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