Thermodynamics. 1 st law of thermodynamics Energy may be converted to different forms, but it is neither created nor destroyed during transformations.

Slides:



Advertisements
Similar presentations
IB Physics Topic 3 & 10 Mr. Jean May 7 th, The plan: Video clip of the day Thermodynamics Carnot Cycle Second Law of Thermodynamics Refrigeration.
Advertisements

Chapter 6 Thermal Energy
Heat Chapter 9 &10. Kinetic-molecular Theory Matter is made up of many tiny particles that are always in motion In a hot body the particles move faster.
The Second Law of Thermodynamics Physics 102 Professor Lee Carkner Lecture 7.
Conservation of Energy
Chapter 16: Temperature and Heat. Heat Thermal energy that flows from something of high temp. to something of low temp. Warm  Cold Metric unit  Joules.
The Second Law of Thermodynamics Physics 102 Professor Lee Carkner Lecture 7.
Introduction to Thermodynamics Unit 03 - Thermodynamics.
Family Homecoming Special Event "Can Climate Engineering Serve as a Complementary Step to Aggressive Mitigation?" ¨Dr. Michael MacCracken, The Climate.
Thermal Energy and Matter
Introduction to Thermodynamics
Important Terms & Notes Conceptual Physics Mar. 12, 2014.
Introduction to Thermodynamics
Energy. The Nature of Energy What is energy? Electrical Energy Energy is the ability to cause a change or the ability to do work What are the different.
Physics Lecture Notes The Laws of Thermodynamics
Chapter 18 Temperature, Heat, and the First Law of Thermodynamics.
Energy & Its Impact on Global Society Jerome K. Williams, Ph.D. Saint Leo University Dept. Mathematics & Sciences.
The Laws of Thermodynamics
Chapter 6 Thermal Energy. 6 – 1 Temperature and Thermal Energy.
L 20 Thermodynamics [5] heat, work, and internal energy
L 20 Thermodynamics [5] heat, work, and internal energy heat, work, and internal energy the 1 st law of thermodynamics the 1 st law of thermodynamics the.
ThermodynamicsThermodynamics. Mechanical Equivalent of Heat Heat produced by other forms of energy Heat produced by other forms of energy Internal Energy:
Changes of Phase List the four phases of matter in order of increasing internal energy.
Chapter 12 Thermal Energy Glencoe 2005 Honors Physics Bloom High School.
Second Law of Thermodynamics.  No cyclic process that converts heat entirely into work is possible.  W can never be equal to Q.  Some energy must always.
Physics 101: Lecture 28, Pg 1 Physics 101: Lecture 28 Thermodynamics II l Today’s lecture will cover Textbook Chapter Final.
Laws of Thermodynamics Thermal Physics, Lecture 4.
Heat Engines and The Carnot Cycle. First Statement of the Second Law of Thermodynamics The first statement of the second law is a statement from common.
ENERGY. What is Energy? The ability to do work or cause change It occurs in different forms: –Electrical, chemical, light, mechanical Energy comes in.
Important Terms & Notes Conceptual Physics Mar. 17, 2014.
5.3 Essential Questions What are the first and second laws of thermodynamics? How does an internal combustion engine work? How does a refrigerator work?
HEAT & THERMAL ENERGY CH. 16. State indicator 17. Demonstrate that thermal energy can be transferred by conduction, convection or radiation (e.g., through.
Physics 101: Lecture 28, Pg 1 Physics 101: Lecture 28 Thermodynamics II l Today’s lecture will cover Textbook Chapter Final Check Final Exam.
Thermodynamics Physics H Mr. Padilla Thermodynamics The study of heat and its transformation into mechanical energy. Foundation – Conservation of energy.
Heat and the 2 nd Law of Thermodynamics.  Although we learned in the first law that the total amount of energy, including heat, is conserved in an isolated.
The Zeroth Law of Thermodynamics
Thermal Radiation Thermal radiation is energy transfer by electromagnetic waves All objects emit thermal radiation The hotter an object is, the more thermal.
Temperature and Heat. Temperature Kinetic energy is the energy that matter has due to the movement of that matter or within the matter Kinetic energy.
Chapter 12: Thermal Energy What’s hot and what’s not…
Unit 6. Temperature Temperature – A measure of the average kinetic energy of the particles in an object (how hot or cold). There are three common temperature.
Thermodynamics Internal energy of a system can be increased either by adding energy to the system or by doing work on the system Remember internal energy.
First Law of Thermodynamics  The first law of thermodynamics is often called the Law of Conservation of Energy.
Chapter 5 Thermal Energy
Thermal Energy & Heat Heat and Its Uses. Thermal Energy & Heat 16.1 Thermal Energy and Matter.
Power use per person per day, by Country (2007) Why do we use the unit of the “Joule”?
L 20 Thermodynamics [5] heat, work, and internal energy heat, work, and internal energy the 1 st law of thermodynamics the 1 st law of thermodynamics the.
Chapter 5.4 Notes Thermal Energy. Thermal Energy is the total kinetic energy of the motion of atoms in an object. Molecules in an object are constantly.
Chapter 11 Laws of Thermodynamics. Chapter 11 Objectives Internal energy vs heat Work done on or by a system Adiabatic process 1 st Law of Thermodynamics.
Chapter 12 Thermal Energy.
L 20 Thermodynamics [5] heat, work, and internal energy heat, work, and internal energy the 1 st law of thermodynamics the 1 st law of thermodynamics the.
Physics 101: Lecture 28, Pg 1 Physics 101: Lecture 28 Thermodynamics II l Today’s lecture will cover Textbook Chapter Final Check Final Exam.
Physics 101: Lecture 28, Pg 1 Physics 101: Lecture 28 Thermodynamics II l Today’s lecture will cover Textbook Chapter
THERMODYNAMICS Thermodynamics Thermodynamics is the study of heat. Kinetic-Molecular Theory - matter is made up of tiny particles in motion. In hot objects.
Physics 101: Lecture 26, Pg 1 Physics 101: Lecture 26 Thermodynamics II Final.
Thermodynamics II Thermodynamics II. THTH TCTC QHQH QCQC W HEAT ENGINE THTH TCTC QHQH QCQC W REFRIGERATOR system l system taken in closed cycle   U.
Lecture 26: Thermodynamics II l Heat Engines l Refrigerators l Entropy l 2 nd Law of Thermodynamics l Carnot Engines.
Chapter 12 Laws of Thermodynamics. Chapter 12 Objectives Internal energy vs heat Work done on or by a system Adiabatic process 1 st Law of Thermodynamics.
Introduction to Thermodynamics Principles of Engineering 1.
Unit 61: Engineering Thermodynamics Lesson 8: Second Law of Thermodynamics.
KIMIA LINGKUNGAN BAGIAN 2: TERMODINAMIKA. PREVIEW In this third part of the course we:  define and apply a number of thermodynamic ideas and concepts.
Chapter 16 Thermal Energy & Heat.  Objectives:  1. Explain how heat and work transfer energy  2. Relate thermal energy to the motion of particles that.
Thermal Energy and Heat. Temperature Temperature is a measure of the average kinetic energy of the individual particles in matter. The higher the temperature,
Energy and Heat Mr. T Gainesville Middle. What is Energy? Energy is defined as the ability to do work. The metric unit for energy is the joules (J)
It’s all about energy. Energy and its transfer controls Earth’s systems.
Lecture 27Purdue University, Physics 2201 Lecture 27 Thermodynamics II Physics 220.
16.2 Heat and Thermodynamics Conduction Conduction is the transfer of thermal energy with no overall transfer of matter. Conduction in gases is slower.
Chapter 16 Thermal Energy and Heat
HT1 01 – Introduction to Energy, heat, and temperature
Energy.
Energy and the Ocean 7 October 2014.
Presentation transcript:

Thermodynamics

1 st law of thermodynamics Energy may be converted to different forms, but it is neither created nor destroyed during transformations Energy from chemical bonds is converted to kinetic energy and heat (body and friction from tires) Amount of energy before and after transformation is the same, only the form of the energy has changed ENERGY Heat

1 st Law (Contd.) Another way to state the 1 st law is mathematically.  E = Q + W This equation says that the only way to change the energy of a system is to add heat to it (Q) or to do work on it (W) Example: Can make wood hotter by applying fire or hitting

Heat Heat - the ENERGY transferred between objects of different temperature While used a lot in our vocabulary, this term is very misunderstood Heat is NOT temperature. An object CANNOT contain heat; objects contain thermal energy. Heat is a very important type of energy transfer

Heat Versus Temperature Temperature - the property that two objects have in common when NO heat is transferred between them Temperature is a relative property. We define it in relationship to other things T 1 > T 2 T 1 = T 2

Heat Flow 1.Conduction - energy transfer by next-nearest molecule interaction 2.Convection - energy transfer by mixing; can be natural or forced (fan, stirring, etc.) 3.Radiation - energy transfer by electromagnetic radiation Heat can flow via one of three methods

Conduction Energy transfer by nearest molecules running into each other Rate of heat transfer depends on Temperature difference  T = T H - T C Thickness of material L Thermal conductivity of material k Surface area A Q k  T A t L =

Conduction Q  T A t R = More familiar If intervening material is made up of more than one substance, add R-values R total = R 1 + R 2 + R 3 + …. Problem: How is the rate of heat transfer affected by adding an R-value 8 insulation to an 8’x20’ wall that has an R-value of 12 when the temperature difference is 20 o F?

Convection Heat transfer via mixing; requires some type of fluid (gas, liquid) Things can naturally convect, especially when density changes and more buoyant materials will rise Forced convection requires energy input

Radiation Every object in the universe emits electromagnetic radiation because it has a temperature above absolute zero. Type of radiation depends upon the value of the temperature Wein’s Law => max =.003 m K T Problem: At what wavelength do you emit most of your radiation?

Stefan-Boltzmann Law The rate of heat emission due to radiation depends on size and temperature. Q/t = e  A T 4 where e is the emissivity of the object Remember, the object will be absorbing radiation while it is emitting. Therefore, the total heat transfer is Q/t = e  A (T object 4 - T surroundings 4 )

Heat Transfer Devices Heat PumpHeat Engine Transfers heat from cold to hot using external energy W Example: Refrigerator Outputs useful energy W by extracting it from heat passing from hot to cold Example: Car engine In both devices, Q H = Q C + W

If energy is never created or destroyed, why can’t we keep reusing the same energy source forever? ANSWER : Although energy isn’t destroyed, in every energy transfer, some of it will change to a non-usable form This is a consequence of the 2 nd law of thermodynamics “In a closed system, the total entropy either increases or stays the same” 2 nd law of thermodynamics

Second law of thermodynamics ENERGY Waste Heat When a chemical bond is broken, you get some high quality ENERGY capable of doing work, and some low quality “wasted” energy No energy was lost or created in the transfer, but the usability of the energy declined in the transformation. This low quality energy cannot be effectively harnessed to do any more work, so you cannot use one energy source forever

Example: powering your car Breaking chemical bonds in gas during combustion yields high quality energy which produces kinetic energy to move car Also produces waste energy as heat with little ability to do work Second law of thermodynamics

Combustion of gasoline Piston movement Axle turns Wheels turn Heat loss during combustion E Friction with pistons E Friction with axle E Friction of tires with road E EE EE Energy in gasoline Amount of high quality energy declines with each step (width of orange arrows) No energy is lost, it simply is converted to low- quality heat that cannot be used for further work Usable E

Efficiency A measure of how well energy is converted Efficiency = useful energy out total energy input Examples Internal combustion engine car is about 10% efficient Electric car is about 20% efficient Incandescent light bulb is about 1% efficient

Efficiency Example A power plant consumes 80,000 Joules of coal energy to produce 30,000 Joules of electricity. What is the efficiency? Efficiency = 30,000 J 80,000 J =.375 = 37.5 % = 10,000 J

Heat Engine Efficiency Energy input = Q H Usable energy output = W Efficiency = W QHQH Since Q H = Q C + W => W = Q H - Q C Efficiency = 1 - QCQC QHQH Problem: A car takes in 20,000 J of gasoline and outputs 19,000 J of heat. What is the efficiency of the car?

Heat Pump COP For heat pumps, it is not proper to discuss efficiency since there is no “usable energy ouput”. Instead, define “coefficient of performance” to discuss how much energy it moves per energy paid for. COP heater = COP a.c. = QHQH W QCQC W Note: COP heater is always greater than 1. Why?

Maximum Efficiency Unfortunately, the 2nd law of thermodynamics limits the maximum efficiency that a device can have. No device will ever be 100% efficient. For a heat engine, the limit is given by Maximum efficiency = 1 - TCTC THTH where T C is the temperature of the cold reservoir and T H is the temperature of the hot reservoir in the Kelvin temperature scale

Maximum Efficiency Example An inventor proposes a heat engine that will produce electricity by extracting heat from ocean surface water at 20 o C (293 K) and dumping the waste heat to the deep ocean at 5 o C (278 K). What is the maximum efficiency? Maximum efficiency = K 293 K = =.05 At most, this device will be 5% efficient. In reality, it will probably only be about half of this, or 2-3% efficient.

Recapping 2nd LAW : Energy is transformed from high quality to low quality 1st LAW : Energy is neither created nor destroyed, only transformed RESULT : Low quality heat cannot do substantial work, requiring a new source of high quality energy