Purely particles - nothingnerdy IGCSE Physics
- 1. presents a production Purely Particles
- 2. Pre-nuclear model JJ Thomson proposed the ‘plum pudding model’. Image: mhhe.com (This model is not correct) In the model, the mass and charges in the atom are spread uniformly throughout the atom.
- 3. Geiger and Marsden In 1911, they fired alpha particles at gold foil. Image: mhhe.com Gold foil Alpha emitter Round screen The theories of the time predicted that the particles would easily pass through the thin foil since the gold was not dense enough to stop them.
- 4. Unexpected result Some alphas bounced right back! Most alphas passed straight through as predicted. Some were slightly deflected. But one in 8 000 was bounced right back. Rutherford said: “It was quite the most incredible event that has ever happened to me in my life ... It was then that I had the idea of an atom with a minute massive centre, carrying a charge.” Image: PHET
- 5. Rutherford’s model He discovered the nucleus The nucleus of the atom is 20 000 times smaller than the atom itself but contains nearly all of its mass and the positive charge. Empty Nucleus space The alpha particles are repelled by the nucleus (both positive charges). A larger nucleus repels more strongly. The faster the alpha particles, the less they are deflected.
- 6. Nuclearsplitting an unstable nucleus. Huge amounts of energy from fission Can you balance the 1n neutron nuclear equation? Solution over page neutron fissions U-235 into 2 smaller daughter nuclei gamma The products are: 141Ba ★two nuclei eg krypton-92 and 92Kr barium-141 both with a lot of KE ★three neutrons with KE ★gamma rays at the speed of light 3 1n Image: PHET
- 7. Chainproduce energy from fission How to continually reaction The fuel is enriched U-235, since U-238 does not fission. The fission reaction produces fast neutrons. When these are slowed down, they can cause new fission which produces more fast neutrons ... Scientists realised that if at least one neutron caused new fission, there would be a chain reaction. U 235 92 1 141 92 1 + n 0 → Ba 56 + Kr 36 + 3n 0 plus loads and loads of energy Image: PHET
- 8. Nuclear fission reactor The KE of the products makes the core extremely hot. This heat energy is transferred to the exchanger; steam turns the turbine and electricity is generated. Image: Adrian Watt, Absorb Physics
- 9. Parts of a nuclear reactor PART OF FUNCTION POSSIBLE REACTOR OF THE PART MATERIALS Fuel rods Chain reaction Enriched uranium oxide in zirconium alloy Slow down fast Graphite or Moderator neutrons heavy water Absorb excess Boron or cadmium Control rods neutrons Water or carbon dioxide Coolant Transfer heat energy or liquid sodium Thick lead, steel Containment Radiation protection or concrete
- 10. Nuclear accident 2011? What happened at Fukushima, Japan in March When the earthquake struck, the A were Fill in the blanks chain pushed into the B to absorb neutrons and reaction stop the C reaction in the D. But the control earthquake had damaged the cooling rods system, so super-hot E built up and reacted core with the F round the fuel rods to produce fission hydrogen which exploded. The hot core fuel rods broke through the G containment vessel neutrons and released H materials to the radioactive surroundings. To stop the reaction, acid containing boron was added to absorb I and steam stop the J. steel zirconium
- 11. INTERESTING, BUT NOT FOR THE IGCSE The interior of nuclear reactors glows blue because of Cherenkov radiation which is caused by electrons travelling in matter at speeds faster than light can travel in that medium. Image: wikipedia
- 12. a production MUCH MORE AT http://nothingnerdy.wikispaces.com http://nothingnerdy.wikispaces.com/IGCSE+PARTICLES