Energy from the nucleus Flashcards
Nuclear fission
The process in which uranium-235 and plutonium -239 split into two fragments, releasing energy and two or three neutrons as a result
Chain reaction
Reactions in which one reaction causes further reactions. A nuclear chain reaction occurs when fission neutrons cause further fission
Nuclear fusion
The process in which small nuclei are forced together so they fuse with each other to form a larger nucleus
Gravitational attraction
The force that pulls masses together
Star
A large ball of gas in space that emits radiation
Galaxy
A collection of billions of stars, held together by their own gravity
Protostar
The concentration of dust clouds and gas in space that forms a star
Main sequence star
The main stage in the life of a star, during which it radiates energy because of fusion of hydrogen nuclei in its core
Red giant
A star that has expanded and cooled, resulting in it becoming red and much larger than it was before it expanded
White dwarf
A star that has collapsed from the red giant stage to become much hotter and denser than it was
Black dwarf
A star that has faded out and gone cold
Supergiant
A massive star that becomes much larger than a giant star when fusion of helium nuclei commences
Supernova
The explosion of a massive star after fusion in its core ceases and the matter surrounding its core collapses on to the core and rebounds
Neutron star
The highly compressed core of a massive star that remains after a supernova explosion
Black hole
An object in space that has so much mass that nothing, not even light, can escape from its gravitational field
What is nuclear fission?
Nuclear fission is the splitting of a nucleus into two approximately equal fragments and the release of two or three neutrons
Which radioactive isotopes undergo fission?
Uranium-235 and plutonium-239
What is a chain reaction?
A chain reaction occurs in a nuclear reaction when each fission event causes further fission events
How is a chain reaction in a nuclear reactor controlled?
In a nuclear reactor, control rods absorb fission neutrons to ensure that, on average, only one neutron per fission goes on to produce further fission
What is nuclear fusion?
Nuclear fusion is the process of forcing two nuclei close enough together so they form a single larger nucleus
How can nuclei be made to fuse together?
Nuclear fusion can be brought about by making two light nuclei collide at very high speed
Where does the Sun’s energy come from?
Energy is released when two light nuclei are fused together. Nuclear fusion in the Sun’s core releases energy
Why is it difficult to make a nuclear fusion reactor?
A fusion reactor needs to be at a very high temperature before nuclear fusion can take place. The nuclei to be fused are difficult to contain
What is radon gas and why is it dangerous?
Radon gas is an α-emitting isotope that seeps into houses in certain areas through the ground
How safe are nuclear reactors?
There are thousands of fission reactors safely in use in the world, and none of them are of the same type as the Chernobyl reactors that exploded
What happens to nuclear waste?
Nuclear waste is stored in safe and secure conditions for many years after unused uranium and plutonium (to be used in the future) is removed from it
What was the universe like in the billions of years before stars and galaxies were formed?
Before galaxies and stars were formed, the universe was a dark patchy cloud of hydrogen and helium
What is the force responsible for the formation of stars and galaxies?
The force of gravity pulled matter into galaxies and stars
What are the stages in the life of a low mass star?
protostar → main sequence star → red giant → white dwarf → black dwarf
What are the stages in the life of a high mass star?
protostar → main sequence star → red supergiant → supernova → neutron star → black hole (if sufficient mass)
What will eventually happen to the Sun?
The Sun will eventually become a black dwarf
What is a supernova?
A supernova is the explosion of a supergiant after it collapses
What chemical elements are formed inside stars?
Elements as heavy as iron are formed inside stars as a result of nuclear fusion
What chemical elements are formed in supernovae?
Elements heavier than iron are formed in supernovae supernovae, as well as light elements
Why does the Earth contain heavy elements?
The Sun and the rest of the Solar System were formed from the debris of a supernova
