Question

alternate video 1

• what is fusion?
• what kind of temperature is required for fusion to occur?
• write the fusion equation for deuterium and tritium.
• what problems do scientists run into when trying to harness the power of fusion?
• what is fission?
• what are two fissile materials?
• what is a chain reaction?
• how do we control fission in nuclear power plants?

alternate video 2

• what is a star mostly made of when it is first formed?
• what does a star make for 90% of its life?
• what happens when a star runs out of hydrogen?
• name some of the first elements that form in a star after it runs out of hydrogen.
• what element marks the “end of the road” for a star? what happens next?
• what elements form during a supernova?

Explanation:

Step1: Define fusion

Fusion is the process where two light - nuclei combine to form a heavier nucleus, releasing a large amount of energy.

Step2: Temperature for fusion

Fusion requires extremely high temperatures (millions of degrees Celsius) to overcome the electrostatic repulsion between positively - charged nuclei.

Step3: Deuterium - tritium fusion equation

The fusion equation for deuterium ($_1^2H$) and tritium ($_1^3H$) is: $_1^2H+_1^3H
ightarrow_2^4He + _0^1n$.

Step4: Problems in harnessing fusion

Problems include containing the high - temperature plasma (as no material can withstand the temperatures), achieving and maintaining the necessary conditions for a sustained reaction.

Step5: Define fission

Fission is the splitting of a heavy nucleus into two or more lighter nuclei, also releasing energy.

Step6: Fissile materials

Two fissile materials are uranium - 235 ($^{235}U$) and plutonium - 239 ($^{239}Pu$).

Step7: Chain reaction

A chain reaction in fission occurs when neutrons released by a fission event cause other nuclei to fission, creating a self - sustaining reaction.

Step8: Controlling fission in nuclear power plants

In nuclear power plants, control rods (made of materials like boron or cadmium) are used to absorb excess neutrons and control the rate of the fission chain reaction.

Step9: Star composition at first formation

A star is mostly made of hydrogen when it is first formed.

Step10: Star's activity for 90% of life

For 90% of its life, a star fuses hydrogen into helium in its core.

Step11: After hydrogen runs out

After a star runs out of hydrogen, elements like helium, carbon, oxygen, etc. start to form through further fusion reactions.

Step12: End - of - life element for a star

Iron marks the "end of the road" for a star. Once iron is formed in the core, further fusion requires energy input rather than releasing it.

Step13: What happens after iron formation

After iron formation, the core collapses, leading to a supernova explosion.

Step14: Elements formed in a supernova

Elements heavier than iron, such as gold, silver, uranium, etc., are formed during a supernova.

Answer:

Fusion is the combination of light - nuclei releasing energy. High temperatures are needed for fusion. Deuterium - tritium fusion: $_1^2H+_1^3H
ightarrow_2^4He + _0^1n$. Problems in harnessing fusion are plasma containment and reaction sustenance. Fission is nucleus splitting. Fissile materials: uranium - 235 and plutonium - 239. Chain reaction: neutrons cause more fissions. Control in nuclear power plants: control rods absorb neutrons. Star is mostly hydrogen at first. For 90% of life, it fuses hydrogen to helium. After hydrogen, other elements form. Iron marks end, then core collapse and supernova. Supernova forms heavy elements.