CHEM 1120 1st Edition Lecture 11Outline of Last Lecture 1. Nuclear stability continued2. Nuclear transmutation3. Rates of radioactive decay4. Detection of radioactivity5. Applications of radioactivity Outline of Current Lecture Current Lecture21.6 Energy Changes in Nuclear Reactions- Radioactive decayo Nucleus emits one or a few small particles or photons to become a slightly lighternucleus- Nuclear Fission/Fusion (two other processes that cause much greater changes) They both release enormous quantities of energyo Fission Heavy nucleus splits into two much lighter nuclei emitting sever small particles at the same timeo Fusion Two lighter nuclei combine to form a heavier one- Mass defect o Mass and energy are interconvertible – total quantity of mass and energy is constanto Einstein equation  E = mc^2 E = energy M= mass C = speed of lightThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Nuclear reaction are accompanied by a loss or gain of masso mass is conserved in chemical reactionso The much larger mass change for nuclear processes is related to the enormous energy required to bind the nucleus together or break it apart o **see slide 52 for reaction energy and mass change exercise- Nuclear binding enegieso Nuclear masses are always less than the sum of the masses of their nucleons, i.e. protons and neutronso Mass defect = mass difference between nucleus and its individual nucleons- Nuclear binding energyo Energy required to separate a nucleus into its individual nucleons o Nucleus + nuclear binding energy  nucleonso Nuclear binding energy = mass defect x c^2o Slide 53-54 for nuclear binding energy exercise- Nuclear binding energy in Mevo Joules is to large of a unit to express the binding energy of a single nucleus o Electron volt Energy an electron acquires when it moves through a potential diffence of1 volt - 1eV = 1.602^-19 J- Mega-electron volts (MeV) = 10^6 eV = 1.602x10^-13o Useful conversion factor 1 amu = 931.5x10^6 eV = 931.5 MeVo Slides 54-56 for MeV exercise(s)21.7 Nuclear Power: Fission- Most beneficial application is production of large amount of energy- Must utilize this energy source safely and efficiently- Subcritical and supercritical fissiono Critical mass Mass required to achieve a chain reactiono Supercritical mass Mass in excess of the critical mass- Controlled vs. uncontrolled fissiono Controlled fission – nuclear energy reactors Electric power can be produced more cleanly than coal A nuclear power plant generates heat to produce steam, which turns a turbine attached to an electric generator  s Safe disposal of nuclear waste is a serious problemo Uncontrolled chain reaction can create a powerful explosive Manhattan project (1941) - Scientific effort to develop a bomb based on nuclear fission- Lead to A-bomb- Nuclear Power Planto In nuclear reactors, heat generated by the reaction us used to produce steam that turns a turbine connected to a generator21.8 Nuclear Power: Fusion- Energy from sun results from series of nuclear fusion reactions- Very appealing energy source- Fuels are virtually limitless- For most part, waste is not radioactive- High temps are required (around 100,000,000 K)- At these high temps, matter exists as plasma: neutral mixture of positive nuclei and electrons. Must be confined in a manner that does not destroy its container- Enclose plasma within a magnetic field: tokamak-magnetic bottle (see slide 68 for picture)- Smoke detectorso See slide 71- Energy of transmuting collisionso Neutrons require minimal kinetic energy in order to collide with nucleus o A proton required very high kinetic energy in order to overcome repulsion from the nucleuso Particles with such kinetic energy produced in particle accelerators: linear accelerators and cyclotrons- Nuclear isotope datingo Carbon 14 half life of 5730 yearso Used to date objects up to 36,000 years