The Sun's layers and the fusion that powers it

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Power about 3.8 × 10^26 W; c² ≈ 9.0 × 10^16 m²/s². The Sun gives off about 3.8 × 10^26 W (IAU). With E = mc² and c² ≈ 9.0 × 10^16 m²/s², about how much mass becomes energy each second, by Esme's math?

   • About 4 billion metric tons
   • Zero, since mass is conserved
   • About 4 kilograms
   • About 4 million metric tons
2. 2.

   Fusion turns about 0.7% of hydrogen's mass into energy. If 1 kg of hydrogen fuses into helium, about how much mass becomes energy, by Jun's math?

   • About 7 g
   • 0 g, since mass is conserved
   • About 70 g
   • About 0.7 g
3. 3.

   Luz's friend says the Sun is a giant ball of burning gas, like a campfire. Which response is best?

   • Agree: the Sun burns hydrogen with oxygen
   • Disagree: the Sun runs on fission of uranium
   • Disagree: its energy comes from nuclear fusion in the core
   • Agree: fire and fusion are the same process
4. 4.

   A path from the core labeled about 170,000 years, then to Earth labeled about 8 minutes. Milo's cousin says the energy in today's sunlight was released in the core just 8 minutes ago. Which response is best (NASA)?

   • Disagree: it was released 8 hours ago
   • Disagree: it took about 170,000 years to leave the Sun first
   • Agree: the radiative zone is empty space
   • Agree: light leaves the core at once
5. 5.

   Noah's friend says the Sun's surface must be its hottest part, since that is where the light comes from. Which response is best?

   • Agree: light comes from the hottest part
   • Agree: the core is cold and dark
   • Disagree: the 15 million °C core is far hotter
   • Disagree: the convection zone is the hottest part

6. Read this first

   Sun temperatures (NASA)

   Layer	Temperature
   core	about 15 million °C
   photosphere	about 5,500 °C

7. 6.

   Using kelvins (°C + 273), about how many times hotter is the Sun's core (15 million °C) than its photosphere (5,500 °C), by Pia's math?

   • The photosphere is the hotter one
   • About 2,700 times
   • About 2,600 times
   • About 3 times

8. Sun surface temperature

   Source	Value
   H-R card	about 5,800 K
   NASA	about 5,500 °C

9. 7.

   The H-R card puts the Sun at about 5,800 K, and NASA lists its surface at about 5,500 °C. Do they agree, by Tala's math?

   • Yes: 5,500 + 273 is about 5,800 K
   • No: 5,800 K must be the core temperature
   • No: they differ by 300 degrees
   • Yes: kelvins and degrees Celsius are the same numbers
10. 8.

    Why does fusion need the core's temperature of about 15 million °C, by Zee's reading?

    • Fusion needs oxygen, which only the core has
    • Heat splits helium back into hydrogen
    • Heat lights the hydrogen, as a match lights wood
    • Positive nuclei repel; only very fast ones get close enough to fuse
11. 9.

    Core density about 150 g/cm³. NASA gives the core's density as about 150 g/cm³. Why does such high density help fusion, by Ari's reading?

    • Dense matter burns for longer
    • High density splits nuclei apart
    • High density lets light escape the core at once
    • Packed nuclei collide more often
12. 10.

    What keeps the Sun from collapsing under its own gravity, by Bo's reading (NASA)?

    • Fission blasts push it apart
    • Burning gases push outward like exhaust from a rocket engine
    • Outward pressure from fusion-heated gas balances gravity
    • Nothing; the Sun is collapsing quickly