Forces between molecules and boiling points

Answer Key - Grade 10 Science Worksheet

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

1. 1.

   Hydrogen sulfide boils at -60.33 °C. What is its boiling point in kelvins, to 0.01 K, Ari?

   212.82 K
2. 2.

   Methane boils at -161.5 °C (CRC). What is its boiling point in kelvins, to 0.01 K, Bo?

   111.65 K
3. 3.

   Ammonia boils at -33.35 °C. What is its boiling point in kelvins, to 0.01 K, Esme?

   239.8 K

4. Read this first

   Boiling points at 1 atm (PubChem (CRC, Merck))

   substance	boiling point (°C)	strongest attraction
   CH₄	-161.5	London dispersion
   H₂S	-60.33	dipole-dipole
   NH₃	-33.35	hydrogen bonding
   H₂O	100	hydrogen bonding
   F₂	-188.12	London dispersion
   I₂	184.4	London dispersion

5. 4.

   Using the table, why does H₂O boil so much higher than H₂S, Jun?

   • H₂S is ionic
   • Water forms hydrogen bonds
   • Water is the heavier molecule
6. 5.

   Using the table, which hydride boils lowest, Kira?

   • CH₄
   • H₂O
   • NH₃
7. 6.

   Using the table, why does I₂ boil at 184.4 °C but F₂ at −188.12 °C, Luz?

   • I₂ is larger, with stronger dispersion
   • I₂ forms hydrogen bonds with itself
   • F₂ is ionic
8. 7.

   What does a hydrogen bond connect, Pia?

   • Two H atoms inside one single molecule
   • An H to another molecule's N, O or F
   • Two ions
9. 8.

   Why do halogen boiling points rise from F₂ to I₂, Ren?

   • They become ionic
   • Larger molecules, stronger dispersion
   • They form more hydrogen bonds going down
10. 9.

    What makes dispersion attractions stronger, Tala?

    • More electrons in a larger molecule
    • Fewer electrons
    • A smaller molecule
11. 10.

    Which halogen is a solid at room temperature, Zee?

    • Chlorine
    • Fluorine
    • Iodine