Transcript Fission and Fusion

Nuclear Reactions:
FISSION & FUSION
Introduction

Nuclear reactions deal with interactions
between the nuclei of atoms
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Both fission and fusion processes deal with
matter and energy
Matter and Energy
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Previous studies have taught us that “matter
and energy cannot be created nor destroyed”
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We now need to understand that Matter and
Energy are two forms of the same thing
E = mc2
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Remember that matter can be changed into
Energy
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This tells us that a small amount of mass can be
converted into a very large amount of energy
because the speed of light (c) is an extremely
large number
Energy
Mass
Light
Speed
Fission
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Fission may be defined as the process of
splitting an atomic nucleus into fission
fragments
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The fission fragments are generally in the form
of smaller atomic nuclei and neutrons
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Large amounts of energy are produced by the
fission process
Fission
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Fissile nuclei are generally atoms with more
neutrons than protons
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The nuclei of such heavy atoms are struck by
neutrons initiating the fission process
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Fission occurs when the strong nuclear force is
disrupted by an incoming projectile (in this
case a neutron)
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When the strong nuclear force is disrupted
electrostatic repulsion splits the nuclei
Fission
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A classic example of a fission reaction is that of
U-235:
U-235 + 1 Neutron
3 Neutrons + Kr-91 + Ba-142 + Energy
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In this example, a stray neutron strikes an atom of U-235.
It absorbs the neutron and becomes an unstable atom of
U-236. It then undergoes fission. Notice that more
neutrons are released in the reaction. These neutrons
can strike other U-235 atoms to initiate their fission.
Nuclear Chain Reaction
Fission
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Fission produces large amounts of heat energy
and it is this heat that is captured by nuclear
power plants to produce electricity.
Fusion
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Fusion is a nuclear reaction whereby two light
atomic nuclei fuse or combine to form a single
larger nuclei which is lighter than the sum of the
two that fuse.
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The lost mass is converted to energy. (E = mc2 )
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For fusion to occur, a large amount of energy is
needed to overcome the electrical charges of
the nuclei and fuse them together
Fusion
Fusion
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Fusion reactions do not occur naturally on our
planet but are the principal type of reaction
found in stars

The large masses, densities, and high
temperatures of stars provide the initial
energies needed to fuel fusion reactions
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The sun fuses hydrogen atoms to produce
helium, subatomic particles, and vast amounts
of energy
Energy Comparison
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Because of the large binding energies involved
in a nucleus, both fission and fusion involve
energy changes of more than a million times
larger than those energy changes associated
with chemical reactions.
Review
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Mass and Energy are two forms of the same
thing; neither can be created nor destroyed but
mass can be converted into energy (E = mc2)
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Fission is a nuclear reaction in which a heavy
atomic nucleus is split into lighter atomic nuclei
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Fusion is a nuclear reaction in which 2 light
atomic nuclei are combined into a single,
heavier atomic nucleus
Quiz
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Which nuclear process produces large
amounts of energy?
A. Fission
B. Fusion
C. Both fission & fusion
D. Neither fission nor fusion
Quiz
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Fission is the process that _________ atomic
nuclei.
A. Combines
B. Burns up
C. Stores
D. Splits
Quiz
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Mass may be converted into energy.
A. True
B. False
Quiz
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The fission process requires heavy
atomic nuclei.
A. True
B. False
Quiz

Name a nuclear reaction that occurs
within the sun:
Quiz
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Fission is a natural process that occurs
on the planet Earth.
A. True
B. False
Quiz

Explain this equation:
E = mc2