atomic structure 2014 - mrs. sjuts' science...
TRANSCRIPT
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KEY TERMS: Ch 9.4 Nuclear Reactions
• Nuclear Fission – the process of splitting a nucleus into two nuclei with smaller masses
• Chain reaction – ongoing series of fission reactions • Critical mass – the amount of fissionable material required so that each fission reaction produce approximately one more fission reaction
• Nuclear Fusion – two nuclei with low masses are combined to form one nucleus of larger mass
• Fission and Fusion Video
Nuclear Fission • Fission means “to divide” • The process of splitting a nucleus into two nuclei
with smaller masses • This occurs when a neutron hits the nucleus of an atom
• Only large nuclei can underdo fission reactions • Two uses from book: generate electricity, nuclear
weapons • The total mass of the products is slightly less than the
mass of the original nuclear and the neutrons that break free • The missing mass is converted into large amounts of
energy
Nuclear Fission
Neutron Uranium - 235
Lighter element
Lighter element
Neutrons + Energy
Nuclear Fission • Chain reactions are continuing series of reactions in which each
produces a product that can react again • If chain reaction occurs too quickly, explosions occur, releasing a lot
of energy all at once
energy
energy
energy
energy
energy
energy
Fission of Uranium-238
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Nuclear Fusion • Fusion = combine • Nuclear Fusion is when two or more nuclei combine to
form a larger nucleus (requires very high temps to overcome the repulsive forces)
• The sun uses this process to produce energy • It fuses hydrogen into helium • The problem lies in the energy involved to start fusion • Most nuclei that can undergo fusion are fairly unreactive • Energy given off (output) does not outweigh the energy needed
(input)
• Hydrogen Bomb • Just like in fission, a small amount of mass is converted
into a large amount of energy
Fusion of Hydrogen into helium
Nuclear Fusion
energy
energy
neutrino
positron
neutrino
positron
Energy to Mass Conversions • Think back to the law of conservation of energy • We need to include mass in this law when talking
about fission and fusions reactions • This relationship is shown by Einstein’s theory of
relativity • This states that energy and mass are equivalent and
can be converted using the equation E=mc2
Warm-Up 1. What type of nuclear reaction shown below? 2. Write an equation for the reaction. You only need to
include the symbol and mass number.
3. What type of nuclear reaction is shown below?