Thermodynamics

Announcements – 1/21 Next Monday, 1/26 – Readiness Quiz 1 –Chapter 19, sections 1 – 4 –Chapter 20, sections 1 – 4 Next Wednesday, 1/28 – First Quiz –Probably Chapter 17 Next Friday, 1/30 – First Homework –Getting used to WebAssign, chapters 17, 18, 19

More Announcements Homework: on WebAssign –Site: –Login: eLearn username –Institution: TSU –Password: Tigers –You ’ ll need to pay by Friday, January 30 th Readiness Quizzes: On eLearn –Due before class starts on the due date

17-1: Temperature and Thermal Equilibrium “ Hot ” and “ Cold ” Thermal equilibrium

The illustration shows a thermometer that uses a column of liquid (usually mercury or ethanol) to measure air temperature. In thermal equilibrium, this thermometer measures the temperature of 1. the column of liquid. 2. the glass that encloses the liquid. 3. the air outside the thermometer. 4. both 1. and all of 1., 2., and 3.

17-4: Thermal Expansion Most stuff expands when heated

1. illustration #1 2. illustration #2 3. The answer depends on the material of which the object is made. 4. The answer depends on how much the temperature increases. 5. Both 3. and 4. are correct. A solid object has a hole in it. Which of these illustrations more correctly shows how the size of the object and the hole change as the temperature increases? #1 #2

17-5: Quantity of Heat Heat is another form of energy But heat is always energy transfer Changes of temperature indicate changes in heat

17-5: Specific Heat Connects heat transfer to temperature change

17-7: Conduction Heat transfer through a material

17-7: Convection Heat transfer by fluid motion

17-7: Radiation Heat transfer by electromagnetic waves

The heat that is transferred between the sun and the earth is transferred by: 1.Conduction 2.Convection 3.Radiation 4.Both 2 & 3 5.1, 2 & 3

18-3: Kinetic-Molecular Model Describe pressure, etc. in terms of molecular motions Find that average kinetic energy of molecules depends only on temperature Why is hydrogen so rare on earth?

Consider two specimens of ideal gas at the same temperature. The molecules in specimen #1 have greater molar mass than the molecules in specimen #2. How do the rms speed of molecules (v rms ) and the average translational kinetic energy per molecule (KE) compare in the two specimens? 1. v rms and KE are both greater in specimen #2. 2. v rms is greater in specimen #2; KE is the same in both specimens. 3. v rms is greater in specimen #2; KE is greater in specimen #1. 4. Both v rms and KE are the same in both specimens. 5. None of the above is correct.

19-1: Thermodynamic Systems We ’ re going to be talking about engines and such – we ’ ll call them thermodynamic systems

19-1: Sign of Q and W

19-2: Work done during volume changes

19-2: Finding the work

19-3: Paths

19-4: First Law of Thermodynamics You can ’ t win, you can only break even

19-4: Cyclic Processes

Example 19.4 A series of thermodynamic processes is shown in the pV diagram. In process ab, 150 J of heat is added to the system, and in process bd, 600 J of heat is added. –Find the internal energy change in ab –Find the internal energy change in abd –Find the total heat added in acd

A system can be taken from state a to state b along any of the three paths shown in the pV– diagram. If state b has greater internal energy than state a, along which path is the absolute value |Q| of the heat transfer the greatest? 1. path 12. path 23. path 3 4. |Q| is the same for all three paths. 5. not enough information given to decide

In an isothermal expansion of an ideal gas, the amount of heat that flows into the gas 1. is greater than the amount of work done by the gas. 2. equals the amount of work done by the gas. 3. is less than the amount of work done by the gas, but greater than zero. 4. is zero. 5. is negative (heat flows out of the gas).

20-1: Irreversible Processes You can never run a process completely in reverse Closest you can get is quasi-static equilibrium

20-2: Heat Engines A device that transforms heat partly into work or mechanical energy

20-3: Internal Combustion Engines

20-4: Refrigerators

Short-Term Fix? Your air conditioner is broken, but it ’ s very hot! As a short-term fix, you just open the door of the refrigerator. As it runs, does your kitchen: 1. get warmer 2. get cooler 3. stay at the same temperature

20-5: The Second Law of Thermodynamics 1 st Law: You can ’ t win, you can only break even 2 nd Law: Actually, you can ’ t even break even

20-6: The Carnot Cycle

20-7: Entropy A quantitative measure of disorder Entropy is constant or increases in every process (if you really count all the systems taking part)

Entropy

Ice Cubes You put a tray of water in the freezer, and it turns to ice. Has the entropy of the universe: 1. Increased 2. Decreased 3. Remained the same