CHEM 105 1nd Edition CHAPTER 5 Lecture 12Outline of Last Lecture • Cont. Balancing Redox Reactions • Balance acid Outline of Current Lecture • Exothermic Reaction• Endothermic Reaction • Heat and Work• Boiling water Current Lecture-There are many concepts and definitions in the first two sections of chapter 5. Read themcarefully.system: the substances currently under examination. In chemistry, it is the reactants andproducts of a chemical reaction.surroundings: The materials in immediate thermal contact with the system. Usually the solvent and the container.An endothermic system (reaction) absorbs heat energy.An exothermic system (reaction) releases heat energyAre these processes endothermic or exothermic?• boiling water• molten iron solidifying (freezing)-The internal energy (E) is the sum of the kinetic energy (motion of the atoms and molecules) and the potential energy (position of the atoms and molecules with respect to each other.)ÄE = E(Final)-E(initial) usually weitten E(f)-E(I)For a chemical reaction: ÄE = Eproducts -Ereactants-How is the energy transferred?• as Heat (q)-energy transferred as a result of a temperature difference [from hot to cold]• as Work (w)-energy transferred when a force moves an objectÄE = q + w• Heat added to the system is defined as positive q• Work done on the system is defined as positive w-Energy gained by the system comes from the surroundings. Energy lost by the system goes to the surroundings.Q: A chemical reaction absorbs 3.21 kJ of heat and does 1.87 kJ of work on the surroundings. What is ÄE?A: ÄE=
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