Slide 1Slide 2Slide 3Slide 4Thermal EquilibriumExothermicSlide 7EndothermicSlide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Heating curveSlide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Thermochemical EquationsSlide 51Slide 52Slide 53Slide 54Slide 55Slide 56Slide 57Slide 58Slide 59Slide 60Hess’s LawSlide 62Slide 63Slide 64Enthalpy change for a reactionHess’s LawSlide 67Slide 68Slide 69Slide 70Slide 71Formation ReactionsSlide 73Slide 74Ch. 5 Principles of Chemical Reactivity: Energy and Chemical ReactionsThermodynamics: the science of heat and work;the study of energy changes that accompany physical and chemical processes (usually involves heat hence thermo)5.1 Energy: Some Basic PrinciplesEnergy: capacity to do work2 basic categories of energy:1. Potential energy: energy that results from an object’s position2. Kinetic energy: energy associated with motionLaw of Conservation of Energy: Energy can neither be created nor destroyed. The total energy of the universe is constant.SI unit for energy is the joule (J)Systems and SurroundingsSystem: is defined as an object, or collection of objects, being studied, e.g. in the lab it can be what you are doing in the beakerSurroundings: include everything outside the system (e.g. outside of the beaker)Energy flows between the two.Directionality and Extent of Transfer of Heat: Thermal Equilibrium•Energy transfer as heat will occur spontaneously from an object at a higher temperature to an object at a lower temperature. •Transfer of energy as heat continues until both objects are at the same temperature and thermal equilibrium is achieved.•At thermal equilibrium, the object with a temperature increase has gained thermal energy, the object with a temperature decrease has lost thermal energy.Thermal EquilibriumClicker Q: What is loosing heat? A. water B. metal•When energy leaves the system and goes into the surroundings, the process is said to be EXOTHERMIC. ∆H = enthalpy (negative), q = heat (negative)•In the case of thermal energy, the temperature of the system decreases. (qsystem < 0) and thus the T of the surroundings increases.•Tsystem = (Tfinal – Tinitial) < 0ExothermicExothermicReactants → products + heatKey phrases: heat evolved; heat/energy transferred from system to surroundingsmoles 6 moles 5 moles 8 mole 1kJ 3523 OH 6 CO 5 O 8 HC)(22(g)2(g))12(5kJ 3523 - H OH 6 CO 5O 8 HCorxn)(22(g)2(g))12(5•When energy enters the system from the surroundings, the process is said to be ENDOTHERMIC. ∆H = enthalpy (positive) q = heat (positive)•In the case of thermal energy, the temperature of the system increases (qsystem > 0) and the surroundings decreases.•Tsystem > 0EndothermicEndothermicReactants + heat → productsKey phrases: heat absorbed, heat/energy transferred from surroundings to systemH2O → H2 + ½ O2 ∆H = 241.82 kJ/molH2O + 241.82 kJ/mol → H2 + ½ O2Clicker Q: A. exothermic B. endothermicCO(g) + Cl2(g) → COCl2(g) heat evolved (q) is 108 kJ5.2 Specific Heat Capacity: Heating and CoolingWhen an object is heated or cooled, the quantity of energy transferred depends on 3 things:1. Quantity (mass) of material2. Magnitude of T change3. Identity of material gaining or losing energy= ´ ´ Dq m C TSpecific heat capacity (c): the energy transferred as heat that is required to raise the T of 1 g of a substance by 1 K (or 1°C); units of J/gK or J/g°C; intensive property= ´ ´ Dq m C Tq: energy gained or lostm: massC: specific heat capacity (J/g°C or J/gK or J/molK etc)∆T: change in T, Tfinal – T initialMolar heat capacity: heat capacities can be expressed on a per mole basis; J/mol K or J/mol°CIn the laboratory a student finds that it takes 62.4 Joules to increase the temperature of 10.2 grams of solid iron from 23.2 to 37.9°C.What is specific heat capacity (c) of Fe?Clicker Q: Specific heat capacity of Cu is 0.385 J/gK. How much energy is required to heat 200. g of Cu from 25.0°C to 50.0°C? enter in JDetermine the final temperature of a 25.0 g block of metal that absorbs 255 cal of energy. The initial temperature of the block was 17.0°C.The specific heat capacity of the metal is:J2.72 g C��Clicker Q: A sample of solid platinum (c = 0.519 J/g°C) is heated with an electrical coil. If 25.5 Joules of energy are added to a 10.9 gram sample and the final temperature is 38.0oC, what is the initial temperature of the platinum?Quantitative Aspects of Energy Transferred as Heat55.0 g of iron at 99.8 °C is placed into 225 g water initially at 21.0 °C.•At thermal equilibrium, the water and iron are both at 23.1 °C.•What is the specific heat capacity of the metal?55.0 g of iron at 99.8 °C is placed into 225 g water initially at 21.0 °C (final T = 23.1°C). What is the specific heat capacity of the metal?Clicker Q: A 20.0 g piece of metal at 203°C is dropped into 100.0 g of water (4.184 J/g°C) at 25.0°C. The water T rises to 29.0°C. Calculate the specific heat of the metal (assume no heat losses to the surroundings).You mix 2 water containers: one is 100.0 g of water at 90.0°C and the other is 50.0 g at 50.0°C. What is the final temperature of the water. (specific heat for water is 4.184 J/g °C)5.3 Energy and Changes of StateChange of state: solid to liquid to gas etcSolid to liquid to gas requires an input in energy to overcome the attractive forces of the molecules/atoms. So endothermic.Temperature is constant throughout a change of state. Solid → liquid melting TWhat is endothermic? What is exothermic?Heat of vaporization (∆Hvap): the heat required to convert a substance from the liquid to the gas state all at the same T, units do not include T, because it happens at constant T (melting T); for water ∆Hfus = 333 J/gHeat of fusion (∆Hfus): the heat required to convert a substance from the solid to the liquid state all at the same T; units do not include T; for water ∆Hvap = 2256 J/g  J 2260-o(g)2J 2260o)(2C100.0at OH g 00.1C100.0at OH g 1.00Heating curve for water27Heating curveDo blank heating curve.1. Where is T = bp, mp?2. Where is ∆Hfus used?3. Where is c(solid) used?q(heating or