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Nuclear Reactions:. FISSION & FUSION. Introduction. Nuclear reactions deal with interactions between the nuclei of atoms Both fission and fusion processes deal with matter and energy. Matter and Energy. Previous studies have taught us that “matter and energy cannot be created nor destroyed”
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Nuclear Reactions: FISSION & FUSION
Introduction • Nuclear reactions deal with interactions between the nuclei of atoms • Both fission and fusion processes deal with matter and energy
Matter and Energy • Previous studies have taught us that “matter and energy cannot be created nor destroyed” • We now need to understand that Matter and Energy are two forms of the same thing
E = mc2 • Remember that matter can be changed into Energy • This tells us that a small amount of mass can be converted into a very largeamount of energy because the speed of light (c) is an extremely large number Light Speed Energy Mass
Fission • Fission may be defined as the process of splitting an atomic nucleus into fission fragments • The fission fragments are generally in the form of smaller atomic nuclei and neutrons • Large amounts of energy are produced by the fission process
Fission • Fissile nuclei are generally atoms with more neutrons than protons • The nuclei of such heavy atoms are struck by neutrons initiating the fission process • Fission occurs when the strong nuclear force is disrupted by an incoming projectile (in this case a neutron) • When the strong nuclear force is disrupted electrostatic repulsion splits the nuclei
Fission • A classic example of a fission reaction is that of U-235: U-235 + 1 Neutron 3 Neutrons + Kr-91 + Ba-142 + Energy • In this example, a stray neutron strikes an atom of U-235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.
Fission • Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity.
Fusion • Fusion is a nuclear reaction whereby two light atomic nuclei fuse or combine to form a single larger nuclei which is lighter than the sum of the two that fuse. • The lost mass is converted to energy. (E = mc2 ) • For fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together
Fusion • Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars • The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions • The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy
Energy Comparison • Because of the large binding energies involved in a nucleus, both fission and fusion involve energy changes of more than a million times larger than those energy changes associated with chemical reactions.
Review • Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc2) • Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei • Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus
Quiz • Which nuclear process produces large amounts of energy? A. Fission B. Fusion C. Both fission & fusion D. Neither fission nor fusion
Quiz • Fission is the process that _________ atomic nuclei. A. Combines B. Burns up C. Stores D. Splits
Quiz • Mass may be converted into energy. A. True B. False
Quiz • The fission process requires heavy atomic nuclei. A. True B. False
Quiz • Name a nuclear reaction that occurs within the sun:
Quiz • Fission is a natural process that occurs on the planet Earth. A. True B. False
Quiz • Explain this equation: E = mc2
