fission & fusion movie - mrs. hayden,...
TRANSCRIPT
Fission & Fusion
Movie
Matter and Energy
• Previous studies have taught us that
“matter and energy cannot be created
nor destroyed”
• We balance equations to obey this law.
– 2 H2O 2 H2 + O2
• We now need to understand that Matter
and Energy are two forms of the same
thing
Mass
• Matter can be changed into Energy
• Einstein’s formula above tells us how the change occurs
• In the equation above:
E = Energy
m = Mass
c = Speed of Light (Universal Constant)
Energy Light
Speed
E = mc2
E = mc2
• The equation may be read as follows:
Energy (E) is equal to Mass (m) multiplied by
the Speed of Light (c) squared
• 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
• Fusion is a nuclear reaction whereby two light
atomic nuclei fuse or combine to form a single
larger, heavier nucleus
• The fusion process generates tremendous
amounts energy
• For fusion to occur, a LARGE amount of
energy is needed to overcome the electrical
charges of the nuclei and fuse them together
Fusion
OUR STAR
How do stars produce energy?
• Stars are mostly
Hydrogen that
produce energy by
fusion of hydrogen
nuclei
• 2 protons (H-1) fuse
to make a H isotope
(H-2); then H-1 + H-2
form an isotope of
He-3.
The emission of a positron or a positive electron is referred
to as beta decay. The positron is accompanied by a
neutrino, a massless and chargeless particle. Positrons
are emitted with the same kind of energy spectrum as
electrons in negative beta decay because of the emission
of the neutrino.
Light
light neutrino
positron
How do stars produce energy?
• Finally 4 hydrogen
nuclei combine
into 1 Helium
nucleus.
• A small amount of
matter changes
into a huge
amount of energy.
Fusion
• 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
• The sun fuses hydrogen atoms to produce
helium, subatomic particles, and vast amounts of
energy
FUSION
DEUTERIUM
TRITIUM
HELIUM
NEUTRON
http://fusioned.gat.com
Complete the Reaction
1H
4Be
1H
8O
4Be
2He
2He
1H
2He
2He
2He
6C
1H element atomic number
(protons)
6C
Learning Check
What process creates energy in the Sun? Fusion of hydrogen into helium in the Sun’s core
generates the Sun’s energy.
How long ago did fusion generate the energy we now receive as sunlight?
Fusion created the energy we receive today about a million years ago. This is the time it takes for photons and then convection to transport energy through the solar interior to the photosphere. Once sunlight emerges from the photosphere, it takes only about 8 minutes to reach Earth.
NUCLEAR FISSION
A reaction in which an atomic
nucleus of a radioactive element
splits by bombardment from an
external source, with
simultaneous release of large
amounts of energy, used for
electric power generation
Fission
• Fission may be defined as the process of
splitting an atomic nucleus into fission
fragments
• The fission fragments are generally in the
form of smaller atomic nuclei and neutrons
• Large amounts of energy are produced by
the fission process
What nuclei can split during
nuclear fission?
• Only large nuclei
like U or plutonium
can split apart
during nuclear
fission.
Click on image
for animation
Chain Reaction
• Free neutrons produced by fission can hit
other nuclei emitting more neutrons
repeating the reaction over and over.
• A series of fission reactions is called a
chain reaction.
• Can only be slowed by using materials
that will absorb the neutrons.
• Chain Reaction Video
• pHet annimation
Nuclear Fission
Neutron induced in U235
Fission is Exothermic
The sum of the masses of
the resulting nuclei is less
than the original mass
(about 0.1% less)
The “missing mass” is converted
to energy according to E=mc2
Review Movie
Nuclear fission:
A large nucleus splits into several
small nuclei when impacted by a
neutron, and energy is released in
this process
Nuclear fusion:
Several small nuclei fuse
together and release
energy.