost
   PVC plastic	4	5	4
   natural rubber	5	5	2
   copper	3	1	3

9. 8.

   A coating needs an insulation score of at least 4 and a low-cost score of at least 3. Which material passes, Ren?

   • PVC plastic and natural rubber, which both insulate well
   • Natural rubber only, since it is the most flexible
   • PVC plastic only, since rubber's cost score is 2
10. 9.

    A coating needs an insulation score of at least 4 and a total of at least 12. Which materials pass, Tala?

    • PVC plastic alone, since rubber's total of 12 cannot beat PVC's 13
    • Neither material, since a total of 12 is not above the limit of 12
    • PVC plastic and natural rubber, with totals of 13 and 12
11. 10.

    Flexibility now counts triple, and the other two criteria count once. Which material has the highest total, Zee?

    • Copper, since its flexibility counts triple
    • PVC plastic, the winner with 13 against 12 before weighting
    • Natural rubber, with 22 against PVC's 21