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?

   • Zero, since mass is conserved
   • About 4 kilograms
   • About 4 billion metric tons
   • 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 0.7 g
   • 0 g, since mass is conserved
   • About 7 g
   • About 70 g
3. 3.

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

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

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

5. Read this first

   Sun temperatures (NASA)

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

6. 5.

   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?

   • About 2,700 times
   • About 3 times
   • About 2,600 times
   • The photosphere is the hotter one
7. 6.

   NASA lists the photosphere at about 5,500 °C and the corona, the Sun's outer atmosphere, at up to 2 million °C. Which statement is true, by Ren's reading?

   • The photosphere is the hottest layer outside the core
   • The corona is where fusion happens
   • The corona is far hotter than the photosphere
   • The corona is cooler, since it is farther from the core

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

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

    • Heat lights the hydrogen, as a match lights wood
    • Positive nuclei repel; only very fast ones get close enough to fuse
    • Heat splits helium back into hydrogen
    • Fusion needs oxygen, which only the core has
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
    • Nothing; the Sun is collapsing quickly
    • Outward pressure from fusion-heated gas balances gravity