P2.6 Nuclear fission and nuclear fusion Flashcards
What are the most commonly used substances in nuclear fission?
Uranium-235 and Plutonium-239
What is nuclear fission?
The splitting of an atomic nucleus
For fission to occur, what must the uranium and plutonium do first?
Absorb a neutron
What happens in nuclear fission?
A neutron is fired at the neutron. The neutron then splits into two smaller nuclei and two or three neutrons and energy are released. These neutrons released then go on to hit more nuclei which then split and so on
What is nuclear fission?
A controlled chain reaction
What is an example of an uncontrolled chain reaction?
A nuclear bomb
What is nuclear fusion?
The joining of two atomic nuclei to from a larger one
What is nuclear fusion the process of?
How energy is released from stars
How do stars form?
When enough dust and gas from space is pulled together by gravitational attraction
How may planets form?
Smaller masses may form and be attracted to a larger mass and become a planet
Why did the early universe only consist of hydrogen but now a large variety of other elements?
During most of a stars lifetime hydrogen is fused to form helium. When the star runs out of hydrogen, other fusion reactions take place forming other elements. Elements up to iron are formed, and elements heavier than iron are formed in supernovas
During the main sequence period of a star’s lifecycle it is stable, why?
Because the forces within it are balanced
What is the star’s life cycle determine by?
Its size
What does a protostar turn into?
A main sequence star
What does a star about the same size as the sun turn into after being a main sequence star?
It expands to become red giant
What does a red giant turn into?
It shrinks to become a white dwarf
What does a white dwarf become?
It cools to become a black dwarf
What does a star much bigger than the sun turn into after being a main sequence star?
It expands to become a red super giant
What happens to a red super giant when it becomes unstable?
It collapses in on itself and then explodes massively, this is a supernova
What is left behind after a supernova?
Either the collapsed core of the star is left in the form of a neutron star or a black hole
Fusion in stars produces all…
The naturally occurring elements
How may the elements be distributed throughout the universe?
By the explosion of a massive star, supernova, at the end of its life
Elements up to iron are formed in the…
Stable period of a star
Elements heavier than iron are formed in…
A supernova
Stars are able to maintain their energy output for…
Millions of years
