7.3 nuclear reactions: nuclear reactions are different than chemical reactionsnuclear reactions are...

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  • 7.3 Nuclear Reactions:Nuclear reactions are different than chemical reactions

    Chemical ReactionsMass is conserved (doesnt change)Small energy changesNo changes in the nucleiNuclear ReactionsSmall changes in massHuge energy changesprotons, neutrons, electrons and gamma rays can be lost or gained

  • Induced Nuclear ReactionsScientists can also force ( = induce) nuclear reactions by smashing nuclei with alpha, beta and gamma radiation to make the nuclei unstableor

  • Symbols to Remember:

  • Nuclear ReactionsTwo types:Fission = the splitting of nucleiFusion = the joining of nuclei (they fuse together)Both reactions involve extremely large amounts of energy

    Albert Einsteins equation E = mc2 illustrates the energy found in even small amounts of matter

  • 1. Nuclear Fission:Nuclear fission is the splitting of one heavy nucleus into two or more smaller nuclei, as well as some sub-atomic particles and energy.A heavy nucleus is usually unstable, due to many positive protons pushing apart.When fission occurs:Energy is produced.More neutrons are given off.

  • Induced Nuclear FissionNeutrons are used to make nuclei unstableIt is much easier to crash a neutral neutron than a positive proton into a nucleus to release energy.

  • Induced Nuclear Fission of Uranium-235is the origin of nuclear power and nuclear bombs.A neutron, , crashes into an atom of stable uranium-235 to create unstable uranium-236, which then decays.After several steps, atoms of krypton and barium are formed, along with the release of 3 neutrons and huge quantities of energy.

  • Chain Reactions:The neutrons released in the induced reaction can then trigger more reactions on other uranium-235 atomscausing a CHAIN REACTION

  • A chain reaction can quickly get out of controlmaterials that absorb some neutrons can help to control the chain reaction.Nuclear reactors have complex systems to ensure the chain reaction stays at safe levels.An uncontrolled chain reaction can result in the release of excess energy as harmful radiationIt is on this concept that nuclear bombs are created.Nuclear meltdown occurs if the chain reactions cannot be controlled

  • Nuclear energy used to produce power comes from fissionNuclear power plants can generate large amounts of electricity.In Canada, Ontario, Quebec and New Brunswick currently use nuclear power.Canadian-made nuclear reactors are called CANDU reactors.CANDU reactors are considered safe and effective, and are soldthroughout the world.

    The Bruce Nuclear Generating Station on the shores of Lake Huron, in Ontario

  • CANDU ReactorsCANDU reactors are found in various countries around the world.Canada, South Korea, China, India, Argentina, Romania and PakistanThe reactors are known to be safe and easy to shut down in an emergency.Heat energy produced turns electricity-generating turbines.

  • Hazardous WastesHazardous wastes produced by nuclear reactions are problematic.Some waste products, like fuel rods, can be re-usedSome products are very radioactive, and must be stored away from living things.Most of this waste is buried underground, or stored in concreteIt takes 20 half-lives (thousands of years) before the material is safe.

  • Provincial Exam Question

  • 2. Nuclear Fusionjoining of two light nuclei into one heavier nucleus.In the core of the Sun, two hydrogen nuclei join under tremendous heat and pressure to form a helium nucleus.When the helium atom is formed, huge amounts of energy are released.

    The fusion of hydrogen nuclei

  • Provincial Exam Question

  • Provincial Exam Question

  • Provincial Exam QuestionWhich isotope correctly completes the following nuclear reaction?Helium-4Barium-141Strontium-90Cesium 143

  • Scientists cannot yet find a safe, and manageable method to harness the energy of nuclear fusion.cold fusion would occur at temperatures and pressures that could be controlled (but we havent figured out how to get it to happen)

    Take the Section 7.3 Quiz

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