21.6: Energy Changes in Nuclear Reactions

1. 21.6: Energy Changes in Nuclear Reactions Courtney Wong & Lauren Hebel

2. Energy Associated with Nuclear Reactions • Energy and mass of nuclear reactions are related in Einstein's famous equation • E=mc2 • E=energy • M=mass • C= speed of light (3.00 x 108) • Equation states that mass and energy are proportional • If a system loses mass, it loses energy • Vice -versa

3. Mass change, ∆m • Mass changes and associated energy changes are much greater in nuclear reactions when compared to chemical reactions • ∆m=(total mass of products) – (total mass of reactants) • -∆m= exothermic = spontaneous nuclear reaction

4. Example ∆m Problem Reaction: • 22688Ra --> 22286Rn + 42He • (mass of p) - (mass of r) • ∆m = Mass of one mole of 42He + mass of one mole of 22286Rn – mass of one mole of 22688Ra • Δm = 4.0015 g + 221.9703 g - 225.9771 g • Δm = -0.0053 g

5. Using ∆m In Einstein’s Equation • Rearranged as ∆E=c2∆m • To obtain ∆E in joules, ∆m must be converted to Kg when used in the equation • Example: Continued • ∆m = -0.0053 g • ∆E = (2.9979 x 108)2 (-0.0053) (1kg/1000g) • ∆E=-4.8x1011

6. Nuclear Binding Energies • 1930’s: scientists discovered that mass of individual parts of the nucleus always weighs more that the nucleus itself • Ex: • Helium-4 nucleus has a mass of 4.00150 amu Mass of two protons = 2(1.00728 amu) = 2.01456 amu Mass of two neutrons= 2(1.00728 amu) = 2.01456 amu Total Mass = 4.03188 amu

7. 1g 6.022 x 1023 amu 1kg 1000g Nuclear Binding Energy • Ex: (continued) Mass of two protons and two neutrons = 4.03188 amu Mass of 42He nucleus = 4.00150 amu Mass Difference (∆m) = 0.03038 amu • Mass Defect: the mass difference between a nucleus and it individual nucleons • Increase in mass = increase in energy Energy + 42He 211p + 210n so ∆E=c2∆m = (2.9979 x 108 m/s)2 (0.03038 amu) ( ) ( ) = 4.534 x 10-12 J

8. Nuclear Binding Energy • The energy required to break apart a nucleus into its individual nucleons • The larger the binding energy the more stable the nucleus is towards decomposition

9. Nuclear Binding Energy • Binding energy per nucleon increases in magnitude as mass number increases, reaching ~1.4 x 10-12 J (mass number of nuclei close to iron-56) • Then it decreases to ~1.2 x 10-12 J for a very heavy nuclei

10. Trend: nuclei of intermediate mass numbers are more tightly bound and more stable than those with either smaller or larger mass numbers 5626Fe 23892U 42He

11. Nuclear Binding Energy • Trend shows that: • Heavy nuclei gain stability and split into two mid-sized nuclei • Known as FISSION • Used to generate energy in nuclear power plants • Greater amounts of energy are released if very light are fused together to form a more massive nuclei • Known as FUSION • is an essential energy-producing process in the Sun

12. Outside Sources • http://chemistry.about.com/od/workedchemistryproblems/a/nukerxns.htm • http://wps.pearsoncustom.com/pcp_brown_chemistry_10/34/8909/2280844.cw/index.html

13. Biological Effects of Radiation Susanna Trost Kelsey Mariner

14. Natural and artificial sources Sun gives off infrared, ultraviolet, & visible radiation Television and radio stations give off radio waves Microwaves ovens give off microwaves Medical procedures can give off X-rays Natural materials like soil can have radio activity Everyday Life

15. Excitation is when excited electrons are moved to a higher energy state or the motion of molecules is increased as a result of absorbed radiation Ionization is when an electron is removed from a molecule or atom by radiation Ionizing radiation: radiation that causes ionization, can ionize water Non-ionizing radiation: radiation that does not cause ionization and has a lower energy Matter Absorbing Radiation

16. Free Radical: A substance with one or more unpaired electrons OH molecule is a highly reactive and unstable free radical Free radicals attack surrounding biomolecules which produces new free radicals One free radical can cause many chemical reactions disrupting normal cell operations H2O+ + H2O H3O+ + OH

17. Based on energy and activity of radiation, location of source, and length of exposure Gamma rays and X-rays can penetrate human tissue The skin stops alpha rays If within the body, they can transfer energy to surrounding tissues causing damage Beta rays penetrate only 1 cm into the skin Tissues that rapidly reproduce show the most damage Examples: Lymph nodes, bone marrow, and blood forming tissues Prolong exposure to radiation may lead to cancer Damage to a cells growth-regulation mechanism causes a cell to rapidly and uncontrollably reproduce Leukemia is most associated with radiation (excessive growth of white blood cells) Damaging Radiation

18. Gray and Rad are units to measure radiation exposure Gray (Gy): the SI unit of absorbed dose One joule per kilogram of tissue Rad (radiation absorbed dose): 1 x 10-2 joule of energy per kilogram of tissue 1 Gy = 100 rad Rad is the most common Radiation Doses

19. Different types of radiation harm biological materials differently RBE is a multiplication factor that measures the relative biological damage caused by radiation Multiplied by the radiation dose to correct the differences in radiation damage changes with total dose, dose rate and the type of tissue affect About 1 for beta and gamma radiation About 10 for alpha radiation Rem (roentgen equivalent for man): unit for effective dosage, more commonly used Sievert (Sv) is the SI unit for effective dosage 1 Sv = 100 rem Relative Biological Effectiveness # of rems = (# of rads)(RBE) (gray)(RBE) = Sv

20. Radioactive noble gas Radon-222 is caused from nuclear disintegration series of Uranium-238 Created in soil and rock decays as uranium Accounts for large percentage of our exposure to radiation Does not chemically react as it escapes from the ground Because it is extremely unreactive Has a very short half life Combined with its high RBE, radon is a probable cause of lung cancer when inhaled Radon-222

21. High-energy radiation is used to damage the DNA of cancer cells, which kills the cells Normal cells can also be damaged, so treatment is done very carefully Cancer cells more likely to be damaged because rapidly reproducing cells are very vulnerable to radiation damage Radiation can come from a machine or radioactive material can be injected into the bloodstream or placed directly in the body near the tumor cells Gamma rays, x-rays and charged particles can be used Radiation Therapy

22. http://www.google.com/imgres?q=wave http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/bio-effects-radiation.html http://www.cancer.gov/cancertopics/factsheet/Therapy/radiation Chemistry The Central Science Textbook Sources

23. 2.1 Radioactivity By: Margo Fox

24. Review • Nucleons- both protons and neutron • All atoms: • Same # of protons (atomic #) • Can have different # of neutrons • Mass number- total # of nucleons in nucleus • Same atomic # but different mass number- isotopes

25. Isotopes 235 92 • Uranium-235 or U • Different natural abundances • Different stabilities • Nuclide- nucleus with specified # of protons and neutrons • Radionuclides- radioactive nuclei • Radioisotopes- atoms containing those nuclei

26. Nuclear Equations • Radionuclides- unstable, spontaneously emit particles and electromagnetic radiation • Emit radiation to become more stable • Emitted radiation is carrier of the excess energy

27. Nuclear Equations Th U He • Ex: Uranium-238 and helium-4 • Helium-4 particles are known as alpha particles • Alpha radiation- stream of alpha particles • 238 234 4 92 90 2 • radioactive decay and alpha decay • 238 = 234 + 4 • 92 = 90 + 2 • Must be balanced

28. Types of Radioactive Decay 4 2

29. Beta Radiation e or β n p + e • Beta particles- high speed electrons emitted by an unstable nucleus • 0 0 -1 -1 • 1 1 0 0 1 -1

30. Gamma Radiation (Gamma Rays) • High-energy photons (electromagnetic radiation of very short wavelength) • Does not change atomic # or mass # • Represents the energy lost when remaining nucleons reorganize to be more stable • Generally not shown when writing equations

31. Positron Emission • Same mass as an electron, but opposite charge • Converts proton to neutron and decreases atomic number by 1

32. Electron Capture • The capture by the nucleus of an electron from the electron cloud surrounding the nucleus • Shown on reactant side because the electron is consumed not formed in the process • Converts proton to neutron

33. Further Research • Positron Emission Tomography Scan- imaging test to help reveal how tissues and organs are functioning • Inject, swallow, or inhale radioactive material • Accumulates in areas with higher levels of chemical activity (areas of disease) • Gamma Knife Therapy • treatment using gamma rays, a type of high-energy radiation that can be tightly focused on small tumors or other lesions in the head or neck, so very little normal tissue receives radiation

35. What Type of Radiation 81 36 81 37 11 6 11 5 0 1 0 -1

36. Bibliography • http://www.cancer.gov/dictionary?cdrid=46396 • http://www.mayoclinic.com/health/pet-scan/MY00238

37. Detection of Radioactivity By AStormy Hickey and The Austin McCadden

38. Discovery of Radiation • Was discovered by Henri Becquerel • Observed effect of radiation on photographic plates • Received 1903 Nobel Prize for his works • SI unit for expressing radiation activity was named becquerel (Bq)

39. Effects of radiation • Radiation affects photographic film the same way it does X-rays • Increased radiation darkens negative are on film • Used by people who work with radiation to see extent of exposure

40. Ways of Detection • Geiger counter • detects and measures radioactivity • Use is based on the ionization of matter caused by radiation • Ions and electrons permit conduction of electrical current

41. Geiger Counter • Consists of a metal tube filled with gas • Tube has a “window” that can be infiltrated by alpha, beta, or gamma rays • Wire in tube connected to a source of direct current • Current flows between the wire and tube when ions are produced by entering radiation • Records pulses that indicate presence of radiation

42. Other Indicators of Radiation • Phosphors- • excited by radiation give off light when electrons return to lower-energy states • Ex: Zinc sulfide is excited by alpha particles

43. Scintillation Counter • Measures radiation based on tiny flashes of light • Flashes of light produced when radiation strikes a phosphor that’s suitable • Flashes are magnified electronically and counted to measure radiation

44. Radioisotopes • Radioisotopes can be detected readily, used to follow element through chemical reactions • Possible because all isotopes of an element have essentially identical chemical properties

45. Radioisotopes Continued • When small amounts of radioisotopes are mixed with the naturally occurring stable isotopes, all isotopes go through same reaction together • Element can be tracked in reaction or process by tracing radioactivity • Because Radioisotopes trace paths of element they are called Radiotracers

46. Additional Research Gold Leaf Electroscope • When electroscope is charged, the gold leaf sticks out, because charges on gold repel charges on metal stalk • Radiation ionizes air, and conducts electricity • The charge leaks away from electroscope, discharging it and the gold leaf falls.

47. Additional Research Cont. • Personal radiation detectors can be purchased at a relatively low price PDS-100G Sensitive Survey Meter

48. Questions How did Becquerel discover radiation? How can Radioisotopes be used to track the path of an element?

49. Sources http://www.darvill.clara.net/nucrad/detect.htm http://www.mirion-hp.com/portableinstruments.asp?_kk=detection%20of%20radioactivity&_kt=43082093-d735-446c-87b0-366f3477100f&gclid=CMCRpffE4q4CFYuK4Aod7G9bZw

50. 21.8 Nuclear Fusion Stephanie Cho Abigail Wang