Post on 27-Mar-2015
Activities today1. 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…
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Negative electronsPositive protons
Neutral neutrons
Nucleus
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
Every second, the sun converts 500 million metric tons of hydrogen to helium. Due to the process of fusion, 5 million metric tons of excess material is converted into energy in each second. This means that every year, 157,680,000,000,000 metric tons are converted into energy.
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
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
Fusion Changes Mass to EnergyE=mc2
H
He
1kg Hydrogen
.993 kg Helium
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
2 - Be absorbed in other material
3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y
• Creates two smaller nuclides and free neutrons• The free neutrons potentially collide with nearby U235 nuclei• May cause the nuclide to split as well
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
• Mass and Energy are two forms of the Mass and Energy are two forms of the same thing; neither can be created nor same thing; neither can be created nor destroyed but mass can be converted destroyed but mass can be converted into energy (E = mcinto energy (E = mc22))
• Fission is a nuclear reaction in which a Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter heavy atomic nucleus is split into lighter atomic nucleiatomic nuclei
• Fusion is a nuclear reaction in which 2 Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a light atomic nuclei are combined into a single, heavier atomic nucleussingle, heavier atomic nucleus
Review
Mini-assessment
1. Which nuclear process produces large 1. Which nuclear process produces large amounts of energy?amounts of energy?
A. FissionA. Fission
B. FusionB. Fusion
C. Both fission & fusionC. Both fission & fusion
D. Neither fission nor fusionD. Neither fission nor fusion
2. Fission is the process that _________ 2. Fission is the process that _________ atomic nuclei.atomic nuclei.
A. CombinesA. Combines
B. Burns upB. Burns up
C. StoresC. Stores
D. SplitsD. Splits
Mini-assessment
3. Mass may be converted into energy.3. Mass may be converted into energy.
A. TrueA. True
B. FalseB. False
Mini-assessment
4. The fission process requires heavy 4. The fission process requires heavy atomic nuclei.atomic nuclei.
A. TrueA. True
B. FalseB. False
Mini-assessment
5. Name a nuclear reaction that occurs 5. Name a nuclear reaction that occurs within the sun:within the sun:
Mini-assessment
6. Fission is a natural process that occurs 6. Fission is a natural process that occurs on the planet Earth.on the planet Earth.
A. TrueA. True
B. FalseB. False
Mini-assessment
7. Explain this equation: (4 points)7. Explain this equation: (4 points)
E = mcE = mc22
Mini-assessment
8. Draw a Double Bubble Map of Fusion and Fission
fusion fission
Differences Similarities Differences
Cookie Fusion
• 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
Mass After Cooking
Atom 1
Atom 2
Total
Difference