Chapter 14 - Chapter 14 Heat Work Energy Enthalpy 1 The...

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Chapter 14 Heat, Work, Energy, Enthalpy 1 The Nature of Energy 2 Enthalpy 3 Thermodynamics of Ideal Gases 4 Calorimetry 5 Hess's Law 6 Standard Enthalpies of Formation 7 Present Sources of Energy (skip) 8 New Energy Sources (skip)
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James Prescott Joule (1818-1889) Highlights English physicist and !!brewer!! Studied the nature of heat, and discovered its relationship to mechanical work Challenged the "caloric theory”l that heat cannot be created nor destroyed. Led to the theory of conservation of energy, which led to the development of the first law of thermodynamics Worked with Lord Kelvin to develop the absolute scale of temperature Pupil of John Dalton (Atomic Theory) Joule effect: found the relationship between the flow of current through a resistance and the heat dissipated, now called Joule's law Moments in a Life (Death) Gravestone is inscribed with the number “772.55” the amount of work, in ft lb, he determined experimentally to be required to raise the temperature of 1 lb of water by 1° Fahrenheit. “772.55”
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Thermite Reaction Reactants → Products 2 Al (s) + Fe 2 O 3 (s) → Al 2 O 3 (s) + 2Fe (s)
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Energy Definition of Energy: Capacity to do work. The study of energy and its interconversions is called Thermodynamics. 1 St Law of Thermodynamics: Conservation of energy . Energy can be converted from one form to another but cannot be created of destroyed. The energy of the universe is constant. The energy of a closed system is constant. Heat and work are interconvertable
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Forms of Energy Chemical Energy • Potential energy ( e.g ., ΔE potential = mgΔh) • Kinetic energy ( e.g ., ΔE Kinetic = Δ (1/2mv 2 ) Electrical Energy Nuclear Energy Energy transfer Through heat Through work
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Energy Energy is a state property , which means it depends on the initial and final state, not the path between them. ΔE = E final – E initial ΔE = E products – E reactants
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What is a “State Property”?
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Thermodynamics: Systems and Surroundings A thermodynamic system is the part of the universe that is under consideration. A boundary separates the system from the rest of the universe, which is called the surroundings. A system can be anything that you wish it to be, for example a piston, and engine, a brick, a solution in a test tube, a cell, an electrical circuit, a planet, etc.
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Heat (q) and Work (w) ΔE = q + w q = Heat absorbed by the system If q > 0 , heat is absorbed If q < 0 , heat is given off w = Work done on the system Increase the energy of a system by heating it (q>0) or by doing work on it (w>0). Work w = Force x distance = (Pressure x area) x distance = pressure x ΔV = PΔV Work is Pressure-Volume work (P-V)
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Exo thermic reactions release energy to surroundings (by heating the surroundings) CH 4 ( g ) + 2O 2 ( g ) → CO 2 ( g ) +2 H 2 O ( g ) + heat In an exo thermic process, the energy stored in chemical bonds/molecular interactions is converted to thermal energy (random kinetic energy).
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Endo thermic reactions absorb energy N 2 ( g ) + O 2 ( g ) + Energy (heat) → 2 NO ( g
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This note was uploaded on 09/07/2010 for the course CHEM 1310 taught by Professor Cox during the Fall '08 term at Georgia Tech.

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Chapter 14 - Chapter 14 Heat Work Energy Enthalpy 1 The...

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