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Chapter 22 notes.

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Presentation on theme: "Chapter 22 notes."— Presentation transcript:

1 Chapter 22 notes

2 Types of nuclear reactions
Fission- splitting of nucleus- nuclear waste Fusion- nuclei can fuse together-no nuclear waste, but need 100 million degrees C to make reaction happen

3 Nuclear vs. Chemical reactions
Part of atom involved? Valence e- Protons and neutrons How reaction is started? Atoms in close proximity with high temp, pressure, catalysts, or concentrations of reactants High temperature or bombard with high-speed particles Outcome of rxn Ionic or covalent bonds # protons or neutrons changes Amt of energy released or absorbed Small Huge Examples Digestion, making medicines, cleaning products Nuclear energy, X-rays, cancer treatment, the sun

4 Forces in nucleus Strong nuclear forces overcomes repelling force of protons to keep nucleus together This force attracts every proton and neutron to each other (stronger than electromagnetic repelling force) To keep nucleus together in heavier atoms, need more neutrons than protons to overcome repelling force However past 83 p= strong nuclear force is not enough to keep atom together- unstable

5 Radioactivity Nucleus emits particles or energy
Ex- U-238 decays eventually to Pb-206 (5-billion year process) 3 types of radioactive decay Alpha- helium atom released from unstable nucleus (2p and 2n) Beta- neutron splits into a proton and electron Gamma- release of high energy, radiation from nucleus (shorter wavelength than X-rays)

6 Nuclear power Sun power is nuclear power (heat generated from fusion reactions) Nuclear reactors- use fission to produce steam to run turbines that generate electricity

7 Nuclear waste Whereas coal and fossil fuel burning contributes to global warming, nuclear reactors produce nuclear waste Waste is decaying nuclear atoms which give off radiation as they decay ½ time it takes a sample of a radioactive element to decay halfway Most radioactive elements have long ½ lives Nuclear reactors- use uranium- long ½ life

8 Nuclear Waste/reactors continued
How is the waste stored? Controversial issue! Right now stored in containers meant to last 100years Proposal is to store in Yucca Mtn, Nevada US- 20% energy from nuclear fission- France 75%- Sweden and Belgium 50% or more

9 Nuclear reactions in science
Use radioactive isotopes for medical tests Use radioactive isotopes to trace underground water supplies Nuclear reactions used to sterilize packaged foods Can predict age of fossils using radioactive isotopes Marie Curie- what were her contributions

10 Protection against radiation
Alpha particles- blocked by a sheet of paper Beta particles- clothing or wood Gamma- most dangerous need lead or concrete to block these


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