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A 50.0 g ball is dropped from an altitude of 2.0 km. Calculate: U i, K max, & W done through the fall

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Chapter 12 Thermal Energy

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Thermodynamics The movement of heat

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Kinetic Theory 1)All matter is made up of tiny particles 2)All particles are in constant motion 3)All collisions are elastic

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Temperature A measure of average kinetic energy

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Temperature A measure of heat intensity

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Thermal Equilibrium When the average kinetic energy of two or more substances become equal; thus their particles have the same exchange rate

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Because it is a measure of average kinetic energy, temperature is related to the motion of particles (atoms, molecules, ions, etc)

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Thermometer A device, calibrated to some temp scale, that is allowed to come to thermal equilibrium with something else

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Temperature Scales Celcius ( o C) –Based on MP & BP of water Kelvin (K) –Based of absolute temperature

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Temperature Scales K = o C + 273

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Convert Temperatures 100 K = ___ o C 100 o C = ___ K

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Heat A form of energy that flows due to temperature differences

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Heat (Q) Because particle at higher temp. move faster than particles at a lower temp., the net flow of heat is H C

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Heat (Q) Heat will continue to have net flow from H C as long as there is a temperature difference

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Heat (Q) When there is no temperature differences, the system has reached thermal equilibrium

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Work The movement of energy by means other than temperature difference

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1 st Law of Thermo. The increase in thermal energy = sum of heat added & work done to a system

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1 st Law of Thermo. E = Q + W

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In Most Engines Heat is added by some high energy source (gas) Work is done by the engine

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In Most Engines E = Q + W But W < 0

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Entropy A measure of the disorder in a system

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2 nd Law of Thermo. In natural processes, entropy increases

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Entropy When fuel is burned, entropy is increased

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Specific Heat (C) The thermal energy required to raise 1 unit mass of matter 1 degree

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Specific Heat (C) The thermal energy required to raise 1 kg of matter 1 degree K

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Heat (Q or H) Heat transfer = mass x specific heat x the temperature change Q = mC T

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Calculate the heat required to raise 50.0 g of water from 25.0 o C to 65.0 o C. C water = 4180 J/kgK

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Calculate the heat required to raise 250.0 g of lead from -25.0 o C to 175.0 o C. C lead = 130 J/kgK

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28 kJ of heat was required to raise the temperature of 100.0 g of a substance from -125 o C to 575 o C. Calculate: C

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3.6 kJ of heat was required to raise the temperature of 10.0 g of a substance from -22 o C to 578 o C. Calculate: C

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Conservation of Heat The total energy of an isolated system is constant

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Conservation of Heat Because the total amount of heat is constant q or H system = 0

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Conservation of Heat q or H system = 0 H sys = H 1 + H 2 +.. q sys = q 1 + q 2 +..= 0

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Conservation of Heat q sys = q 1 + q 2 = 0 mC T 1 + mC T 2 = 0 mC T 1 = - mC T 2

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Conservation of Heat q sys = q gained + q lost q gained = - q lost mC T gain = - mC T lost

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A 50.0 g slug of metal at 77.0 o C is added to 500. g water at 25.0 o C. T eq = 27.0 o C. Calculate: C metal C water = 4180 J/kgK

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A 200.0 g slug of metal at 77.5 o C is added to 400. g water at 25.0 o C. T eq = 27.5 o C. Calculate: C metal C water = 4180 J/kgK

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Solving Mixture Temperatures q system = 0 q system = q hot + q cold mC T hot = -mC T cold T = T f – T i mC(T f – T i ) hot = -mC(T f – T i ) cold

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Conservation of Heat mC h T f - mC h T h +mC c T f - mC c T c = 0

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Conservation of Heat mC h T f - mC h T h = -mC c T f + mC c T c

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20.0 g of water at 25.0 o C is added to 30.0 g water at 75.0 o C. Calculate: T eq C water = 4180 J/kgK

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500. g of water at 75.0 o C is added to 300. g water in a 200. g calorimeter all at 25.0 o C. Calculate: T eq C water = 4180 J/kgK C cal = 1000 J/kgK

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A 500.0 g slug of metal at 87.5. o C is added to 4.0 kg water in a 1.0 kg can at 25.0 o C. T eq = 27.5 o C. Calculate: C metal C water = 4180 J/kgK C can = 1.0 J/gK

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States of Matter Solid Liquid Gas

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Solid Has definite size & definite shape Particles vibrate at fixed positions

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Liquid Has definite size but no definite shape Particles vibrate at moving positions

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Gas Has neither size nor shape Particles move at random

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Change of State When a substance changes from one state of matter to another

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Change of State Change of state involves an energy change

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Changes of State Melting-Freezing Boiling-Condensation Sublimation- Deposition

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Melting Point The temperature at which a solid is at dynamic equilibrium with its liquid. Freezing Point (Same)

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Boiling Point The temperature at which a liquid is at dynamic equilibrium with its gas. Condensationing Point (Same)

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Changes of State During changes of state, the temperature remains constant; all energy is used to change the state

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Heat of Fusion (H f ) The heat required to melt one unit mass of a substance at its MP

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Heat of Fusion (H f ) H f water = 3.34 x 10 5 J/kg H f water = 334 J/g

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Heat of Vaporization (H V ) The heat required to vaporize one unit mass of a substance at its BP

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Heat of Vaporization (H V ) H v water = 2.26 x 10 6 J/kg H v water = 2260 J/g

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Change of State q = mH

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Changes of State q f = mH f q v = mH v

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Calculate the heat required to change 250 g ice to water at its MP: H f = 3.34 x 10 5 J/kg

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Calculate the heat required to boil 400 g of water at its BP: H V = 2.26 x 10 6 J/kg

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Calculate the heat change when the temperature of 2.0 kg H 2 O is changed from 50 o C to 150 o C:

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Calculate the heat change when the temperature of 4.0 kg H 2 O is changed from -25.0 o C to 125.0 o C:

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Constants for Water H f = 3.34 x 10 5 J/kg H v = 2.26 x 10 6 J/kg C ice = 2060 J/kgK C water = 4180 J/kgK C steam = 2020 J/kgK

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1 st Law of Thermo Total E equal work done plus heat added to it E = Q + W

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Heat Engine Any engine that converts heat energy to mechanical energy (Steam, internal combustion, etc.)

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Heat Pumps & Refrigerators Use pressure changes & the heat of vaporization to transfer heat from cold to hot

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2 nd Law of Thermo The total entropy of an isolated system always increases

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20.0 g of lead at 75.0 o C is added to 100.0 g water at 25.0 o C. Calculate: T eq C water = 4180 J/kgK C lead = 130. J/kgK

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50.0 g of milk at 5.00 o C is added to 500.0 g coffee in a 400.0 g cup at 75.0 o C. Calculate: T eq C coffee = 4.00 J/gK C cup = 1.50 J/gK C milk = 3.50 J/gK

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T i = 25.0 o C T f = 200.0 o C BP = 100.0 o C MP = 0.0 o C Mass of H 2 O = 5.00 kg Calculate: Q total C ice = 2.06 J/gK, H v = 2260 J/g C water = 4.18 J/gK, H f = 334 J/g C steam = 2.02 J/gK

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T i = -50.0 o C T f = 300.0 o C BP = 100.0 o C MP = 0.0 o C Mass of H 2 O = 5.00 kg Calculate: Q total C ice = 2.06 J/gK, H v = 2260 J/g C water = 4.18 J/gK, H f = 334 J/g C steam = 2.02 J/gK

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20.0 g of lead at 75.0 o C is added to 100.0 g water at 25.0 o C. Calculate: T eq C water = 4180 J/kgK C lead = 130. J/kgK

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A 500.0 g slug of metal at 86.5. o C is added to 4.0 kg water in a 2.0 kg can at 24.0 o C. T eq = 26.5 o C. Calculate: C metal C water = 4180 J/kgK C can = 1.0 J/gK

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A 50.0 g of ice at -20.0 o C is added to 2.0 kg water in a 1.0 kg can at 25.0 o C. Calculate: T eq C w = 4180 J/kgK C c = 1.0 J/gK C ice = 2.06 J/gK H f = 340 J/g

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A 50.0 g of steam at 120.0 o C is added to 2.0 kg water in a 1.0 kg can at 20.0 o C. Calculate: T eq C w = 4180 J/kgK C c = 1.0 J/gK H V = 2260 J/g

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A 400.0 g of steam at 125.0 o C is added to 2.0 kg ice in a 1.0 kg can at -20.0 o C. Calculate: T eq Constants will be on the board

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