The Hindenburg Disaster 1937

1. The Hindenburg Disaster1937

2. MAJOR DISASTERS The Titanic 1912 Tacoma bridge 1940 Twin Towers 2001

3. Hiroshima and Nagasaki1945 Two atomic bombs: 6th Aug 1945 : Little Boy Hiroshima 9th Aug 1945 : Fat Man  Nagasaki

4. Form 5 Physics Nuclear Reactions Fission and Fusion GEE KUANG BENG SMK METHODIST (ACS)

5. Little Boy – Atom Bomb – Hiroshima 6 Aug 1945

6. CS 5.4 Understanding nuclear energy • You should be able to • define atomic mass unit (a.m.u) • describe and give examples of nuclear fission • describe Chain reactions • describe and give examples of nuclear fussion • relate release of nuclear energy to the equation E=mc2 • describe generation of electricity from nuclear fission PHEW!

7. Fission When atoms are bombarded with neutrons, their nuclei splits into 2 parts which are roughly equal in size. Nuclear fission in the process whereby a nucleus, with a high mass number, splits into 2 nuclei which have roughly equal smaller mass numbers. During nuclear fission, neutrons are released.

8. 235 1 U n 92 0 The Fission Process A neutron travels at high speed towards a uranium-235 nucleus.

9. 235 1 U n 92 0 The Fission Process The neutron strikes the nucleus which then captures the neutron.

10. 236 U 92 The Fission Process The nucleus changes from being uranium-235 to uranium-236 as it has captured a neutron.

11. The Fission Process The uranium-236 nucleus formed is very unstable. It transforms into an elongated shape for a short time.

12. The Fission Process The uranium-236 nucleus formed is very unstable. It transforms into an elongated shape for a short time.

13. The Fission Process The uranium-236 nucleus formed is very unstable. It transforms into an elongated shape for a short time.

14. 1 1 1 n n n 0 0 0 92 141 Ba Kr 36 56 The Fission Process It then splits into 2 fission fragments and releases neutrons.

15. 1 1 1 n n n 0 0 0 92 141 Ba Kr 36 56 The Fission Process It then splits into 2 fission fragments and releases neutrons.

16. 1 1 1 n n n 0 0 0 92 141 Ba Kr 36 56 The Fission Process It then splits into 2 fission fragments and releases neutrons.

17. 1 1 1 n n n 0 0 0 92 141 Ba Kr 36 56 The Fission Process It then splits into 2 fission fragments and releases neutrons.

18. Nuclear Fission 1n + 235U -> 91Kr + 142Ba + 31n

19. 235 235 141 96 92 138 U U Cs Kr Ba Rb 2 3 + + + + + + 92 92 55 36 37 56 1 1 1 1 n n n n 0 0 0 0 Nuclear Fission Examples

20. E c2 m Energy Released The energy released can be calculated using the equation: E = mc2 Where: E = energy released (J) m = mass difference (kg) c = speed of light in a vacuum (3 x 108 ms-1)

21. Mass-Energy Relationship Einstein’s famous equation E = mc2 A nucleus is measured to have less mass than the sum of its parts 12C has a mass exactly 12.00000 amu Six protons have mass 6 x 1.00728 amu Six neutrons have mass 6 x 1.00867 amu Parts have mass 12.09570 amu

22. Mass-Energy Relationship So, where does the mass go? It is the binding energy that is holding the nucleus together Interesting to look at the mass per nucleon as we change the atomic number (change which element we look at)

23. + + + 235 138 96 U Cs Rb 2 92 37 55 1 1 n n 0 0 Energy from Fission

24. Energy from Fission Calculate the total mass before and after fission takes place. The total mass before fission (LHS of the equation): 3.91815 x 10-25 kg 3.9014 x 10-25 + 1.6750 x 10-27 = The total mass after fission (RHS of the equation): 3.9155 x 10-25 kg 2.2895 x 10-25 + 1.5925 x 10-25 + (2 x 1.6750 x 10-27) =

25. Energy from Fission The total mass before fission = 3.91815 x 10-25 kg 3.91550 x 10-25 kg The total mass after fission = total mass before fission > total mass after fission

26. Energy from Fission mass difference, m = total mass before fission – total mass after fission m = 3.91815 x 10-25 – 3.91550 x 10-25 m = 2.65 x 10-28 kg This reduction in mass results in the release of energy.

27. + + + 235 96 138 U Cs Rb 2 92 37 55 1 1 n n 0 0 Energy from Fission Calculate the energy released from the following fission reaction: m = 2.65 x 10-28 kg E = mc2 E = 2.65 x 10-28 x (3 x 108)2 c = 3 x 108 ms-1 E = 2.385 x 10-11 J E = E

28. Energy from Fission The energy released from this fission reaction does not seem a lot. This is because it is produced from the fission of a single nucleus. Large amounts of energy are released when a large number of nuclei undergo fission reactions.

29. Energy from Fission Each uranium-235 atom has a mass of 3.9014 x 10-25 kg. The total number of atoms in 1 kg of uranium-235 can be found as follows: No. of atoms in 1 kg of uranium-235 = 1/3.9014 x 10-25 No. of atoms in 1 kg of uranium-235 = 2.56 x 1024 atoms

30. Energy from Fission If one uranium-235 atom undergoes a fission reaction and releases 2.385 x 10-11 J of energy, then the amount of energy released by 1 kg of uranium-235 can be calculated as follows: total energy = energy per fission x number of atoms total energy = 2.385 x 10-11 x 2.56 x 1024 total energy = 6.1056 x 1013 J

31. Chain Reaction

32. Nuclear fission starts a chain reaction

33. Chain Reaction The key to keeping the reaction going is that at least one of the neutrons given off, must cause another fission Controlled reaction in a nuclear reactor If two or three cause fissions, you can get a bomb! Idea of critical mass

34. Critical Mass

35. Atom Bomb

36. Nuclear Reactor

37. Figure 19.6: Diagram of a nuclear power plant.

38. 2 4 H He 1 2 Energy + + + 1 3 n H 0 1 Nuclear Fusion In nuclear fusion, two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number.

39. 2 3 H H 1 1 The Fusion Process

40. 2 3 H H 1 1 The Fusion Process

41. 2 3 H H 1 1 The Fusion Process

42. 2 3 H H 1 1 The Fusion Process

43. The Fusion Process

44. The Fusion Process

45. The Fusion Process

46. The Fusion Process

47. 4 He 2 1 n 0 The Fusion Process ENERGY

48. 4 He 2 1 n 0 The Fusion Process ENERGY

49. 4 He 2 1 n 0 The Fusion Process ENERGY

50. 4 He 2 1 n 0 The Fusion Process ENERGY