Name: Date: Text: Chapter 7, pages 312-325 Part A: Nuclear Reactions Overview -What is the difference between nuclear fission and nuclear fusion? Fission: Splitting of nuclei into two smaller nuclei; subatomic particles and energy. Fusion: Joining two low mass nuclei together to make a more massive nucleus. Part B: Nuclear Fission -Why do you think large, heavy nuclei might split apart? -Protons have the same charge and push away from each other. Science 10: 7.3 Nuclear Reactions -Allows the nuclei to reach a more stable arrangement. -Fission releases energy and neutrons. -What are some of the positives and negatives of Nuclear Fission? -Positive: Can replace the burning of fossil fuels in the production of energy (electricity). -Negative: Radio-active bi-products may need to be stored for 100s of 1000s of years, could be used for weapons Science 10: 7.3 Nuclear Reactions Page 1
Part C: Nuclear Reactions vs. Chemical Reactions -Examine the chemical reaction above. What are some general principles you can draw from it? -Conservation of Mass: Mass of the reactants = mass of the products. -Energy changes are small. -Reactant elements don t have changes to their nuclei. Products are the result of electrons reconfiguring the way atoms/ions are connected to each other. -How are nuclear reactions different from normal chemical reactions? -Changes are made to the reactant element s nuclei. Protons, neutrons, electrons and/or gamma rays can be lost or gained. -Small changes in mass result in huge changes in energy. Science 10: 7.3 Nuclear Reactions Page 2
Part C: Nuclear Equations for Induced Nuclear Reactions -What three types of radiation can potentially be released by natural radioactive decay? Alpha, beta and gamma radiation -Scientists can actually cause the radioactive decay of a nuclear by making it unstable. What is different about the reaction below from the natural radioactive decay we explored in 7.1? -Alpha particle is a reactant and not a product. Scientists can also introduce beta and gamma rays to the same effect. -The induced nuclear reaction can be written in two ways: -There are a couple of rules for writing nuclear equations: 1. The sum of the mass numbers on each side of the equation stays the same. 2. The sum of the charges on each side of the equation stays the same. *Complete Reading Check on page 315. Science 10: 7.3 Nuclear Reactions Page 3
Part D: Nuclear Fission of Uranium-235 -Examine the diagram below. Why do you think that it is easier for a neutron to be crashed into Uranium- 235 than an alpha particle into Nitrogen-14 (as depicted on the previous page)? -Alpha particle contains protons = strong repulsion from protons in Nitrogen-14 nucleus -A lot less energy is needed to add a neutron to U-235. -Why does only the mass number of uranium change and not the atomic number? -Only one neutron is added = element is still Uranium, but an isotope of. -Are both sides of the equation equal? -Yes, equal # p and n. -The nuclear fission of U-235 the reaction that occurs inside of nuclear power plants and nuclear weapons. *Complete the Practice Problems on page 317. Science 10: 7.3 Nuclear Reactions Page 4
Part E: Chain Reactions -What do you think happens to the three neutrons produced by this decay of U-236? -Chain reaction: One fission reaction triggers another. -Chain reactions can quickly get out of control, but this danger is managed in nuclear reactors by using materials that absorb neutrons. -Canada s CANDU reactors are amongst the safest in the world and produce energy by the nuclear fission of U-235. -Used U-235 rods can be hazardous to get rid of as they continue to be radioactive for twenty half-lives (thousands of years). Some rods can be re-used, but others must be stored sealed inside concrete or metal containers underground. Part F: Nuclear Fusion -Examine the diagram right. What is nuclear fusion? -Two Hydrogen nuclei join to produce a Helium nucleus and huge amounts of energy. -Nuclear fusion occurs in stars, like our Sun. Why do you think scientists have not been able to successfully recreate this reaction? -Can t replicate high temperature and pressures needed. -High temperature = no container could hold the reaction. *Complete Check Your Understanding 1-11 on page 325. Science 10: 7.3 Nuclear Reactions Page 5
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