1. Nuclear Chemistry III. Fission & Fusion (Nuclear reactions that are NOT radioactive decay.) III. Fission & Fusion (Nuclear reactions that are NOT radioactive decay.)

2. A. F ission  Splitting a large (heavy) nucleus into two or more smaller nuclei.  Neutrons are always involved! Neutron bombardment causes fission. (Fission = splitting) Neutrons are also products of fission.  1 g of fission fuel = 3 tons of coal

3. A. F ission  Chain Reaction = self-propagating fission rxn Propagated by 1 n Free neutrons cause fission Each fission makes more Which sets off more fission! Making more Repeat ad infinitum!

4. A. F ission  Critical Mass = minimum mass required to sustain a chain reaction Chain reaction requires a certain “concentration” of fission fuel nearby. Otherwise the neutrons don’t get enough chances to keep things going.

5. B. Fusion  Joining two small (light) nuclei into one larger nucleus.  Parent nuclides collide at extremely high velocity  Forming one daughter nuclide with greater mass.  Neutrons are usually released to stabilize the daughter nuclide. Ejecting neutrons corrects the p:n ratio.

6. B. Fusion  Thermonuclear:  A temperature of 40,000,000 K is needed to sustain hydrogen fusion!  At normal temperatures the two parent atoms would just make a chemical bond. (Their nuclei would never interact at all.)  Fusion is even more energy efficient than fission:  1 g of fusion fuel = 20 tons of coal

7. B. Fusion  Fusion occurs naturally in stars.  Our sun is fusing hydrogen into helium right now–fusion reactions generate the heat and light of stars.  Supergiant stars fuse even larger nuclei After fusing H into He, the He is fused, then successive elements. All atoms other than 1 H were created by fusion in a supergiant star.

8. C. Johannesson C. Fission vs. Fusion  235 U is limited  danger of meltdown  toxic waste  thermal pollution  fuel is abundant  no danger of meltdown  no toxic waste  not yet sustainable FISSIONFISSION FUSIONFUSION

9. Which reaction type? Less Energy More Energy