Nuclear Physics. Physical Phase Change Material still has the same chemical properties. Types of Changes

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1 Nuclear Physics Project 2013 Nuclear Physics Chapters 39 and 40 Phase One Prepare a Position Poster In groups of 2 or 3, choose a topic from Chapter 39/40 that has economic, political, environmental or ethical issues associated with it. Prepare a strong statement of your position on the issue. Develop 5 supporting statements from the information and document the source of each fact. Submit your poster in Google Docs (give me the link) The statements will be posted for viewing on the physics web site. Phase Two Feedback Each student (not group work) will comment on 5 of the posters in a meaningful way. Comments on the strength of the statement, questions about the source of data, additional support or rebuttal would all be appropriate. Phase Three Response Each group will select one or more comments and respond to it. Types of Changes Physical Phase Change Material still has the same chemical properties. Physical Chemical Nuclear Chemical Double Replacement New materials with new chemical properties are formed. Nuclear Transmutation One element is changed into another. Unaffected by harsh chemical conditions. 1

2 Models of the Atoms Dalton Atoms cannot be subdivided Thompson s Atomic Model 1900 They still did not know about the nucleus not even that it existed. Henri Becquerel Discovers Radiation Curie s Make Radium Available for Study 1902 Image of Becquerel's photographic plate which has been fogged by exposure to radiation from uranium salts. The shadow of a metal Maltese Cross placed between the plate and the uranium salts is clearly visible Marie and Pierre Curie isolate radioactive radium salts from pitchblende in Paris 2

3 Rutherford s Gold Foil Rutherford s Lab Exposure to radiation causes illness. During World War One Curie helped to equip ambulances with x-ray equipment, which she herself drove to the front lines. The International Red Cross made her head of its radiological service and she held training courses for medical orderlies and doctors in the new techniques. She died on 4 July 1934 from leukemia, caused by exposure to high-energy radiation from her research. Radium Girls 1920 s The U.S. Radium Corporation hired about 70 women to perform various tasks including the handling of radium, which glows in the dark. The owners and their scientists familiar with the effects of radium carefully avoided any exposure to it themselves. The going rate, for painting 250 dials a day, was about a penny and a half per dial. Brushes would lose shape after a few strokes, so the U.S. Radium supervisors encouraged their workers to point the brushes with their lips. Radium Girls Bad, Bad, U.S. Radium Company The Radium Girls painted their nails, teeth and faces with the deadly paint produced at the factory, sometimes to surprise their friends when the lights went out. Many of the women later began to suffer from anemia, bone fractures and necrosis of the jaw, a condition now known as radium jaw. At the urging of the companies, worker deaths were attributed by medical professionals to other causes; syphilis was often cited in attempts to smear the reputations of the women. 3

4 The Lawsuit Nuclear Radiation 3 types Plant worker Grace Fryer decided to sue, but it took two years for her to find a lawyer willing to take on U.S. Radium. The litigation and media sensation surrounding the case established legal precedents and triggered the enactment of regulations governing labor safety standards. The right of individual workers to sue for damages from corporations due to labor abuse was established as a result of the Radium Girls case. Alpha: 2P2N Mass = 4 Charge = +2 Beta: electron Mass = 0 Charge = -1 Gamma: photon Mass = 0 Charge = 0 Types of Radiation Penetrating Power This is why radium, which emits alpha and beta particles was safe for the person who wore the watch. The particles did make it out through the glass and metal of the watch. Only eating or breathing it was dangerous. Describing the Nucleus Particles in the Nucleus Protons Mass = 1 u Charge = +1 Neutrons Mass = 1 u Charge = 0 Together they are referred to as Nucleons 4

5 The Strong Force How can all those + charges stay together in the nucleus? Don t they repel each other? Protons which would otherwise strongly repel at close distances are held in place by an extremely strong, but extremely short range force called the strong force. The strong force between two protons is about the same as the strong force between two neutrons, or a proton and a neutron. The Strong Force Beyond about one fermi the strong force declines extremely rapidly. As more protons are added to the nucleus, more neutrons are needed to bind the protons together, but the larger the nucleus becomes, the farther apart are the protons and the less effective is the strong force. Extra Neutrons Add Stability they increase the strong nuclear attraction force but don t increase the electrical repulsion force. Large Nuclei what happens to them? Isotopes - Same Protons Different Neutrons 5

6 Half-Life The pile doesn t get smaller. The unstable nuclei don t disappear, they change into another type of nucleus. The pile becomes less radioactive, not smaller (unless the new element is a gas!) 39-2 Half Life The instructions talk about students tossing a coin. We will increase the number of events by using M&Ms. The blank M&Ms are the ones that decay. Record your results on a piece of paper and transfer then to the board. Graph the COLLECTIVE data, not just yours. Worksheets 39-1 and 39-2 are due tomorrow. 6