Program 21 - "Mechanical Heat"

Music(Sh, sh, sh, tick, tick, tick, tick... motor running.)MusicSilico: "We're back with Science 122, the Nature of PhysicalScience, the only telecourse that generates heat while it is boring.This is Program 21, Mechanical Heat."Before we're done with this program, we will have learnedabout the caloric fluid theory of heat as developedby Joseph Black along with his theory of specific heat.We'll examine the concept of heat as a form of energybefore studying the contributions of Count Rumford whose workset the stage for James Joule to establish amechanical equivalent of heat.We'll conclude with a consideration of our moderninterpretation of conservation of various forms of energy.

Here are the objectives for today's lesson.These objectives are also in the Study Guide at the beginning of the lesson.Before you begin to study the lesson, take a few minutesto read the objectives and the study questions for this lesson.Look for key words and ideas as you read.Use the Study Guide and follow it as you watch the program.Be sure to read these objectivesin the Study Guide and refer to them as you study the lesson.Focussing on the learning objectives will help youto study and understand the important concepts.Compare the objectives with the study questions for the lessonto be sure you have the concepts under control.That was a really nice voice.I never head that one before.Silico: "That was my Victoria voice.Did you really like it?"Yeah, but I don't know about the boring part.Silico: "It's a pun, you know.You taught me that earlier."I guess I remember.Puns, huh?Well, anyway.Hi, this is Program 21.We're talking about the mechanical equivalent of heat today.Much controversy revolved around the applicabilityof Newtonian mechanics outside of the paradigmof actual mechanics and ideal forces.People weren't really sure how much you could do with this paradigm.

Electricity hadn't been discovered yet,and it worked very well for astronomy.It worked very well for forces and things like that, but nobodyknew, for example, could you explain chemistry by mechanical forces.And if you can explain chemical reactions, what's the nature of the forces?And how can you measure these forces in the laboratory?And also, of course, the topic of today's lesson is, can heatand temperature be somehow incorporated into this paradigm?And, if so, how do you do it?How do you relate the idea of heat?Now, you may remember, that with the concept of nonconservativesystems like the pendulum that winds down, we have thequestion of where does the energy go?And it seems logical that the place to look for it is heat.So, let's look for a minute at the nature of heat.This had been debated from the beginning by the Greekphilosophers, and like many things in the Greek schools of thinking,there were two different schools, or two different areas of thought.One of those asked the question, "Is heat a substance?"In other words, like a fluid or, "Is it some sort of invisible chaoticmotion of some ultimate tiny particles of ordinary matter?"Now it's interesting, and we'll see this a little bit later on,that the Greeks talked themselves out of the existence of atoms.So they rejected the idea of the kinetic theoryor a theory of motion of particles being heat.These competing theories divided scientists all theway up until the mid-19th century.

One of these was the idea of a mechanical phenomenon,a Newtonian sort of thing, which we'll call kinetic theory,or the other was that of an imponderable fluid.You may remember the idea of an imponderable.This was called caloric theory.Newton had favored the vibration of what he called "corpuscles" of matter."Corpuscles" of matter, "corpuscles" just means small bodies of matter.The other opposing side had to do with the idea of a substancewhich had rather unusual properties for matter.In fact, you might saynon-Newtonian properties for matter.This substance called caloric which we'll look at in a littlebit more detail later on had unusual properties, for example,sometimes it had negative mass, and sometimes it has positive mass.But since you could really weigh it, it didn't makeany difference what kind of mass it had either.Chemists wanted to know how you could measure these forcesbetween atoms and how they related to heat.Because many chemical reactions give off heat when they take place.Just as an item of interest, in 1738, the French Academyof Sciences sponsored a prize essay contest on the nature of heat.All three winners, first, second and third placewere essays expounding the caloric theory of heat,the concept of heat as an imponderable substance.

Now this was interesting because we had seen theidea of imponderables had been disproven in physicsby Galileo and Newton's ideas of the space beingordinary matter, like matter on earth.This view was developed, the view of caloric was developedmathematically and proved useful in the explanation of manythermal phenomena even though it turned out to be wrong.Joseph Black's calorimetric scheme fitted the calorichypothesis and gave it added prestige, and we'llsee about that in a little bit longer.The kinetic interpretation, that is, the motionof "corpuscles" remained an open alternative,but the caloric theory was much more fullydeveloped and much more popular all the way upuntil the middle of the 19th century.

Now let's take a minute or two or maybe even three,to look at the caloric theory of heat.The caloric theory of heat is the fluid theory of heat.Now, I have to warn you ahead of time that this is an incorrect theory.And you might ask at this point, "Why are we studying incorrect theories?"I've had students in this class who would say,"Just tell us what we're supposed to know.Tell us the right stuff, don't tell us the wrong stuff."But, of course, we've seen from the model of geocentrism thatstudying the wrong theories helps us to understand how we get the right theories.Part of the reason we want to study caloric theory is that ourlanguage retains vestiges of this fluid concept.We talk about heat flow, for example.And we talk about objects soaking up heat.In some ways this leads to confusion.Because we speak of heat as a substance while we know rationally that it is not.And we're doing this metaphorically, but sometimeswe tend to confuse metaphor with reality.

Lavoisier, the French scientist, actually cameup with the term, caloric, in 1787, and the idea wasfirmly entrenched by 1790, but largely discredited by 1850.The premise of this was the idea of conservation of heat.And we'll come back and look at that idea of conservationof heat a little bit later on when we get into Joseph Black.But basically the idea is that when heat is transferred from oneobject to another the heat lost by one object exactly equals theobject, the heat gained by the other.This is true, by the way, even with our modern concept of heat.And this is the basis for calorimetry.So, the idea of heat, or the caloric theory, is that heat was thoughtof as a substance, a fluid, which could flow.In fact, the definition of a fluid is something which can flow.The fluid itself was called caloric.Don't confuse this with the word Calorie, just caloric.

So, let's look at what the properties of caloric weresupposed to be and then we'll get into some details about how it works.First of all, caloric was thought to be massless.That meant that it had no mass.And, of course, this is in direct contradiction to the Newtonianconcept of mass, and a substance having mass.Caloric could not be created or destroyed.And all substances contain caloric and can either absorb or release it.And heat, as we know, flows from hot to cold substances,so caloric was thought to flow from hot to cold substances.And this is sort of like counter balancing the attractive forcesof the particles of matter.It was generally accepted that matter consisted of smallparticles that were held together by some kinds of forces.The idea was that caloric somehow interfered with theseforces and that self-repulsion sort of caused it to flow from higher to lower pressure.You might think of this as sort of like the gas in a balloon.The caloric actually occupied space.So, gases, for example, had lots of caloric.The best way to really represent this would be,you know, like the juice surrounding the seedof a pomegranate, but I don't have a pomegranate.(Sweee, plunk.)Oh, well, there's a pomegranate.Let's take this to the ELMO and cut it up.OK, so when we look at the seeds of a pomegranate.I don't know how many have ever seen a pomegranateinside, but they're very juicy for one thing.Look at all that caloric fluid dripping out here.

You see how the seeds of the pomegranate are sort of surrounded by juice?And when I cut into it, the juice drips out.And you see how each little seed is like a little pocket of juice surrounded?Let me zoom in on one of those seeds so you can see how this looks like.Notice how each seed is sort of like wrappedin a little, in a container of juice.So, this is basically what the caloric fluid idea was like.That each of these particles of matter was surroundedby this caloric juice and when you cut into something or when youbored into something, it gave off heat as you know from friction,and so the idea was that when you add heat to something, the littlejuice pockets swelled up and caused the objectto expand very much like the heat of a balloon.Now let's turn our attention to the workof Joseph Black who lived from 1728 to 1799.

Joseph Black was a Scottish physician who was also a chemist and physicist.Silico: "Wait a minute.What do you mean by the heat of the balloon?"Did I say that?What I meant was the effect of heat on the balloon.The balloon will expand when it heats up.It's hard to say what comes out of my mouth sometimes.Anyway.Joseph Black became a professor of medicineat Glasgow and later became a professorof chemistry at the University of Edinburgh.He performed very early quantitative experimentsand was among the first to emphasize the importanceof such quantitative experiments to chemists.So he was actually a leader in the field, the emerging field of chemistry.And we'll get into that a little bit later on in a future program.Black discovered, for example, that carbondioxide is a gas thatis produced bothby respiration and the burning of charcoal and also by fermentation.And also it behaves like an acid when dissolved in waterand that it is probably found in the atmosphere.

Now we take all these things for granted today, but Black wasvery much ahead of his time in discovering these things.He also founded the theory of latent heat and investigatedthe content of specific heat, but was unable to really fit theminto place because of his belief in the phlogiston theory.Now phlogiston is another of these wrong theories that we'll studydown the road in a couple of programs.But Black was a very strong believer in the phlogiston theory of combustion.So his theories of specific heat and latent heat furnished abasis for Lavoisier's caloric theory which we'll also talk about a little bit later on.He also invented a form of an ice calorimeter whichwas a way of measuring the heat of objects.So, basically what he did was to perform quantitativeexperiments and emphasize their importance.Specifically he worked out the first satisfactorymethod for measuring heat.This was the calorimeter.Calorie meaning heat, meter meaning measure.The ice calorimeter was the first type, and later onhe invented the insulated water calorimeter.Probably one of Black's most important contributions was thefact that he noted that heat is conserved when it's transferred.And he also worked out the ideas of calorimetry and specific heat.So let's take a look now at the concept of calorimetry.

Calorimetry is nothing more than the measurement of heatand it uses the device called a calorimeter.Calorimeter is really a simple device and itassumes the conservation of heat.What that means is that it assumes that all of the heatlost by one object is gained by another object.It actually depends upon the change in temperature of agiven amount of a certain substance, usually water.So here you can see how this works.There's an inner cup which in this case holds a liquid.The liquid is water.We know that a certain amount of heat isrequired to change the temperature of water.The inner cup is insulated from the outer partof the calorimeter by an insulating ring so thatthe space in between is filled with air.There's also a lid on the top which prevents heat loss to the outside.A thermometer which measures the temperature of the waterand a stirring rod which stirs up the substance inside thecalorimeter, in this case, it's metal fragments.

Now the way this works is very simple.You take some hot metal fragments and of a knownweight, dump them and a known temperature, you dump theminto water of a known weight and a known temperature and yousimply measure the initial temperature and the finaltemperature of everything concerned.The idea is that the heat lost or gained depends upon the massand the specific heat of the substance and the temperature change.Remember now, this is conservation of heat.That the heat gained by one substance equals the heat lost by another substance.So, here's the relationship.The amount of heat is the mass of the substance multiplied by itsspecific heat, multiplied by its temperature change,and we usually represent the temperature changesimply with the "Delta T."So, if we look at the metal, we say it loses a certain amountof heat which is its mass times its specific heat, multipliedby its change in temperature, and the gain of heat of the wateris its mass times its specific heat times its temperature change.So I have a couple of real calorimeters here that we cantake a look at to see how they work.This is one just like in the diagram.It's got a lid on top.The other had a wooden lid, this has a plastic lid, and it's got aninner cup which is simply a small cup and an outer ring.The ring, again, insulates the inner cup from themetal of the outer cup as it sits inside.In Black's time this was the type of calorimeter he inventedbecause they hadn't invented styrofoam yet in Black's time.

In modern times we can simply use a styrofoam cupwith a styrofoam lid with a hole in it for the thermometer,which basically performs the same function.You'll notice that this one does not, is not made of metal.The silver on this calorimeter actually prevents radiated heattransfer which you don't get from the styrofoam cup,although it is possible to simply wrap the styrofoam cupin aluminum foil to prevent the heat loss.OK, with these calorimeters you can do all kinds of neat things.For example, you can do what's called heat of combustion.You can actually take something and put it inside the calorimeterand burn it to see how much energy it contains.You know when you talk about McDonald'shamburger having a certain number of Calories.The way to determine that is to actually put a pieceof the hamburger into a cup like this and seal it,and allow oxygen into it, a certain amount of oxygen and youmeasure the amount of heating of the water that goes onand transfer that into the number of Calories contained.You can do the same thing with chemical reactions.You can do the same thing with solutions in various kinds of things.So, all kinds of reactions, anything that gives off heat, the amountof heat can be measured in a calorimeter.

It was Black who came up with the concept of specific heat to begin with.And it was Black who actually clarified for us, for the firsttime, the distinction between heat and temperature.What Black did was to define and measure the specific heatof various substances to recognize the importance of the different substances.In trying to understand why different substances havethis ability to absorb different amountsof heat without changing temperature, Black cameup with what he called the water tank model.Now before we go into this anymore, keep in mind what specific heat is.It simply says that two objects of the same mass,if they're different substances, will absorband give off different amounts of heat whiletheir temperature changes by different amounts.So water has a high specific heat meaning it can absorb largeamounts of heat without changing its temperature much.And this is responsible for among other things the relatively mildclimate that we have here on earth where there's an ocean thatabsorbs and gives off heat, as opposed to the moon which doesn't have any.So, Black's water tank model goes something like this.That if you have two containers of different sizes,different shapes, if you pour water from one to the other,the level will change differently in differentcontainers, depending upon the size and shape.I think this is easier to explain if we see a picture of this.

In Black's water tank analogy you can imagine two different watertanks of the same height but different sizes.So here you have a rather large tank, here you have a rather small tank.So, suppose that you start with the level in tank "A" relatively high.So the starting level in tank "A" is here.The starting level in tank "B" is down here.The two tanks are connected by a stop cockwhich allows the flow of water to be controlled.So now you open the stop cock and what happens?Well, of course, what happens is that the waterlevel will fall in tank "A" as it rises in tank "B."I think you can see here that the amount of fall in tank "A" isgoing to be greater than the amount of rise in tank "B."So there are two things going on here, right?One is the level in the tanks before and after.The other is the amount of water that flows from tank "A" into tank "B."I think you can see here, can't you, that there's an analogy involved.The analogy is that the amount of water that flows from one tankto another represents the flow of heat.And I think you can also see that the amount of water lostfrom tank "A" equals the amount of water gained by tank "B" aslong as none drips out of the stop cock or is lost in any other way.At the same time, though, the level in tank "A" changesby a much greater amount simply because it has a smaller capacity.In this case it's a water capacity, but in Black'sanalogy we're talking about heat capacity.So, the level change represents the temperature.

So, here you have an object with a small capacity startingat a high level and falling a certain amount where you haveanother object with a large capacity absorbing allof the heat that's lost by the smaller object, or the onewith less capacity, where its level rises less.So, here's the "Delta T" or the temperature changefor the object with small specific heat, and over here is thetemperature gain for the object with large specific heat.And notice once again the level change is very much smallerin the object with the largest capacity.So, here, again, the analogy, heat is the temperature as the sizeof the tank is to the level on the tank.And heat is transferred from one tank or one object to another,and temperature represents the intensity of the heat.Again, here's the distinction between heat and temperature.We can think of temperature as a concentration or intensity of heat.And the level or the temperature depends upon the amounttransferred as well as the size of the reservoir.

Now it's time to look at the developmentof the concept of heat as a form of energy.Although Black's model of heat fluid becamethe popular model, heat as energy graduallydisplaced the caloric theory over a period of a hundred years or so.It's not hard to understand why this might happen because theconcept of heat, even as a fluid, shares certaincharacteristics with the ideas of energy.For one thing, heat like energy, appears when work is done.You can cause heat by rubbing your handstogether, or you can cause heat by any sort of friction.Heat also appears when mechanical energy disappears.For example, when you start a box moving across the floor,as it gradually loses its kinetic energy and comesto rest, the bottom of the box gets warm.

Friction causes heat.Heat, like other systems, also move naturally from high to low energy.We haven't really talked about this in this respect yet,but certainly, a ball as it rolls downhill is moving from a stateof high energy to a state of low energy.And a car, or any object that's moving, if you letit come to rest, it moves from a state of highkinetic energy to a state of low kinetic energy.So, you can say that both heat and energy movefrom a high state to a low state.And, of course, finally, the connection is that heat,like energy, is conserved during all types of interactions.And it's the conservation aspect that we really want to focus on.The next person to enter into the history of this idea of heat wasa very colorful character named Count Rumford.Rumford was actually named Benjamin Thompson and he wasactually an American who chose the wrong sideduring the American Revolution, became anex-patriot and found his way into Europeand became sort of the, what would you call him,I guess a courtier, a person who sort of hangsaround the court of kings and gets appointedto various positions and so forth.What Rumford really did was to show that calorichad no gravitational mass.In other words, that the substance could not existas a substance, if it was in Newtonian sense.

Now keep in mind, this was not a major breakthrough.Because people had already accepted the fact that it was imponderable.This was the fact that it had no mass was counteredby this Aristotlean argument that it wasn't ordinary matter,so why should it be affected by gravity.What Rumford did was really to weight hot and cold objectsand find that there was no difference in weight between them.People also came up with the idea that maybe caloric had a verysmall mass, so you simply couldn't measure it accurately enough.So, Rumford didn't really prove anything.What he did was start some interesting questions.There was, by the way, the precedent for this imponderable substance.And all the way through Aristotle's thinking,and we'll see later on that this pervaded evenafter Newton's time in the concept of chemistry.So, basically what Rumford did was to question the caloric theory.He did this based upon the concept of friction.And he really did it quite accidentally.He was put in charge of the boring of cannons.This is the boring cannon experiment.And what he noticed was that the men who were workingon this would put their teapots on the cannons to boil water.And that the cannons became really quite hot.He also noticed that heat was produced as long as the horses were working.

Now the theory at that time held that the caloric wascontained in the metal chips.Sort of like the juice of the pomegranate.And that the caloric was released when the metal was reduced to chips.But, Rumford wondered why it was the more heat was producedwhen the drill bit was dull, because the dull drill bit produced fewer chips.When the drill bit was sharp you would expect that it would cutthrough more caloric and release more heat,but in fact, it was just the opposite.So, Rumford also wondered how it is that this motionof the horses, continual motion, can create aninexhaustible supply of caloric.The caloric kept coming as long as the horses kept moving.

Now you would think that a substance like thecannon, no matter what kind of metal it was,would contain only a fine amount of caloric.It's again like the pomegranate.You can only squeeze so much juice out of a pomegranate,and if you tried to squeeze more than that out, you simply don't get it.But yet, the horses, working all day could produce thisinexhaustible amount of caloric.So, Rumford concluded that the heat produced was somehowdue to the motion of the horses, to the work done by the horses.Now this is a fairly obvious conclusion, because once again,you can create heat by rubbing your hands together and doing work.Rumford was not the first person to think about this.In fact, Francis Bacon, way back in 1620, had said,"Heat, itself, is motion and nothing else."And Boyle and Hooke expressed very similar thoughts.And Newton thought that "corpuscles" of matterin motion could explain temperature.Matter in motion, very Newtonian concept."Corpuscles" of matter...The problem was not in questioning the calorictheory so much, it's that no one was able to explainhow heat in the form of motion could be conserved.In other words, how heat could flow from oneobject to another without losing any of the heat.What Rumford did, among other things,was to produce a roughproportionbetween the quantity of work doneand the quantity heat produced.

Now keep in mind.If he was going to do this with the horses, he would haveto somehow measure the amount of work that was done by the horses.He would have to somehow measure the amountof heat that was generated at the cannon.And he would have to capture all of the heat that was made by the cannon.This is a difficult thing to do because the cannon is a largeobject, and some of it is inevitably going to leak into the air.So, his experiment, or his series of experiments actually werenot convincing enough to the caloric followers and althoughhe produced a qualitatively sound connectionbetween work and heat, it was quantitatively weak.And what was really needed, was some sort of way to actuallymeasure the amount of work done, look at the heat that wasgenerated by that work, and capture every last bit of the heat.In other words, what was really needed was to putthe cannon inside a big calorimeter.Or, to somehow shrink the system down to a smallersize so that everything could be finished.Before we go on to establish the mechanical equivalent of heat,we need to point out some of the common factors hereand sort of bring ourselves back on track.

So the idea is this.That Rumford had shown us that heat is produced aslong as mechanical processes continue,and not only that, but the amount of heat isproportional to the amount of mechanical energy dissipated.In other words, the more work the horses do, the more heat your produce.Now he hasn't got a qualitative, a quantitative relationship,but he certainly has a qualitative one.So, if we could find a quantitative relationship, in other words,if there is a quantitative proportionality, then we mightbe justified in assuming that mechanical energy and heatare different forms of the same thing.You see what we mean by this.If you can always say that a certain amount of heat isalways produced by doing a certain amount of work, and thatdoubling the amount of work doubles the amount of heat,that's the quantitative proportionality.Then we might say that they're different forms of the same thing.It's like saying if you always get two nickels for a dime,then the two nickels is a different form of the same thing.It's the different form of the money.So, Rumford had failed to establish this quantitative relationship convincingly.In fact, he didn't do it at all.But, Joule did, and we now establish today that the actualrelationship is what we call the mechanical equivalent of heat,which is simply the ratio of work done to heat produced.

Now this may not seem like such a major things, but what we'resaying here is simply that on one hand we look at work as amechanical process where we're looking at force times distance.And we define a joule as a unit which is accomplishedby a force of one Newton traveling over a distance of one meter.On the other hand, we establish the Calorie as the amountof heat necessary to raise a certain amount of water by a certain amount.In other words, one small Calorie is the amount of heat necessaryto raise the temperature of gram of water by one degree Celsius.So here we're saying that there's a correspondence between the two units.That a certain amount of work done will always raise thetemperature of water by a certain amount.Do you see the significance of this?Another one of them dedicated characters in our journeyof understanding the development of science is James Joule.Joule, as I said, is not only dedicated, he's a very interesting character.There's a little story to start off the story about Joule.The story goes that Joule had met the girl of his dreams, and was,in fact, on his honeymoon in the Swiss Alps at a resort verysimilar to what Americans might go to Niagara Falls.He was walking along this garden path with his new bride on theirwedding night and saw a waterfall.And the waterfall keyed a question in his mind.He was familiar with the concepts of workand energy--Newtonian concepts.And he got the thought that if the water is losing potential energyas it falls over the waterfall, that by the time it reaches thebottom, it should have gained kinetic energy and he thoughtthat when the water hits the pool at the bottom it should give upthat kinetic energy and what would it be transformed to but heat.It occurred to him that the water ought to be warmerat the bottom of the waterfall than at the top.The story goes that he abandoned his bride and proceededto climb to the top of the waterfall to measure the watertemperature and then climbed to the bottomof the waterfall to measure the temperature,and did this for three days, consuming most of the honeymoon.

Now I do want to report that they did produce a few children soeverything must have worked out OK.But I don't imagine the bride was happy about this.His attempt to measure the temperature differenceat the top and bottom of the waterfall failed miserably.But, he saw this as a potential to understand this relationshipbetween work and heat, and it occurred to him thatif you could somehow capture the heat that wascreated by this loss of energy, that you couldcome up with a mechanical equivalent which he eventually did.There's more to the story.Among other things, Joule invented accurate and reliablethermometers and repeated this experiment many times,hoping that if he could have a more reliable and accuratethermometer, he'd be able to detect temperature difference.What he failed to understand, of course, was whatever heat wasgenerated was immediately lost to the environment, to the atmosphere.And I think he did understand this later because he built a systemwhich he used then to isolate the heat in a calorimeter very muchthe same way that Black had done in definingcalorimetry in the first place.

Joule also had, brought other things into this.For example, he saw the potential of the newly invented electric motor.The electric motor had been invented in actually 1810 or in the 18 teens.And Joule hoped to replace steam powerwith electric power in his family brewery.His family owned a brewery in England; made beer.So he had hoped that he could replace expensive steam power.By this time the industrial revolution was alreadydepleting the coal supplies in England and coal was becoming very expensive.So he hoped that he could use battery power to power the electric motor.The battery, by the way, was discovered in 1800, ten yearsbefore the electric motor, to power the machinery in the brewery.It turned out that the cost of the zinc that was consumedin the batteries was much greater than the cost of the coal.But it was still a good thought.So, what Joule actually did was to come up with many differentexperiments where he tested the relationships of this heatand energy thing in every conceivable situation.He did measure the heat by calorimetry.He did all kinds of different things.He measured the heat developed by electric currentfrom the chemical reactions that were taking place in batteries.And I mentioned earlier, the battery was discovered in the early 1800s.I think I said 1800, but it was actually 1803.He was able to measure in a calorimeter the amount of heatgenerated by an electrical current flowing through a wire.He also measured the heat from electrical currentproduced by an electrical generator.So, with a generator, you can turn the crank, and you can turnkinetic energy into electrical energyand then you can then turn electrical energyinto heat energy and you can measure the amount of heat produced.

Now, of course, the source of the generator current,from the electric generator is the mechanical work that it takes to turn it.He also stated what's now known as Joule's law.Which simply says that the heating produced by anelectric current is proportional to the square of the amount of current.Now we haven't studied much in the way of electric current yet,but we'll do that in a later lesson.But the idea that if you doubled the current, you quadrupled theheating effect, is responsible for much of our heating equipmentlike stoves and heaters and that sort of thing that uses electrical heat.Joule also did lots of studies by studying the amount of heatproduced by friction between moving cast iron plates.So he'd take two big plates of cast iron and he'd grind them together like this.Very much like rubbing your hands together to produce frictionalheat, and try to capture all the heat.

Now you can imagine the size of the calorimeter that it took to do this.It turns out that the thing that really brought Joule into theforefront or really crystallized his idea of conservationof energy was the fact that he designed a calorimeter in whichhe could use various liquids which were heated by rotating paddles.Here we have a picture of Joule's churn or Joule's calorimeter.And basically it was modeled after Black's calorimeter.It was simply an insulated container, the insulation hereis indicated by the stippled pattern that had baffles in it.It had baffles to increase the surface area so thatthe water would drag as much as possible.He had a churn, these are paddles that could be turned by a spool.The spool had thread on it.It was connected to a pulley and hanging over the pulley was a weight.So that as the weight fell, it turned the spindle whichturned the paddles which generated friction inside and generated heat.

Now he was able to do this because notice out here wherethe weight is, in a Newtonian concept work is force times distance.So by raising the weight, letting it fall a certain distance, he couldmeasure the amount of work done by the weight.Since he was capturing all of the heat inside the calorimetersince there was no heat loss, then he could assume that allof the work that was done went into heating the waterand he could also do this repeatedly.So he could do this as many times as he needed towith the assumption that not much heat was lost.I should also point out that the thermometer that Joule usedwas one which he invented himself which was accurate down to oneone hundredth of a degree Celsius.It was the most accurate thermometer in his time.What he did then was simply to do this time after time, after time,measuring the amount of work done, measuring the increasein the temperature, and, of course, by knowing the massof the water, and the temperature increase, he could calculatethe amount of heat that had been transferred to the water.He also tried this with various other liquids.He tried this through oil, with oils, he tried it with alcohol,he tried it with mixtures of various things, and I shouldpoint out that the total experiments that Jouledid consumed 40 years of his life.Before he was able to actually come up with a statementin which he could determine the quantitative relationshipbetween work and heat, that we called before, the mechanical equivalent.

So Joule determined the quantitative relationshipbetween work and heat that we called the mechanical equivalent of heat.That is one calorie is 4.18 joules.So what that really means is that joules and Calories are simplydifferent units for the same quantity in the same way theinches and centimeters are the same units for different, different units for the same quantity.Input done in work, in joules, appears as heat and calories.This is enough in itself, but probably even more importantthan this is that it also now allows us to include other typesof energy other than mechanical energy into our equation.For example, it helps us to understand where theenergy goes in the pendulum.And we can convert now that energy directlyinto heat even if we can't measure the heat.So, what Joule allowed us to do was to add heat,electrical energy, and chemical energy to ourwork energy theorem or our work energy equation.

The idea here is that energy exists in many different forms,and these forms are all interconvertible one to the other.So, the different forms.We already talked about mechanical energy.This includes potential energy and kinetic energy.But now we can add here electrical energy.We can add chemical energy.We can add radiant energy.We can also add thermal energy.And all of these different forms of energy are interconvertible backand forth and it's also, of course, that you can convert backand forth between the various types across the pentagon here as well.I didn't include nuclear energy here because we won't talkabout that for a while, and I didn't want to confuse you anymore than necessary.But, we can use this now to see a good example of how thisconservation of energy works in a modern sense.That is with the generation of electric power.Here's a picture of the Glen Canyon Dam.This is a dam across the Colorado Riverin Southern Utah that's used to generate electric power.So the question is, "Where does that power really come from,where does that electrical energy really come from?"And what happens is very simple.

The original source of energy is energy from the sun.That's thermal energy.Actually, it's radiant energy.It strikes the earth's surface, becomes thermal energy.That evaporates water and lifts it high into the atmosphere.This increases the potential energy of the water.And, of course, condensation releaseslatent heat into the atmosphere when clouds form.Eventually precipitation collects in streams and flows downhilland because the water then has potential energy which ittransfers into kinetic energy as it flows down the hill,and some of this, of course, is used for erosion and for friction.So, we dam the stream then trapping the water at a higher level.

So now we have a difference in water levelbetween the top of the dam and the bottom of the dam.The potential energy now that's stored in the waterat this height is changed to kinetic energy asyou let the water flow through the pipe.That kinetic energy is transferred to a turbine.By doing work on the turbine exerting forces on it,turning the turbine, the turbine then is, converts the motionof the turbine into electrical energy by means of a generator,and then the electrical energy is transmitted through the wiresas both electrical current and magnetic field.And, of course, this eventually appears in the plugs in yourwall and the final use of that energy depends upon the typeof transformation at the user end.In other words whether you turn it into heat or whether your turnit into motion with an electric motor.Whether you turn it into light, whether you turn it into someorganized form of energy like a television or a radio.But in any case, the original energy has comefrom the nuclear reactions in the sun, transmittedthrough space all the way down the chain.Each time converting energy from one form into another.So now let's take a look at some examples of thesetypes of energy conversions.

The first thing I want to look at is the conversion of thermalenergy into mechanical energy by the use of an engine.This is actually the same thing that you saw earlierin the program, it's the heat engine.I'm going to fire this thing up really quickly just so we cansee how this works, and, well, we'll move the fire around.I think I'd better move you out of the way.Don't panic now, this is only moving you.I'm not going to shut you down or anything.That's good.OK, so I'm going to fire this thing up.I want to point out here that at the same time that we're doingthis, we're also demonstrating the use of the conversion of thermalenergy into light energy, because the fire does have a certain amount of light.This engine operates entirely on heat, and you'll notice that onceI start to heat this, nothing much happens until I givethe engine a little bit of a kick.And once I give it a little kick it takes off and runs by itself.

Now you might ask, why we don't use an engine like thiswhich requires no external fuel other than the heat.Why don't we use it in cars and things?The reason is that it's not very efficient in terms of having power.But you notice that it does run relatively fast.I think I might have just broken the engine.There we go.OK, so I want to shut this down.You notice that as soon as the heat goes away, the engine itselfwill eventually shut down as the heat reservoir here begins to cool off.I don't know how long it takes to run down, probably not too long.Seems to be running an awful long time today.There it goes.So you notice that it does require a fairly significant amountof heat to get it running, and as I said before, it's not really very efficient.So that was the conversion of thermal energy into mechanicalenergy with the use of an engine.

Now let's take a look at transforming mechanical energyinto electrical energy with the use of a generator.Now I actually have a generator here somewhere.Let's see.There it is.Oh, this thing weighs a lot.Ah.This is an old generator, older than even I am.So, what we have in here, I don't want to get into the detailsof the internal workings of this, but basically it's anelectromechanical thing that has coils of wires and magnets.And see, if I turn this, the light bulb begins to glow.In fact, the faster I turn it, the brighter the light bulb glows.So, what I want to do now is to show you that the electricalnature of this, hook up this electric meter and,hopefully, the meter will actually work.Of course, things like this always work because they're electrical.And let's see if it actually works.Let's check and see if it works.OK, there we go.So, you'll notice now that as I turn the crank, the needle on the meter rises.And the faster I turn the crank, the higher the needle goes.

Now the interesting thing to note here is that even if the lightbulb is taken out of the circuit, the light bulb doesn't glow,but the meter still shows electricity is flowing.So here we're taking mechanical energy, that is the kineticenergy of motion, the work actually being done by my handand turning it into electrical energy which either lightsthe light bulb, or drives the meter.So that was changing mechanical energy into electricalenergy through the use of a generator.Now we want to change chemical energy into electricalenergy through the use of a battery.A battery is really a simple device and I want to make one here for you.I've got to get rid of the generator, everything first.I'll leave the meter out there because I'll need that.Put that back here.OK.So here's a very low tech battery.This is just a container.I've got a couple of pieces of metal.I've got a copper strip and a zinc strip.We're going to make a bimetal battery.So what I want to do is to put these things in here, like this.And attach the meter to them and see if there's any sort of a reading.There shouldn't be.The way this meter's been working, who knows.OK, here we go.OK, so now, I want to add some water to this and see if anything happens.The meter might move a little bit.

Now the water simply acts as a carrier for the electricity.And the chemical reaction goes on between the zinc and the copper.If there's not much of a current, I can add a little bit of electrolyte.In this case it's a little bit of hydrochloric acid.You can try this at home.The hydrochloric acid is not necessary.You can use vinegar, or, in fact, even salt water should work.And now if I shake this around a little bit and mix it,you should see the needle move on the meter.If the needle doesn't move...There it goes!You see that it's generating a little bit of electriccurrent, generating a voltage.

Now what's going on here really is that there's a chemicalreaction going on between the copper and the zinc.It doesn't have to be copper and zinc.In fact, it can be copper and other metals as well.Although the voltage you'll get are different.Here, for example, is a piece of aluminum.If I connect this up to the aluminum.Whoops, dragging the meter around.If I connect this to the aluminum, you'll see that there's still alittle bit of a voltage generated but not nearly as much.Now, there should also be a reaction between the aluminum and the copper.Oops, that's a negative.You notice that the...which one is positive and which one isnegative, depends upon which two metals you have hooked up.So there's a reaction between the copper and the aluminum.Your common dry cell battery, not alkalinebatteries, are actually made out of zinc and carbon.And I have a carbon rod here.Carbon's not a metal, but there's still a reactionbetween the zinc and the carbon.So if I connect this up to the zinc;connect this one up to the carbon.We should still see a reaction.We should still see a voltage.Oops, I got the negatives and positives crossed again.Let's do this.And hook this one up over here.And there should be a voltage now between the zinc and the carbon.You can't read what it says on the meter, but it's about a voltand a half which is your typical dry cell battery.

Now, just in case you might think that there's something specialabout the water here, I want to point out to you that it really isn't.I want to make sure that the copper and the zinc still register a voltage here.Isn't this fun?If you have a meter, a volt meter at home, you can try this.OK.Move things around like this.So, there's the current between the copper and the zinc.What I want to do not is to show you that if I take these outof the solution, the current immediately drops;immediately drops back down.So what I want to do is to get rid of these things.I'm going to empty the water out of here, and try the whole thing again.But just to show you that the water isn't really the keyelement, I'm going to try it with a different substance.Put these back in here.You notice that again there's no reading on the meter.So, instead of water this time.(Gulp.)I hate to waste this good orange juice.And there should be a reading on the meter.And, of course, like so many things that we try to do here.Here it is.Notice that the orange juice still provides the necessary acidto provide the electrolyte the movement of ions whichwe'll study in a future program to cause electricity to work.You can also do this.You may have seen these at some point or another, little clockpotatoes where you plug in the thing to a potato.It's got two little spikes and you plug them intoa potato and it runs a digital clock.So, again, it's the bimetal aspect here, the two metals togetherwhich cause the battery to operate.In a future program we'll talk a little bit about the inventionof the battery and how it works in somewhat more detail.But here we are converting chemical energy, the energyalready stored in the metals, into electrical energy simplyby the use of, in this case, orange juice.So that was changing chemical energyinto electrical energy with the device we call the battery.

Now we want to have some fun with changingchemical energy into radiant energy.The process is called chemiluminescence,which simply means light from chemicals.So let me move this stuff off of the tabletop.There must be some place to put this, yeah, I'll put it down there.So what I've got here is a light stick and you probably seenthese things if you've been to concerts.It doesn't seem to glow very much.Maybe we could have the lights down.May we have the lights down, please.There we go.Ah, there it is.Now you can see the glowing stick.Really this is just a chemical reaction that's very similarto the reaction of, that fireflies and glow worms use.For years people wondered how to get light out of chemistry this way.This works from a chemical reaction.I have another stick here which I'll do this for you in the dark.Can I leave it down there.You still see it?And all you do with these things is to break them.Notice as I break it how it begins to glow.Right.And, all I'm doing here is mixing these, allowing these chemicalsinside the tube to mix, to form a mixture which lights up.Isn't that great!Notice that they come in different colors?Put that one down there, and here's another one.This one the blue light.

Now again, this is simply the, a combination of chemicals.And the neat thing about this is that it's light without heat.Normally, you know, an iridescent bulb, or even a fluorescent bulbgives off a significant amount of heat.And these things are entirely cold.That is, they give off no heat whatsoever.The chemical formula here is an organic chemical, but it's madein such a way that when the two chemicals combine,it gives off this nice lighted color.There.What do you think of that?Is that cool?OK, may we have the lights back, please.This chemiluminescence is actually a, it's mimickingan organic process that used, that firefliesand other kinds of animals use.Of course, we know that the process works backwards as well.It's possible to turn radiant energy into chemical energy.This is done all the time.In fact, it's our major source of food.It's the process of photosynthesis.That is when sunlight translates into chemical energy throughthe process of photosynthesis in plants.I don't know where that thing went.I guess it just disappeared.Hey, that's really neat, how did they do that?So, one last aspect of conservation of energy hasto do with an Englishman named Julius Mayer.

Mayer was actually a physician who did workin the South Seas as well as in England.Let's bring my little friend back over here.Just, there we go, just to get things set up again.Mayer was, again, a physician.He was fascinated by the suggestion of Lavoisier who wasa chemist, who we will study later, that animal heat; that is,the heat of metabolism, is generated by a regulated form of combustion.Here is what Mayer did.He was working in the tropics and he noted that blood in the veinsof people in the tropics is redder than those in cold climates.Now this is another one of these examples of how the creativemind can put things together when no pattern apparently exists.What has this got to do with conservation of energy?Well, what Mayer did was to relate the heat of metabolismto the heat loss and the work performed by the body.He simply recognized that in cold climates people have to use more oxygen from their blood.In other words, they had to generate more heat in orderto compensate for the loss of heat from the cold.So what he did basically was to recognize that the conservationof energy involved here was the chemical energy of food beingturned into metabolic heat and metabolic heat, then, wasregulated through the body thermostat.

It's interesting that both Joule and Mayer sort of claimed creditfor this conservation of energy, and they both get recognitionafter a long battle in the scientific literature over the priority.Such battles are common in the history of science.Other examples are Newton and Leibnitz fightingover who invented the calculus.There are others who will come up as we gothrough our history of science in our long voyage here.As it turns out, Joule get's the energy unit named after him and Mayer doesn't.We find ourselves at the end of another program.In this lesson we've studied the contributions of Joseph Black,Count Rumford, and James Joule to the idea of heat as a form of energy.We saw how caloric theory became transformed into an energy theory of heat.But, the question still remains as to how this concept of heat asa form of energy fits into the Newtonian paradigm.We'll explore that in future programs as we move down the river of scientific heritage.

We also learned that there are many different formsof energy, not just mechanical energy.Mechanical energy is one, but there's also chemical energyand thermal energy and electrical energy and radiant energy,and even nuclear energy, which we didn't really consider in detail.We learned that energy can be transformed backand forth between the various types.And, in fact, much of our modern technology involves these kindsof transformations and is devoted to figuring out new waysto transform energy from one form to the other.We also saw a new statement of conservation of energy whichsays the amount of energy in a closed system remains constant.This means, basically, that energy can be neither created nor destroyed.It's simply transformed from one form to another.This basically means that in the universe at large,the total amount of energy remains constant.This is an interesting concept that we'll comeback to on in our last program.

So, I also want to mention the idea of energyconservation versus conservation of energy.We heard the term, energy conservation, to mean thatwe're supposed to conserve energy, meaning that we'resupposed to use no more energy than we really have to.This is not to be confused with our concept of energy conservationwhich simply, again, says that energy can be transformedfrom one form to another, but the total amountremains constant during these transformations.Well, I think that's about it.So, what else do I have to say?Remember, when it comes to science, get physical.Anything to add to that, my silicon friend?Silico: "I like the chemiluminescence part thebest, but I thought energy conservation meant that we should use less energy.Do computers use less electricity in the topics?"No, that's because you don't have homeostasis.Well, anyway, I'm going to play with my stuff.Bye.Music