ThermodynamicsSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36ThermodynamicsThermodynamics is the study of the transformation of energy into heat and workEnergy can be used -to provide heat-for mechanical work -to produce electric work -to sustain lifeCH4(g) + 2 O2(g) --> CO2(g) + 2 H2O(g) + HEATThe result of breaking C-H and O-O bonds and formation of C-O and H-O bonds is heatWhy is propane (C3H8) a better fuel than benzene (C6H6)?What compounds are feasible as alternate fuels?Why are carbohydrates, proteins and fats fuels for our bodies?Why is ATP (adenosine triphosphate) an “energy-rich” molecule?Terminology - System, Surroundings & State FunctionsSystem: object under observation.In a chemical reaction, the reaction mixture is the system.Surrounding - everything else not considered to be the system.System Energy MatterTransfer between system and surroundingOpenYes YesClosedYes NoIsolatedNo NoState: macroscopic, measurable properties, like composition, volume, pressure, temperature, which define a system.Process - the path the system undergoes to change from an initial state to a final state.EnergyEnergy: capacity to do workUnits of energy 1 Joule (J) = 1 kg m2 s-2Objects can posses energy either as kinetic energy (KE) or potential energy (PE).Kinetic energy: energy of motionEK = 1/2 mv2Potential energy: energy a body possesses on account of its position in a field of force.PE depends on the nature of the force being felt by the body. for example, electrostatic force, gravitational forceEP = m g h (for a body experiencing a gravitational force)Total Internal Energy (E) = EK + EPEnergy, Work and HeatEnergy is the capacity to do work or transfer heat.Work : Energy used to move an object.Heat : Energy transferred from a hotter body to a colder body.WorkWork : movement against an opposing forceWork is done when a weight is raised against gravity.The reaction in a battery does work when it pushes electrons through a circuit.The hot gas mixture in the cylinder of an automobile engine does work when it pushes back the piston.Work (w) = force x distanceUnits: 1 J = 1 kg m2 s-2The total capacity of a system to do work is its INTERNAL ENERGY, E.Ewound spring > Eunwound spring Ecompressed gas > Eexpanded gas Echarged battery > Edischarged battery CHANGE in internal energy E = Efinal - EinitialWhen the transfer of energy is only as work, E = wWhen work is done by the system, w < 0When work is done on the systen, w > 0HeatHeat (q) is energy transferred as a result of a temperature difference.Energy flows as heat from a high temperature region to a low temperature region.Units of Heat: Joule (J)1 calorie (cal) = 4.184 J(nutritional calorie (Cal) = 1000 cal = 4184 J or 4.184 kJ)Heat is the transfer of energy as a result of a temperature difference.When the only transfer of energy is as heat, E = qIf energy enters the system as heat, q > 0If energy leaves the system as heat, q < 0Heat, and hence changes in internal energy, accompany almost all chemical reactions. When a chemical reaction occurs by absorbing heat from its surroundings, the reaction is said to be endothermic.When a chemical reaction is accompanied by the release of heat, the reaction is said to be exothermic.Closed System (exchange of energy but not matter)A closed system with thermally insulating walls - ADIABATICNo flow of energy as heat into or out of the system. However, energy may be transferred into or out of the system as work.A closed system which permits transfer of energy as heat - NONADIABATIC.The First Law of Thermodynamics1) Energy is conserved2) Heat and work can produce equivalent effects3) The only way that energy can be transferred is through heat and work.First Law E = q + wwhereE is the change in internal energy of a system that is not isolatedq is the heat involved during the processw work done during the processNote: the internal energy of an ISOLATED system is constantAnimationSign conventionIf heat flows into the system q > 0Heat flows out of the system q < 0Work done by the system w < 0Work done on the system w > 0E is a state function; the change in E depends only on the initial and final energies of the system and not on the details of the process.q and w are PATH FUNCTIONS.w > 0 w = 0A gas at 25oC expanding at constant temperature (isothermal) by 100 cm3 by two different paths between the same initial and final states are the samemechanical work = force x distanceIf the direction of the applied force is in the same direction as the displacement, work is done on the body; w > 0If the direction of the applied force is opposite to the direction of the motion of the body, work is done against the body ; w < 0Mechanical Work12w = KE =  ( m v2)The work done in raising an object from one height to another changes the potential energy of the objectw = PE = m g hThe work done in stopping a moving object, or pushing an object causes a change in the kinetic energy of the systemWork done in expanding a gas against an external pressure, or to compress a gas causes a change in volume.w = - Pext V (constant P)where V = Vfinal - VinitialIf the gas expands V > 0 => work done by the gas (pushes against surrounding); work < 0If the gas is compressed V < 0 => work done on the gas (by the surrounding); work > 0Pressure-Volume Workw = - Pext Vw = Force x distanceF = Pressure/Areaw = d Pext AV = d AProblem:A gas expands against a constant pressure of 5.00 atm, from 10.00 to 20.00 L, absorbing 2.00kJ of heat. Calculate the work done and the change in the internal energy of the gas.1 L-atm = 101.3 Jw = - Pext V= - (5.00 atm) (20.00 L - 10.00 L) = - 50.0 L-atm or - 5.06 kJE = q + w = 2.00 kJ + (-5.06 kJ) = -3.06 kJFor a process which takes place at constant volumew = - Pext V = 0; if volume is constantE = q + wFor constant volume processes, no work can be doneE = qvwhere qv is the heat exchanged at constant volumeIf the external pressure is 0 (a vacuum), w = 0A system does no expansion work when it expands into vacuum (free expansion).CalorimetryCalorimetry is the measurement of the amount of heat flow and change in temperature accompanying a process.Transfer of energy as heat accompanying a process can be measured in a