5.3.4 NUCLEAR FISSION AND FUSION

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Describe Einsteins mass-energy equation
mass of isotope/ particle is less than individual masses of nucleons/
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What is binding energy?what is it measured in?
energy equivalent to the mass defect of a nucleus/ min energy required to separate to infinity all the nucleons in a nucleus/ MeV
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What is binding energy per nucleon?
min energy required to completely separate nucleons of a nucleus divided by the total number of nucleons
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Describe the binding energy per nucleon vs nucleon number graph
high bonding energy per nucleon means more energy needed/ most stable nuclei at max point/ fusion as bottom and fission at top
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What is fission?
equal splitting of large unstable nuclei into smaller more stable nuclei with a higher binding energy per nucleon
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What is fusion?
joining of smaller nuclei into stable bigger ones/ mass decrease transformed into NRG/ high temp 10'7K/ high pressures/ high temps
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Describe induced nuclear fission
split into two nuclei of approx same mass/ absorption of a neutron deforms the nuclei into a dumbbell shape/ electrostatic repulsion between the protons in the two halves are greater than the short ranged forces
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Describe the nuclear chain reaction
occurs when one nuclear reaction causes av of one or more nuclear reactions - self propagating series of reactions/ slow moving neutrons have greater chance of causing fission
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Describe the structure of fission reactors
fuel rods - contain uranium nuclei inserted into core/ control rods - neutron absorbing material/ moderator - reduces speed of fast moving neutrons
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How is the nuclear chain reaction controlled?
control rods are inserted so as to allow one neutron from previous reaction to begin the next, control n of neutrons/ chain reaction must be critical where rate at which neutrons produced = rate at which made
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What are the advantages of nuclear fission as an energy source?
peaceful source - creates energy/ does not cause acid rain or waste gases that causes pollution/ energy for nuclear power - provide elecrivity
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What are the disadvantages of nuclei fission as an energy source?
risks of radiation/ long half life of waste - radioactive for long time and ionising/ can be used to drive nuclear weapons (non controlled chain reaction)
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Why are high temperatures needed in nuclear fusion?
some of the fast moving protons come close enough of the strong nuclear force to overcome the electrostatic repulsion
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Describe the conditions in the core of stars
protons/hydrogen nuclei fuse to produce helium/ decrease in mass hence energy released/ mixture of free nuclei - plasma
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Card 2

Front

What is binding energy?what is it measured in?

Back

energy equivalent to the mass defect of a nucleus/ min energy required to separate to infinity all the nucleons in a nucleus/ MeV

Card 3

Front

What is binding energy per nucleon?

Back

Preview of the front of card 3

Card 4

Front

Describe the binding energy per nucleon vs nucleon number graph

Back

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Card 5

Front

What is fission?

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