Activities today Bellwork Fission/fusion Discussion Think-peer share activity: Double-bubble map on Fission-fusion Note taking 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. 2

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 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.

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 NEUTRON HELIUM TRITIUM http://fusioned.gat.com

Complete the Reaction 4Be 1H element 4Be 2He 6C 2He 2He 6C 8O 2He atomic number (protons) 4Be 1H 2He 6C 2He 1H 1H 6C 2He 4Be 8O 2He 2He

Fusion Changes Mass to Energy E=mc2 .993 kg Helium He H 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 2 - Be absorbed in other material 3 - Lost in the system If sufficient neutrons are present, we may achieve a chain reaction 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

How fusion can be used? GOOD EVIL 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 The United States has 103 nuclear power reactors in 31 states. Nuclear energy provides electricity for one of every five homes and business … the second-largest source of electricity after coal. Some states are clearly are more dependent on nuclear energy than others. Vermont gets 76 percent of its electricity from nuclear reactors … New Hampshire, 58 percent … and South Carolina, 55 percent. In Virginia, nuclear power provides more than 40 percent of the electricity used. 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 = mc2

8. Draw a Double Bubble Map of Fusion and 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