IS2 EXAM REVIEW

True/False: The Sun is the closest star to Earth.

What is the Sun primarily composed of by mass?

• Hydrogen and Oxygen

• Hydrogen and Helium

• Carbon and Helium

• Hydrogen and Nitrogen

Multiple Choice: What process in the Sun generates energy?

• Fission of helium

• Fusion of hydrogen into helium

• Combustion of gases

• Decay of radioactive elements

What is the diameter of the Sun compared to the Earth?

Answer explanation

The sun's diameter is about 109 times larger than the earth's

How long does it take for sunlight to reach Earth?

Answer explanation

It would take roughly 8 minutes and 20 seconds.

True/False: The Sun's energy comes from the fission of hydrogen.

Answer explanation

False. The Sun's energy comes from hydrogen fusion, not fission.

Review:
Nuclear fusion - process where atomic nuclei combine to form a heavier nucleus, releasing energy in the process.
Nuclear fission - opposite process, where a heavy nucleus splits into lighter nuclei, releasing energy.

What is the average temperature in the core of the Sun?

Answer explanation

Approximately 15 million degrees celcius.

Describe the proton-proton chain reaction in the Sun.

Answer explanation

The proton-proton chain reaction is a process by which hydrogen nuclei (protons) fuse to form helium, releasing energy in the form of light and heat.

Steps
1. Proton-Proton Fusion: Two protons collide and fuse to form a deuteron (a nucleus containing one proton and one neutron), releasing a positron (a positively charged electron) and a neutrino.

• 2. Deuteron-Proton Fusion: A deuteron collides with another proton to form a helium-3 nucleus (containing two protons and one neutron), releasing a gamma ray.

• 3. Helium-3 Fusion: Two helium-3 nuclei collide to form a helium-4 nucleus (containing two protons and two neutrons), releasing two protons.

Multiple Choice: Which particles are involved in the first step of the proton-proton chain reaction?

• Electrons and neutrons

• Protons and positrons

• Protons only

• Neutrinos and photons

What is the name of the force that allows protons to overcome repulsion in the Sun's core?

Answer explanation

Strong nuclear force

In the Sun's core, the extremely high temperature and pressure bring protons close enough together for the strong nuclear force to overcome the electromagnetic repulsion and allow fusion to occur. This process releases a tremendous amount of energy in the form of light and heat, powering the Sun and ultimately sustaining life on Earth.