What are the two fissionable isotopes in common use?
Uranium-235 and Plutonium-239.
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What do most nuclear reactors use?
2-3% of Uranium-235
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Describe Nuclear fission
1.The nucleus of a fissionable isotope absorb a neutron 2. The nucleus splits into 2 smaller nuclei 3. 2 or 3 neutrons are emitted and energy is released. 4. A chain reaction occurs
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What is the energy release like in nuclear fission in comparison to chemical process?
Energy released in nuclear fission is much greater than burning
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What is a chain reaction?
When each fission event causes further fission events. In nuclear reactors these are controlled.
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What is nuclear fusion?
The process of forcing 2 nuclei close enough together so they form a single larger nucleus
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How can nuclear fusion be brought about?
By making two light nuclei collide at very high speed
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How is energy released form stars?
Nuclear fusion
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How can you overcome two nuclei approaching each other from repelling?
1. Reaction completed in high temperatures so they can overcome the repulsion and fuse. 2. High temperatures means reaction is contained by a magnetic field.
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What is the biggest source of background radiation?
Radon gas which seeps through the ground from radioactive subatnces in rocks deep underground
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What is the issue with radon gas?
Radon gas emits alpha particles which can cause a problem is breathed in.
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How can you reduce the exposure to nuclear radiations?
1. Keep as far as possible from sources of radiation 2. Spend as little as time exposed 3. Shield with materials such as conrete and lead.
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How do scientists believe planet earth came to being?
through the Big Bang around 13 billion years ago
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Describe the Big Bang
1. The universe was once a hot glowing ball of radiation 2. The nuclei of the lightest elements formed. 3. As the universe expanded the temperature fell 4. uncharged atoms were formed.
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Describe what the universe was like before stars and galaxies were formed
1. Dark patch cloud of hydrogen and helium 2. Dust and gas were pulled together by gravitational attraction 3.INtense heat caused nuclear fusion reactions in stars so they emitted visible light
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What are galaxies?
Very large groups of stars which are held by their own gravity.
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What is the first stage of the star life?
Gravitational forces pull clouds of dust and gas together to form a prostar
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What is the second stage of the life star?
The prostar becomes dense and the nuclei of light elements (hydrogen) fuse together. Energy is released makes the core of the star hotter and brighter
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Why are stars in the main sequence stable?
The inward gravity is balanced by the outward force of radiation from the core
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What happens to a star when it runs out of hydrogen nuclei?
It swells, cools down and turns red.
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Describe the life history from a low mass red giant
1. Low Mass Red Giant (sun) 2. Helium and light elements stop fusing and the star will contract into a white dwarf. 3. No more light emits and the star becomes a black dwarf
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Describe the life history from a high mass red supergiant
1. Swell to become a red supergiant 2. This continues to collapse 3. The star explode into a supernova 4. The core is left as neutron star 5. If massive enough, it becomes a black hole.
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How are chemical elements formed?
BY fusion processes in stars. Nuclei of lighter elements fuse to form nuclei of heavier elements, which releases large amounts of energy
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Why are elements heavier than iron formed in the final stages of the life of a big star?
Requires the input of energy and all elements get distributed through space by the supernova explosion.
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Heavier elements in the sun and inner planets prove what?
They were formed through debris scattered by a supernova.
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Other cards in this set
Card 2
Front
What are the two fissionable isotopes in common use?
Back
Uranium-235 and Plutonium-239.
Card 3
Front
What do most nuclear reactors use?
Back
Card 4
Front
Describe Nuclear fission
Back
Card 5
Front
What is the energy release like in nuclear fission in comparison to chemical process?
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