1 / 48

Do now!

Do now!. Can you read the last powerpoints that Mr Porter gave you?. ½ - life. This is the time it takes half the nuclei to decay. Number of nuclei undecayed. A graph of the count rate against time will be the same shape. time. half-life (t ½ ). Different ½ - lives.

dorian-raymond
Télécharger la présentation

Do now!

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Do now! • Can you read the last powerpoints that Mr Porter gave you?

  2. ½ - life • This is the time it takes half the nuclei to decay Number of nuclei undecayed A graph of the count rate against time will be the same shape time half-life (t½)

  3. Different ½ - lives • Different isotopes have different half-lives • The ½-life could be a few milliseconds or 5000 million years! Number of nuclei undecayed time half-life (t½)

  4. Questions! Homework Can you finish questions 1,2 and 3 that Mr Porter gave you last lesson AND do the questions on page 259 of your textbook. Due next Tuesday 24th November

  5. Do now! In pairs, can you decide which of the following energy sources is the odd one out? Biomass, tidal, solar, hydroelectric, wave, coal, oil, wind.

  6. Do now! In pairs, can you decide which of the following energy sources is the odd one out? Biomass, tidal, solar, hydroelectric, wave, coal, oil, wind.

  7. Nuclear Physics

  8. How do we know the structure of the atom?

  9. The famous Geiger-Marsden Alpha scattering experiment In 1909, Geiger and Marsden were studying how alpha particles are scattered by a thin gold foil. Thin gold foil Alpha source

  10. Geiger-Marsden As expected, most alpha particles were detected at very small scattering angles Thin gold foil Small-angle scattering Alpha particles

  11. Geiger-Marsden To their great surprise, they found that some alpha particles (1 in 20 000) had very large scattering angles Thin gold foil Small-angle scattering Alpha particles Large-angle scattering

  12. Can you QUICKLY, quietly and sensibly follow Mr Porter?

  13. Explaining Geiger and Marsdens’ results The results suggested that the positive (repulsive) charge must be concentrated at the centre of the atom. Most alpha particles do not pass close to this so pass undisturbed, only alpha particles passing very close to this small nucleus get repelled backwards (the nucleus must also be very massive for this to happen). nucleus

  14. Rutherford did the calculations! Rutherford (their supervisor) calculated theoretically that the atomic nucleus was confined to a diameter of about 10-15 metres. That’s 10 000 times smaller than the size of an atom(about 10-10 metres).

  15. Rutherford did the calculations! If the nucleus of an atom was a ping-pong ball, the atom would be the size of a football stadium (and mostly full of nothing)! Nucleus (ping-pong ball

  16. Nuclear Fission

  17. Uranium Uranium 235 has a large unstable nucleus.

  18. Capture A lone neutron hitting the nucleus can be captured by the nucleus, forming Uranium 236.

  19. Capture A lone neutron hitting the nucleus can be captured by the nucleus, forming Uranium 236.

  20. Fission The Uranium 236 is very unstable and splits into two smaller nuclei (this is called nuclear fission)

  21. Fission The Uranium 236 is very unstable and splits into two smaller nuclei (this is called nuclear fission)

  22. Free neutrons As well as the two smaller nuclei (called daughternuclei), three neutrons are released (with lots of kinetic energy)

  23. Fission These free neutrons can strike more uranium nuclei, causing them to split.

  24. Chain Reaction If there is enough uranium (critical mass) a chain reaction occurs. Huge amounts of energy are released very quickly.

  25. Chain Reaction If there is enough uranium (critical mass) a chain reaction occurs. Huge amounts of energy are released very quickly. YouTube - Mousehunt Movie part 4 (English)Related Videos

  26. Bang! This can result in a nuclear explosion!YouTube - nuclear bomb 4

  27. Controlled fission The chain reaction can be controlled using control rods and a moderator. The energy can then be used (normally to generate electricity).

  28. Moderator This slows the free neutrons down, making them easier to absorb by the uranium 235 nuclei. Graphite or water is normally used.

  29. Control rods These absorb excess neutrons,making sure that the reaction does not get out of control. Boron is normally used.

  30. Heat The moderator gets hot from the energy it absorbs from the neutrons.

  31. Heat This heat is used to heat water, to make steam, which turns a turbine, which turns a generator, which makes electricity.

  32. Nuclear Power That’s how a nuclear power station works!

  33. Let’s try some questions. Can you now read pages 260 and 261 and mind-map fission and nuclear power

  34. Let’s try some questions. Can you READ pages 264 and 265 of the book?

  35. Used as Tracers

  36. Used as Tracers

  37. Used as Tracers

  38. Killing microbes

  39. Killing microbes

  40. Thickness control

  41. Thickness control

  42. Smoke detection

  43. Checking welds

  44. Radioactive dating

  45. Summary sheet

  46. Can you answer the questions on pages 261 and 265?

More Related