Transcript Fusion and Fission - Bibb County Schools

Activities today
1. Bellwork
2. Fission/fusion Discussion
3. Think-peer share activity: Double-bubble
map on Fission-fusion
4. Note taking
5. Quiz
Fusion vs. fission
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.
A little bit on the atom…
Neutral neutrons
-
Nucleus
-
-
  

 

-
-
Negative electrons
Positive protons
Conservation of Energy/Mass
• Energy cannot be created
or destroyed – it can only
change form.
• E = mc2
• Mass is really a form of energy
Another look at E = mc2
• E = energy (J)
• m = mass (kg)
• c = speed of light (3 x 108 m/s)
• Mass is really just another form of energy!
FUSION AND FISSION
THE SUN
Nuclear Fusion
• Nuclear fusion is the process by
which multiple nuclei join together to
form a heavier nucleus.
• It is accompanied by the release or
absorption of energy depending on
the masses of the nuclei involved..
FUSION
NEUTRON
DEUTERIUM
HELIUM
TRITIUM
http://fusioned.gat.com
Complete the Reaction
1H
element
atomic number
(protons)
4Be
1H
6C
2He
1H
2He
1H
2He
6C
4Be
2He
8
2He
O
Fusion Changes Mass to Energy
E=mc2
.993 kg Helium
1kg Hydrogen
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.
Learning Check
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
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
Neutrons may:
1 - Cause another fission by colliding with a U235 nucleus
• Creates two smaller nuclides and free neutrons
• The free neutrons potentially collide with nearby U235 nuclei
• May cause the nuclide to split as well
Each split (fission) is
accompanied by a large
quantity of E-N-E-R-G-Y
2 - Be absorbed in other material
3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
How fusion can be used?
• GOOD
– A controlled reaction in a reactor used to
produce cleaner, inexpensive electricity???
• EVIL
– A fission bomb starts a fusion chain reaction
to create an incredibly powerful weapon –
thermonuclear weapons (H-bombs), MUCH
more destructive than atomic bombs.
A-bomb vs. H-bomb
• Atomic bomb (Hiroshima)– fission process
– Killed over 66,000 people instantly
– 13 kilotons of TNT-equivalent
– 2 exploded in warfare
• Hydrogen bomb – fusion process
– 10 megatons (million-tons) of TNT-equivalent
– NEVER exploded in warfare
– Is it the bomb too big to ever be used???
U.S. Electrical Power
Production by Source
Source: EIA
(2004)
Nuclear Fuel Costs
• Nuclear Fuel Costs Include
–
–
–
–
Uranium
Enrichment
Manufacturing
Waste Disposal
• Total Nuclear Fuel Cost is Only About 0.5 cents
per kilowatt-hour
– Uranium accounts for only about 20% of this cost or
0.1 cents per kilowatt-hour
– Increasing Uranium Cost has Minimal Impact
Review
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.
Fiss vs. Fuse
• Fiss = break down
• Start with a larger atom and finish with two
or more smaller atoms
• Fuse = build up
• Start with two smaller atoms and finish
with one larger atom
Review
• 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)
• Fission is a nuclear reaction in which a
heavy atomic nucleus is split into lighter
atomic nuclei
• Fusion is a nuclear reaction in which 2
light atomic nuclei are combined into a
single, heavier atomic nucleus
Mini-assessment
1. Which nuclear process produces large
amounts of energy?
A. Fission
B. Fusion
C. Both fission & fusion
D. Neither fission nor fusion
Mini-assessment
2. Fission is the process that _________
atomic nuclei.
A. Combines
B. Burns up
C. Stores
D. Splits
Mini-assessment
3. Mass may be converted into energy.
A. True
B. False
Mini-assessment
4. The fission process requires heavy
atomic nuclei.
A. True
B. False
Mini-assessment
5. Name a nuclear reaction that occurs
within the sun:
Mini-assessment
6. Fission is a natural process that occurs
on the planet Earth.
A. True
B. False
Mini-assessment
7. Explain this equation: (4 points)
E=
2
mc
8. Draw a Double Bubble Map of
Fusion and Fission
fission
fusion
Differences
Similarities
Differences
Cookie Fusion
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Procedure
Cut 2 squares of wax paper 10 cm on a side
Cut 5 cm wide slice of cookie dough (atom)
Find the mass of the atom and record on the table
Place the atom one cm away from the edge of a wax
paper square
Repeat step 2 thru 4 for a second atom
Place the atoms about 2 cm from each other
Place both atoms on a plate and microwave for 1 minute
Remove the “new element” and let cool for 2 minutes
Find the mass of the “new element”
Complete the table
Cookie Fusion
Mass Before
Cooking
Atom 1
Atom 2
Total
Difference
Mass After
Cooking