Detailed Outline for Chapter 12: Matter, Heat and Temperature

What was in ToC:

Heat and Temperature

In the previous chapters, we discussed the basic energy model, but concentrated mainly on mechanical energies. We occasionally used internal or thermal energy. This Chapter 12 now answers the questions What is thermal energy? and What does it mean to be “hot”, that is, what is temperature? One key strategic question is how to think about temperature. Should we tie it in with the microscopic model of average KE? Or just discuss it in terms of “hot” and “cold,” and then move on to thermometers (which is the standard approach)?

In any case, we can discuss thermal energy as an internal energy of the system, and the following topics:

  • Zeroth Law
  • Temperature & Temperature Scales
  • Gas Laws, absolute zero
  • Thermal Expansion
  • Heat & Work
  • Units of heat
  • Mechanical equivalent of heat
  • Specific Heat
  • Conduction, Convection, Radiation
  • Phase changes & Latent Heat
  • Kinetic theory of gases
  • Diffusion

We also add the following comments from Knight: “Needs thermal expansion, which PSE doesn't cover, but that can be grouped with temperature changes and phase changes under the general heading "consequences of heat." Also needs explicit coverage of heat conduction, convection, and radiation, which PSE lacks.” This chapter may seem like a bit of a grab bag of unrelated topics, but these are all topics that fit nicely under this basic heading and that the students really need to know.

Change in Title

Initially, the “Using Energy” chapter wasn’t to cover too much about temperature and temperature scales, the gas laws, or the relationship between heat and work, but, as writing proceeded, these topics needed to be moved into this chapter. The title “Heat and Temperature” no longer is a good fit; instead, we are using the title “Matter, Heat and Temperature” as the chapter is largely about matter (specific heat, expansion, phase changes, and—for gases—pressure or volume changes.) This will make it a nicer fit for a part titled “Properties of Matter” as well.

Theme of Chapter

The “grab bag” nature of the chapter will be minimized if we keep returning to the atomic view of matter that underlies and explains things. This will be a theme to which we continually return throughout the chapter.
Coverage

Coverage of topics in this area is quite standard among different books; where in the book these topics appear is not. There is quite a bit of variability in terms of where certain topics appear, the ordering of topics, and the overall themes of chapters. A few examples:

  • Walker does elasticity and stress and strain in the same chapter with the ideal gas law.
  • Calorimetry is treated very early in some books, much later in others.
  • Giancoli starts with an atomic theory of matter, and makes connections of temperature to motion of atoms early; Walker leaves this connection until later.

Other examples can be gleaned from the table on the next page, which shows a topic comparison among books. The first column shows the standard topics that all (or most) books do, the following columns show the relevant chapters in different books. The ordering of topics in KJF doesn’t stand out as being different from a “standard” treatment. The biggest difference between KJF and the other books is that KJF puts the laws of thermodynamics earlier, before other topics such as thermal expansion—but it makes a great deal of sense to tie these more closely to energy.

Other books devote more chapters to thermal physics (3 or 4), but some of them are quite brief. (Cutnell’s Chapter 13 on Heat Transfer is only 20 pages long, including problems and such.) KJF will have two chapters on thermal physics, but this should suffice. By putting the laws of thermodynamics in Chapter 11, right after a discussion of energy, some efficiency is possible. The other books have a fair amount of repetition; for instance, thermal energy concepts may be introduced repeatedly. We can avoid much of this. In addition, KJF will us a common atomic model throughout this chapter, which will allow more rapid development of topics such as thermal expansion, another efficiency.


12

Matter, Heat and Temperature

CO Photo Idea:

Elephant thermograph showing heat from ears. “How does an elephant keep cool in the hot African sun?”

Intro material: be sure to note strong connection to atomic model that will guide us in this chapter.

[What other ideas for photos? Need living world, connection to material of chapter. This one is a good example as it connects with the material of the previous chapters and poses a question that is answered later in the chapter.]

[In what follows, more examples are included than can be used. As the chapter is written, ones that don’t fit can be turned into EOC problems.]

12.1 An Atomic View of Heat and Temperature

Outline with PSE Material to Use:

Ch. 11 did a good deal with what thermal energy in gases looked like, but not much with solids. Start with a quick review of energy in general and thermal energy in particular, reminding folks of the atomic model, extrapolating to solids and liquids, and hinting at the notion of phase transitions. This will be a brief section that develops what will be a central theme in the chapter. It will be largely theoretical, with few examples. We will take the section on the atomic model from PSE:

Pages 513-514: Atomic model, including Figure 17.1

12.2 Thermal Energy and Specific Heat

Outline with PSE Material to Use:

In this section, we use the atomic model, showing the atomic basis of thermal energy for solids, liquids and gases. We show arguments for the form of specific heat for various materials, then give values in a table. For problems, we start with simple examples of adding energy to change temperature (e.g. kettle on stove) which makes a nice connection with the previous chapters. Then recall ideas of heat transfer in a thermal interaction from Chapter 12 (heat out of one object equals heat in the other), then segue to calorimetry—isolated systems, thermal interaction.

The specific heat treatment will combine and shorten two sections from PSE

Pages 527-529: Specific heat (general definition in terms of heat, temperature)

Pages 556-560: Specific heat (derivation of value for monatomic gases, plausibility argument for solids)

For practical problems of calorimetry, we can take over the relevant section of PSE:

Pages 531-532: Calorimetry, including determination of unknown metal.

Examples (in addition to appropriate ones in PSE):

  • How much energy is required to raise a person’s temperature when you have a fever?
  • How long does it take to heat up cup of water in microwave with a certain power input?
  • Conceptual example: Why use water in heating systems?
  • STT: four items, each gets same amount of heat; which one is at highest temperature?

FSA/TIY:

  • High specific heat of water: bodies of water moderate temperatures. Picture of lake with steam on cool morning, or perhaps thermograph of land/water at different times of day.

12.3 Kinetic Theory and The Gas Laws

Outline with PSE Material to Use:

In what follows, we want to use pressure, but we haven’t defined it yet, as fluids will be treated in Chapter 13. So we will need to start with a treatment of pressure.

Pages 447-449: Do definition of pressure, causes of pressure, pressure in gases.

In Chapter 11, we looked at the temperature of an ideal gas in some detail and even did an example of doing work on an ideal gas, but we didn’t do the gas laws in general. Strengthen the idea of using the atomic models as a basis for understanding by doing a quick derivation of gas laws from kinetic theory.

Start with conceptual overview: add more molecules, pressure goes up; make molecules closer together, pressure goes up; make temperature greater, pressure goes up. Present results in visual table showing examples. Then do the derivation:

Pages 550-553: Simplify this version of the derivation of relationship of pressure to speed.

Then recall from Chapter 11 the definition of temperature in terms of speed, and move on to ideal gas law:

Pages 498-501: Ideal gas law.

Add some examples here—e.g. mass of air in a 2l bottle.

Examples (in addition to appropriate ones in PSE):

  • Mass of air in 2l bottle—how much?
  • Constant volume gas thermometer.
  • Conceptual example: scuba divers have to exhale when coming to the surface.

FSA/TIY:

  • Weight of air. Bottle with air pumped in weighs more.
  • Chip bag, leave in sun. What happens?

12.4 Ideal Gas Processes

Outline with PSE Material to Use:

We looked at gases in Chapter 11, and introduced the ideal gas law, but we didn’t do much with thermal processes: isobaric expansion, etc. Take material from PSE from two sections: 16.6, 17.2. We will need to simplify and trim a good deal. This section should be a modest one.

Pages 501-505: Ideal gas processes; will need to simplify a bit. Mix in the pieces on the work done:

Pages 516-520: Work in ideal gas processes.

Close with a discussion of how to use an ideal gas in a heat engine:

Pages 578-580: A heat engine example.

Examples (in addition to appropriate ones in PSE):

  • “Inflate cold” on tires. How much difference does it make?
  • Compression of gas in cylinders of diesel engine.

FSA/TIY:

  • Fire cylinder—fast compression makes temperature that lights paper. Connect with the example on diesel engines.
  • Weather: rising, falling air masses and temp changes.

12.5 Thermal Expansion

Outline with PSE Material to Use:

Start with atomic view of solids; when you raise the temperature of a solid, atoms move around more, get farther apart. This leads to expansion. Can do a similar argument for liquids. This is a topic that receives scant coverage in PSE, so we will borrow the pieces we can, pieces dealing with the atomic model, pieces noting effects of expansion. We start by recalling the idea of how thermometers work using thermal expansion:

Page 491: Thermometers, expansion allows measurement of temperature. Add figures showing operation of alcohol thermometers, bimetallic strips.

Define variables and equations for linear and volume expansion, give table of values for various substances. Discuss the expansion of holes / interior volumes of containers—easy to show using atomic model.

Examples:

  • Height of Eiffel Tower vs. Temperature (linear expansion)
  • If the ocean heats up by 1°C, how much will the level rise? (volume expansion)
  • Conceptual example: radiator overflow. Radiator gets bigger... how come water flows out?
  • STT: Rod, length 1 m, heats up, length goes up by some amount. Another rod, length 2 m. Length goes up by how much?

FSA/TIY:

  • Heat ring to put around something, hole shrinks, tight fit. (Wagon wheel, or other modern practical example.)
  • Thermal expansion joints.
  • Accurate pendulum clocks—combine materials with different thermal expansion.
  • Steel measuring tapes—can include expansion correction.

12.6 Phase Changes

Outline with PSE Material to Use:

Start with a practical example to illustrate the principle (or even a visual table showing examples of phase transitions: water to water vapor, water to ice, etc.) of a phase change, then look at details, what is happening at an atomic level. For instance, as water boils, fast-moving atoms leave to the vapor phase, carrying energy away. The discuss phase transitions in some detail. Draw on and integrate two sections:

Pages 493-494: Phase changes

Pages 529-530: Phase change and heat of transformation. Do the example of calorimetry with phase change.

Also add bits on vapor pressure:

Page 448: Can use this example, extend.

Perhaps have vapor pressure diagram? Note meaning of relative humidity.

Finally, a brief note on how to change freezing/boiling points with pressure, dissolved substances.

Examples:

  • Kettle boiling water / how long to boil away?
  • Eat a frozen popsicle. How much energy to bring it to body temperature? Will this energy use cancel the calories? (Assess: does eating snow do you any good—as you need to use water to metabolize food?)
  • Conceptual example: cooking pasta; rapid or slow boil?
  • Conceptual example: why does spraying trees with water protect them from frost?
  • Calculation of dew point for certain amount of water vapor in air. (Could do 50% humidity at 60°F, what is dew point? Could do this as a passage problem if it doesn’t fit. Includes data, can relate to heat, pressure, etc.)

FSA/TIY:

  • Perspiring to keep cool. Losing heat via water vapor in breath.
  • Solid phase changes: white/grey tin, and historical examples where “tin pest” might have played a role: Napoleon’s buttons, Scott’s kerosene cans.
  • Frozen frogs: how some animals can be frozen without damage.
  • Why hot water pipes are more likely to freeze than cold.
  • Spray cans, how they work. (Could do as TIY: spray a can, note that it gets cold, discuss why.)

12.7 Heat Transfer

Outline with PSE Material to Use:

PSE does not explicitly treat these topics, so most of this section will be new. We can edit and reuse certain figures. This section will be largely qualitative.

Start with a visual table: examples of systems that transfer energy primarily by means of conduction, convection, radiation, phase changes.

Discuss, in turn, conduction, convection, radiation. Define thermal conductivity, give equation (Fourier’s law) and give a table of conductivities. Discuss convection in a qualitative sense.Give an overview of radiation, but save formal equation for the EM waves chapter (or even the quantum chapter, with blackbody radiation.) Simply note variables that determine efficiency of radiation as a transfer mode: temperature, area, color.

For conduction and convection, show atomic models of what is happening. We have nice figures from PSE that can be adapted for this, plus a very nice one for conduction that we didn’t use for Chapter 11.

Show how phase transitions can produce cooling/heating as well. (Most of the cooling that occurs when you blow over a cup of hot soup or coffee is due to evaporative cooling.)

Finish with threebrief sections stressing applications:

  • Keeping warm, keeping cool: strategies that animals use.
  • Keeping warm, keeping cool: for houses, buildings.
  • Greenhouse effect. The earth can only transfer heat by radiation; note how this works, consequences.

Examples:

  • R value for insulation / what do numbers mean?
  • Conceptual example: tile/carpet floors on feet, space shuttle tiles
  • Conceptual example: why put radiator (note inappropriate name!) under a window.
  • Conceptual example: why is it important to defrost your refrigerator?

FSA/TIY:

  • Themography
  • Keeping cool in space (radiation)
  • TIY: No frost under trees in the morning (for us in Colorado) or (for those of you in warmer climes) less dew. Why?

12.8 Diffusion

One could make an argument for leaving this section out, but since kinetic theory is done in this chapter we can treat diffusion pretty quickly, allowing us to treat the topic more efficiently than most books. It won’t add much bulk. (G/R/R does this is about a page and a half.) This topic represents a final chance to use atomic models to motivate understanding—and to show how the atomic nature of matter leads to macroscopic consequences. It makes a good bridge to the next chapter as well. Most books (though not all) do this topic, and it is one of great biological import—so we feel it should be in here.

If the chapter is getting too long, it could be dropped with minimal impact on the rest of the chapter.

PSE Material & Connections

PSE does not explicitly treat these topics, so most of this section will new. We can edit and reuse certain figures.

Start with examples of diffusion, including a picture and description of a system where diffusion is critical for mixing and transport.

Continue by discussing why diffusion occurs and what determines its rate by using kinetic theory ideas of Chapter 11 and the early part of this chapter. Rather than do Fick’s Law for diffusion (as C/J and Giancoli do) talk about distance traveled as G/R/R do—much more concrete:

Close with a discussion of why organisms of a certain size have to have circulatory systems, note that next chapter is about fluids. Something like “at the start of the chapter, we saw that elephants use blood for cooling... but also for transport of nutrients. All animals bigger than a certain size have circulatory systems. Next chapter we will look at fluids.”

Examples:

  • Diffusion of oxygen into capillary (like G/R/R)

FSA/TIY:

  • Drug delivery systems that use diffusion: patches, creams.

KJF Chapter 12,Matter, Heat and Temperature” Detailed Outline 23 Jan 2005