3.3 Nuclear Reactions and Forces

What was the 19th-century scientific theory for the Sun's energy, before the understanding of atomic structure?

• Chemical reactions

• Nuclear fusion

• Gravitational collapse

• Electromagnetic radiation

What force is responsible for holding the nucleus of an atom together, despite the repulsion between positively charged protons?

• Electromagnetic force

• Gravitational force

• Nuclear force

• Van der Waals force

What happens to an atomic nucleus if it contains too many protons or too many neutrons?

• It becomes a different element.

• It becomes more stable.

• It falls apart.

• It attracts more particles.

What extreme conditions are necessary for atomic nuclei to overcome their natural repulsion and undergo nuclear reactions?

• Extreme cold and low pressure

• Extreme heat and low pressure

• Extreme cold and high pressure

• Extreme heat and high pressure

How does the energy released in a nuclear reaction compare to that released in a chemical reaction?

• Nuclear reactions release slightly less energy.

• Nuclear reactions release significantly more energy.

• Both release similar amounts of energy.

• Chemical reactions release more energy.

What is a characteristic of the weak nuclear force?

• It holds the nucleus together.

• It acts quickly.

• It causes protons and neutrons to switch identities.

• It is responsible for nuclear fusion in the Sun.

What happens to a free neutron when it undergoes beta decay?

• It gains mass and turns into a proton.

• It loses mass and turns into a proton.

• It turns into an electron.

• It remains a neutron but releases energy.

How long does it take for half of a sample of Uranium-235 atoms to decay into Lead?

• A few seconds

• Approximately 400 years

• About 700 million years

• 1 billion years

What is the product of the first step in the nuclear fusion process that powers the Sun?

• Helium-3

• Helium-4

• Deuterium (Hydrogen-2)

• A free neutron

Which step in the Sun's nuclear fusion process is the slowest?

• The formation of Helium-3 from Deuterium and a proton.

• The formation of Helium-4 from two Helium-3 nuclei.

• The formation of Deuterium from two protons.

• All steps occur at roughly the same speed.