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CHEMICAL THERMODYNAMICS 1 chem 16 4 slides per page

CHEMICAL THERMODYNAMICS 1 chem 16 4 slides per page -...

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1/7/2014 1 THERMODYNAMICS Study of the changes of energy that accompany chemical and physical processes. CHEMICAL THERMODYNAMICS and THERMOCHEMISTRY 3 fundamental questions. 1. Will two (or more) substances react when they are mixed under specified conditions? 2. If they do react, what energy changes are associated with their reaction? 3. To what extent does the observed reaction occur? CHEMICAL THERMODYNAMICS SYSTEMS and SURROUNDINGS Types of Systems: System Matter flow Heat Work Isolated xmarkbld xmarkbld xmarkbld Open checkbld checkbld checkbld Closed xmarkbld checkbld checkbld Thermally isolated xmarkbld xmarkbld checkbld Mechanically Isolated xmarkbld checkbld xmarkbld Energy in the system, relative to its surroundings
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1/7/2014 2 Transfer of Energy -Heat q square4 Thermal energy transferthrough conduction, convection, or radiation square4 Observedwhen substance's temperature changes square4 + if into the system square4 - if out of the system square4 Unit:joule (J) 1 J = 1 kg· m 2 /s 2 1 J = 0.2390 cal 1 cal= 4.184 J 1 Btu (British thermal unit) = 1055 J THERMAL ENERGY of a system –associated with potential and kinetic energy of that system, which makes up its temperature Transfer of energy -work w square4 Energy transfer based on changes of mechanical constraints present onthe system. Most common form of mechanical constraint is one that causes pressure-volume changes, hence pressure-volume work square4 -if work is done by system. square4 + if work is done on the system square4 Unit: J Heat > 0 Work > 0 Heat < 0 Work < 0
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1/7/2014 3 INTERNAL ENERGY -U Total energy stored in a thermodynamic system Thermal + nuclear interactions + chemical energy + other forms of energy found in the system Law of Conservation of ENERGY 1st Law of Thermodynamics "Energy can neither be created nor destroyed, but onlytransferred from one system to anotherand transformed from one form to another." or "The internal energy of an isolatedsystem isconstant (even though that energy may betransformed from one type to another)." ∆U = q + w Change in Internal Energy of system or ∆U: ∆U > 0 gain of energy ∆U < 0 loss of energy Changes in Internal energy Example: If 1200 joules of heat are added to a system and the system does 800 joules of work on the surroundings, what is the : 1. energy change for the system, Δ E sys ? 2. energy change of the surroundings, Δ E surr ? triangle45right Thermodynamicstate -set of conditions that specify all of the properties of the system. Examples - triangle45right The number of moles and identity of each substance. triangle45right The physical states of each substance. triangle45right The temperature of the system. triangle45right The pressure of the system. Thermodynamic Terms Isothermal : Constant temperature Isobaric : Constant pressure Isochoric : Constant volume Adiabatic : Zero heat flow (Q = 0)
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1/7/2014 4 State functions -properties of a system that depend only on the state (Initial and Final states) State functions are always written using capital letters.
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