1. Slide 1 of 20 Chemistry 25.3

2. © Copyright Pearson Prentice Hall Slide 2 of 20 Fission and Fusion of Atomic Nuclei The sun is not actually burning. If the energy given off by the sun were the product of a combustion reaction, the sun would have burned out approximately 2000 years after it was formed, long before today. You will learn how energy is produced in the sun. 25.3

3. © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Slide 3 of 20 Nuclear Fission What happens in a nuclear chain reaction? 25.3

4. Slide 4 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Fission When the nuclei of certain isotopes are bombarded with neutrons, they undergo fission, the splitting of a nucleus into smaller fragments. 25.3

5. © Copyright Pearson Prentice Hall Slide 5 of 20 Fission and Fusion of Atomic Nuclei > Nuclear Fission In a chain reaction, some of the neutrons produced react with other fissionable atoms, producing more neutrons which react with still more fissionable atoms. 25.3

6. © Copyright Pearson Prentice Hall Slide 6 of 20 Fission and Fusion of Atomic Nuclei > Nuclear Fission 25.3

7. Slide 7 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Fission 25.3 A Nuclear Power Plant

8. Slide 8 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Fission Neutron Moderation Neutron moderation is a process that slows down neutrons so the reactor fuel (uranium-235 or plutonium-239) captures them to continue the chain reaction. 25.3

9. Slide 9 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Fission Neutron Absorption Neutron absorption is a process that decreases the number of slow-moving neutrons. Control rods, made of a material such a cadmium, are used to absorb neutrons. 25.3

10. © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Slide 10 of 20 Nuclear Waste Why are spent fuel rods from a nuclear reaction stored in water? 25.3

11. Slide 11 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Waste Water cools the spent rods, and also acts as a radiation shield to reduce the radiation levels. 25.3

12. © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Slide 12 of 20 Nuclear Fusion How do fission reactions and fusion reactions differ? 25.3

13. Slide 13 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Fusion Fusion occurs when nuclei combine to produce a nucleus of greater mass. In solar fusion, hydrogen nuclei (protons) fuse to make helium nuclei and two positrons. 25.3

14. © Copyright Pearson Prentice Hall Slide 14 of 20 Fission and Fusion of Atomic Nuclei > Nuclear Fusion Fusion reactions, in which small nuclei combine, release much more energy than fission reactions, in which large nuclei split. 25.3

15. Slide 15 of 20 © Copyright Pearson Prentice Hall Fission and Fusion of Atomic Nuclei > Nuclear Fusion The use of controlled fusion as an energy source on Earth is appealing. The potential fuels are inexpensive and readily available. The problems with fusion lie in achieving the high temperatures necessary to start the reaction and in containing the reaction once it has started. 25.3

16. © Copyright Pearson Prentice Hall Slide 16 of 20 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 25.3 Section Quiz. 25.3.

17. © Copyright Pearson Prentice Hall Slide 17 of 20 25.3 Section Quiz. 1.One of the control mechanisms for a sustainable nuclear chain reactor involves slowing down the released neutrons so they may be captured by other nuclei. This is done using a.moderators. b.shielding. c.absorbers. d.control rods.

18. © Copyright Pearson Prentice Hall Slide 18 of 20 25.3 Section Quiz. 2.Spent fuel rods are stored in a.lead-lined containers. b.deep pools of water. c.thick concrete bunkers. d.cadmium or graphite containers.

19. © Copyright Pearson Prentice Hall Slide 19 of 20 25.3 Section Quiz. 3.Choose the correct words for the spaces. In solar fusion, _______ nuclei fuse to form _______ nuclei. a.helium, hydrogen b.hydrogen-1, hydrogen-2 c.hydrogen, helium d.hydrogen-1, hydrogen-3

20. © Copyright Pearson Prentice Hall Slide 20 of 20 Chemistry 25.4

21. © Copyright Pearson Prentice Hall Slide 21 of 20 Radiation in Your Life In a smoke detector, radiation from the Americum nuclei ionizes the nitrogen and oxygen in smoke-free air, allowing a current to flow. When smoke particles get in the way, a drop in current is detected by an electronic circuit, causing it to sound an alarm. You will learn about some of the other practical uses of radiation. 25.4

22. © Copyright Pearson Prentice Hall Slide 22 of 20 Detecting Radiation What are three devices used to detect radiation? 25.4

23. © Copyright Pearson Prentice Hall Slide 23 of 20 Detecting Radiation a.Ionizing radiation is radiation with enough energy to knock electrons off some atoms of the bombarded substance to produce ions. Devices such as Geiger counters, scintillation counters, and film badges are commonly used to detect radiation. 25.4

24. © Copyright Pearson Prentice Hall Slide 24 of 20 Detecting Radiation a.Radiation can produce ions, which can then be detected, or it can expose a photographic plate and produce images. 25.4

25. © Copyright Pearson Prentice Hall Slide 25 of 20 Detecting Radiation Geiger Counter a.A Geiger counter uses a gas-filled metal tube to detect radiation. 25.4

26. © Copyright Pearson Prentice Hall Slide 26 of 20 Detecting Radiation Scintillation Counter a.A scintillation counter uses a phosphor- coated surface to detect radiation. 25.4

27. © Copyright Pearson Prentice Hall Slide 27 of 20 Detecting Radiation Film Badge a.A film badge consists of several layers of photographic film covered with black lightproof paper, all encased in a plastic or metal holder. 25.4

28. © Copyright Pearson Prentice Hall Slide 28 of 20 Using Radiation How are radioisotopes used in medicine? 25.4

29. © Copyright Pearson Prentice Hall Slide 29 of 20 Using Radiation a.Neutron activation analysis is a procedure used to detect trace amounts of elements in samples. b.Neutron activation analysis is used by museums to detect art forgeries, and by crime laboratories to analyze gunpowder residues. 25.4

30. © Copyright Pearson Prentice Hall Slide 30 of 20 Using Radiation Radioisotopes can be used to diagnose medical problems and, in some cases, to treat diseases. 25.4

31. © Copyright Pearson Prentice Hall Slide 31 of 20 Using Radiation a.This scanned image of a thyroid gland shows where radioactive iodine-131 has been absorbed. 25.4

32. © Copyright Pearson Prentice Hall Slide 32 of 20 25.4 Section Quiz. 25.4.

33. © Copyright Pearson Prentice Hall Slide 33 of 20 25.4 Section Quiz. 1. Ionizing radiation can remove _______ from atoms. a.protons b.neutrons c.positrons d.electrons.

34. © Copyright Pearson Prentice Hall Slide 34 of 20 25.4 Section Quiz. 2.Which of the following is NOT a device used to detect radiation? a.geiger counter b.scintillation counter c.film badge d.radioisotope

35. © Copyright Pearson Prentice Hall Slide 35 of 20 25.4 Section Quiz. 3.Choose the correct words for the space. When a tumor is treated by radiation, more cancer cells than normal cells are killed because cancer cells ____________ than normal cells. a.are more susceptible to damage because they grow faster b.absorb more radiation because they are larger c.grow slower d.are smaller

36. © Copyright Pearson Prentice Hall Slide 36 of 20 25.4 Section Quiz. 4.How do scientists detect thyroid problems? a.with teletherapy b.by neutron activation analysis c.using an iodine-131 tracer d.using a radioisotope sealed in a gold tube

37. © Copyright Pearson Prentice Hall Slide 37 of 20 Concept Map Concept Map 25. Solve the Concept Map with the help of an interactive guided tutorial.

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