I dont know what to say but im just too busy. Im just too busy with my work. And he say over the phone, oh, thats too bad because im into giving massages and i have to do a onehour continuous massage. Massage . Well, maybe i can find the time. Come on over, right . So they come over and they gave you massage and they pour some alcohol on your back. And when they pour the alcohol on your back, you, oh, wow, its cold. He say, no, its not cold. I got it from the medicine cabinet right where all the other stuff is. Is that alcohol colder than anything else in the room . No. No. If it were, what would happen . Thermal equilibrium. The other things would heat it up. Isnt that true . Doesnt heat flow from high to low temperature . And arent all the things in our environment here, arent this, this, this, all these things the same temperature . What if this book were hotter . What would it do to the table . Energy would cascade from the book to the table until they both became the same temperature and they will level off. So that alcohol thats poured on your back has the same temperature as anything else around, but it feels cold. And why does it feel cold, gang . Because what is that alcohol doing . What its doing is what were gonna be talking about today. Its changing state. Its changing from the liquid state to the gaseous state, okay . And we call that what . Begin with ev . Evaporation. Evaporation, thats right. And were gonna be learning that evaporation is a cooling process. You know, sometimes youre swimming and you come out and youre all wet, a little breeze come by and you feel kinda chilly. But if no breeze comes by, you dont feel so chilly. And whats going on . When that breeze comes by, what happens to the water on your body . Evaporates. It evaporates. When it evaporates, how does your body feel . Begin with a c. Cool. Cool. Now, were gonna ask the question hc. Why is it that evaporation is a cooling process . And we can reason that out if we think small. See this glass of water here . Do you think all the water molecules in that glass are moving at the same speed all the time . How many say, oh, yes. At exactly the same speed all the time. Stand up. Nobody. How many say, well, theres a whole distribution of speeds and the average that relates to that which we call temperature . Show of hands. Yay, we got the idea. But you have all kinds of speeds in there, gang. Youve got fast ones, youve got slow ones. Youve got some at absolute zero in a moment [makes sound] when it comes to a dead halt, boom, that corresponds to absolute zero. The next minute, something hits it, bam, bam, bam. Theyre moving in all kinds of speeds. So you got a distribution of speeds. And the distribution goes Something Like this. Its like the distribution of our test scores. Remember how your test scores were . Score, numberno. Here was the score here and the number of people getting the score . Well, the same type of thing here. This would be the temperature or we could say the motion or the Kinetic Energy. The Kinetic Energy of molecules in a glass of water versus the number of molecules. And whats the graph just say . That down here, theres a few that are going slow and theres a few that are going fast. These are relatives ideas here, huh, relative values. And most are going right about here in the middle. And when you talk about the temperature of the water, youre talking about the average Kinetic Energy, what most of these things are doing. Isnt that true . Now, which of those molecules do you think, in the glass of water, would be most apt to evaporate, the fast ones or the slow ones . Fast. Fast. I remember when i was a little kid, my father would drink his coffee and it would be too hot to drink, hes gotta go to work quickly. And what hed do is hed take the coffee and then pour it on a saucer. Hed lift up the saucer and drink from that. It used to get my mother annoyed. She says it wasnt proper. What do you mean proper . He was using physics. Why did he pour it on a saucer to cool it, gang . Oh, you dont be knowing . Well, it turns out evaporation is guess what kind of phenomenon . Surface. Surface area. The more surface, the more evaporation takes place. If i take a glass of water and set it here, itd take a long time for you to see the level go down. If i take that glass of water and spread it over the top of the table to increase the surface, by the end of this lecture, that water will be . Begin with a g. Gone. Gone, okay. It would evaporate because thered be more surface. All my father did was increase the surface area. And when he increased the surface area, he gave what kind of molecules the chance to get out . Fast or slow . Fast. Fast. Fast ones leave. And when the fast ones go out into the vapor state, whats left behind . Relatively slow. And so your most energetic molecules are gonna leave and thats gonna push the peak down cause the slow ones wont have the fast ones to bump into anymore. And its not like there are some that are always slow and some that are always fast. These are all water molecules, the same mass. So the slowest at one moment might be the fastest at the next moment. Theres a continual chaos of motions in there and its always completely random, random that peaks out at some particular average. And when you take the faster moving and have them escape to the air, it stands to reason the slower moving are left behind. So thinking small, we can see why evaporation is a cooling process. This is one of the things that makes sense, yeah . Any questions in this . I saw a nice example of this when i was in india some years ago. I was in khajuraho, india. It was really hot, like 110 fahrenheit. And i was trudging through and all of these people are out in a field. And theyre all doing work out there, working in the field. In a corner of the field was a kid, a young kid. He must have been eight years old or so. And that kids job was to continually keep a great, big clay pot of water cold. And how he did that is he had a gunny sack over the pot. The pot was open like this. He had a gunny sack over like burlap, yeah . And he had a little pot down here and a long stick with a gourd in there. And he would just keep making sure that the gunny sack stayed wet. And as long as he kept the gunny sack wet on that hot day, honeys, the water inside was begin with a c and i aint saying cool. Cold. Cold. Hc. Be checking your neighbor. You see how that works, gang . You see how that works . That gunny sack, water is evaporating, right . Which water molecules are evaporating, the fast or the slow . Fast. Fast. The fast. Whats that leave behind . Slow. Slow. So the gunny sack then gets a little cooler than the outside. But the gunny sack is against the clay and the gunny sacks are a little cooler than the clay. Which way does energy go, from the clay pot to the gunny sack or the other way around . Clay from the clay pot to the gunny sack. Heat flows from High Temperature to low of itself, yeah. And so, what happens to the gunny sack i mean, the pot gives its energy to the gunny sack and that keeps going off, off, off. You see what im saying . And so, the pot gets cool, cool, cool, but the pots against the water inside. Now, if the pots cooler than the water, and the pots against the water, which way is the energy flow gonna go, gang . From the water to the from the water to the pot. And so you see, so long that he keeps having the fast moving molecules leave on the outside, hes cooling the water on the inside. Thats beautiful physics. Let me ask you a related question. Why do hot dogs pant . Seen a hot dog [pants] go like that all time. All time, get the tongue out. Why . Do you know hot dogs pant . The answers simple, no sweat. Dogs dont sweat. The only place dogs sweat are in between the toes. But intheir body, they dont sweat, so they have to evaporate to cool. Where do they do that . Right inside where it counts, right down to the bronchial tract. [pants] theyre evaporating from the tongue and the mouth and right down through there. So theyre getting a nice, nice cooling. And on really hot days, why do you see a dog goin [pants] like that, okay . Maybe trying to get the wind going through here. Im kidding about that. [laughter] why do the pigs roll over the mud . Because theyre dirty creatures. Come on, come on, why . They dont sweat. They wanna again, no sweat, see . And they wanna keep they wanna get wet. And how do they get wet . Get wet wherever they can. And they get wet and when the breeze come by, evaporation. Evaporation does what to them . Begin with a c. Cools. It cools them. Hey, hey. Natures thermostat. Us, when you overwork, you guys start to sweat. Can i say sweat . All right, perspire. We startits a little more refined, right . We perspire. Now, why do we perspire . Natures thermostat. Isnt that true . Natures thermostat. The harder you work, the more you tend to overheat, the more you sweat. And the more you sweat, the more you cool. Cool. Begin with ev. Evaporate. Evaporate and release the the perspiration in your body evaporates, yeah . And when that evaporation takes place, whats that do to the skin, cool it or warm it . Cool it. Cool it. And so you feel cooler. Aint that neat . Ill tell you where that short circuits out. Do you ever stay in a hot tub too long . Yeah, its bad. I remember way back in the seventies when i it used to be common back then in San Francisco in the seventies to go hot tubbing. You guys, when you meet someone new, you go to a movie or something, right . [laughter] i remember one time, this lady, i asked her out, asked her to go to a movie. Says, why dont we just get to know each other better . Why dont we go to the Grand Central hot tubs . [laughter] i dont know her yet, you know . I have thismy fondest dreams went a little bit too fast. Can i handle this . You know . Its a true story, by the way. And soyeah, we went to the hot tub. Hey, and in the hot tubs, all my students were there. Hey, what are you doing here . Hey, mister hewitt, what are you doing here . [laughter] hey, hewitt. Hey, that checkyourneighbor routine worked, didnt it . Hey, all right. But, anyway, i got in the hot tub there, and its really, really hot, yeah . And im in there, and shes outside, and she says, come on here, letscome over here, ill give you a rub down. Oh, ill just stay in the water here a little longer. [laughter] that waters hot. And that water is hot, and guess what im doing inside that tub. Sweating. Sweating like mad. Oh, yes. But the sweating, usually, it corresponds to begin with ev. Evaporation. Evaporation. And evaporation, usually cools. Cools you. But im in the water. And whats happening there, gang . Any cooling going on . No. So what does the old thermostat up here say . M s, m s, m s. More sweat. More sweat, more sweat, more sweat. So im under the water sweating, sweating, sweating profusely. My heartboom, boom, boom, boom, boom, boomoverworking. I interrupted my bodys natural function by getting in that hot water and preventing the evaporation doing the cooling. And, honey, if you wanna get wasted, talk about limp city, you will really get wasted if you stay in the hot tub too long. And you think sometime, people thinking, oh, you come out, hey, hey, man, hey. No, its not that way. You come out [makes sound] [laughter] youre all wasted. Youre all drained out. If youi wonder, too, about these deodorants, you know . You put these deodorants on that make it so you dont perspire . Can those be good for you . That mean youre gonna overheat. If you prevent natures function, sweating, youre gonna overheat. And if you overheat, your heart overworks, and, honey, you get wasted, not energized. Just the other way around. Kinda makes sense, huh . Hey, if evaporation is a cooling process, how about boiling . Oh, no, boiling wouldnt be a cooling process. Boiling is a heating process. Oh, no, no, no, boiling is a cooling process. Dont believe it . You come home sometime, your hands are all hot and sticky, you wanna cool them off. Your moms over there cooking a great big pot of boiling water ready to put some spaghetti in. You read in the book, boiling is a cooling process. What do you do . You take your hot and sticky hands and you dunk them into boiling water. You mother says, what are you doing . Im cooling them off. Good idea or bad idea . Bad. Bad idea. So is boiling really a cooling process . End with a p. Yup. Begin with a y. Yup. Yup. Yet the question is begged, whats heating and whats cooling. Yes. Tell your friends that when youre cooking some tea and youre boiling some water, and they come by, say, what are you doing . Oh, im cooling off the water. Theyll say, youre what . I say im cooling off the water. And they look at it and see all the bubbles coming out. Youre cooling the water . Say, yeah, im cooling the water. Put your hand above. Ooh, i burned myself. You know why you burned yourself . You say, because heat came from the water. Thats what i mean by cooling. See, i got the fire underneath, thats heating the water. Thats the part thats heating the water. But the boiling process does what . Cools the water. Honey, the boiling takes away all the energy. To say you take energy from something is to say you cool it. If redhot lava is coming down the mountain and it cools, does that mean its cold . No, but its cooling as its coming down. And your boiling water is cooling as it boils. Isnt that neat . Thats why i use a Pressure Cooker. Use a Pressure Cooker to prevent the boiling. That will prevent the cooling, and that will allow you to get more heat, more internal energy in your water and cook your food faster. Thats what its all about. Because more pressure lets look at that. Heres regular boiling. Lets not look at Pressure Cooker yet. I wont put the lid on, okay . This is just regular boiling. Lets use whats the temperature at which water boils, gang . 100 degree celsius. Is it 100 degree celsius . Is that right . Lets suppose we get to 98 degrees celsius. Now the water molecule in there, theyre going a lot faster than they were at 78 or like that. Isnt that true . Okay, now, theyre 98. Now, those water molecules are all banging around in there. A little group of them says, hey, gang, lets cut out, lets form a little bubble. Lets be buoyed to the top, and lets cut out. Lets steam it out right now. And so what they do is they form a little bubble here. And you know what happens when they form that little bubble . 30 kilometers of air, honey. 30 kilometers of air are squashing down. Squash right down and smash that bubble right back into smithereens. The air pressure outside is simply too intense to allow that bubble to form. Those molecules are gonna theyll have to go faster than that to exert enough pressure to overcome the pressure, mainly, of the atmosphere, let alone this height right here. So thats what happens. So the water then, since its not cooling, the water goes up to 99. And the water molecules say, hey, lets try it again, gang. They cut out like this. And what happens . Old atmosphere up above says, no, you dont. Smash. Smash them right back down. What happens . No cooling, the water heats up more. Now, the molecules are more energetic, right . Will exert more pressure when they form a bubble, yeah . Now, they form a bubble. Atmospheric pressure up above says, oh, no, you dont. Smash. All the bubble says, oh, yes, we do. Squash. Because, now, the bubbles are pushing out with a muchas much enough pressure to overcome the atmospheric pressure plus the pressure of the water. And thats the temperature in which boiling takes place at sea level. Now, you go up in the mountains where youre closer to the top of the air. Does the atmospheric pressure pushes hard . No. No. So boiling should take place at a higher temperature or lower temperature . Lower. Does it make sense, a lower temperature . Isnt that neat how physics makes sense like this . See . And if you keep taking the pressure away, pressure away, pressure away, youll get boiling at Room Temperature and below. Theres a wonderful, wonderful experiment at the exploratorium in San Francisco. Its my favorite. And all it is, is theres a cylinder, a plexiglass so you can see inside, and a vacuum pump. And you squirt a little water in a little cup. And you put the water in the cup at room water temperature, you can even put your hand in there and everything, and you close the thing. You throw the switch. Stretch it. Take the air out. It starts to lower the pressure. And guess what the little water in the cup starts to do, gang. Boil. Begin with a b. Boil. Boil. And people walking by dont know whats going on, and they see the boiling water. And they ask questions like, gee, how are they heating it up . Theyre not heating it up. But its boiling. The only time you ever see boiling with someone heating it up, honey. But theres boiling when you dont heat it up too. Theres two things that go on with boiling. What are they . The heat you give and the pressure you exert. And if you change either one, youre gonna change the temperature which youre gonna change the temperature of the water. Yeah . And so what happens is its boiling, boiling, boiling. Now, heres a neat thing. It continues to boil. The pressure goes down, down, down. And you continue to watch and, lo and behold, turns to ice. Turns to ice. Its beautiful. The water boils right down the bubbles. You even see the frozen bubbles. And water boils until it becomes ice. So if youre ever with a friend that doesnt believe water is a boiling process, take him to the exploratorium in San Francisco and check that one out. Boiling is a process. Say again. Boiling is a cooling process. Boiling is a cooling process. What did i say . Water is a boiling process. Oh, gosh. Myno. Oh, hewitt, hewitt, hewitt, yeah. Yeah, water is aokay. [laughter] thank you, lee. Thank you. Yeah, but boiling really is a cooling process, gang. And when youre cooking water at home and its boiling away, you just rememberpeople, that, hey, whats the temperature of that water . And they say, a hundred degrees celsius. You turn the flame up. Whats the temperature now . [growls] theyd say 100 degrees celsius. Thats right. Turn it all the way up. [growls] really frothing over. Whats the temperature now . They say 100 degrees celsius. I know something, you know . I know that temperature of water is always the same. And then you say, well, how does it stay the same if i keep turning up the heat . And they say, well, gee, i theres probably no reason for that. Its just a property of boiling water to always stay the same. And you say what . Check your neighbor. It makes sense, gang. Yeah. It makes sense . We get the answer to such thing. Yeah. And it goes, the more heat you put in, the faster it cools and one just offsets the other, and thats what keep the temperature always the same. Really, really nice. Now, what happens if you put a cover on there . Some people say when you put a cover on top of your spaghetti that it will cook faster. True or false . False. True. The answer is true. Because when you put the cover on your spaghetti, you increase the pressure in here a little bit. Isnt that true . Doesnt the steam goes up . And thats why the cover keeps popping up a little bit. But theres a little bit more than atmospheric pressure. So thats gonna push down on the water more and thats gonna make the boiling temperature higher. So it might go up to something, likemaybe im just guessing now maybe 102. Oh, incidentally, when youre cooking spaghetti, the recipe say this, bring the water to a rapid boil and then put your spaghetti in. Why did they say that . Well, let me ask you a question. Will rapidly boiling water cook your food a little bit faster than just simmering water . And the answer begin with n. [laughter] no. The answer is no. The temperature of the water is the factor that cooks your food. And simmering water, with little bubbles, thats 100 degrees celsius. Rapidly boiling water is 100 degrees celsius. Now why do the spaghetti types tell people to bring the water to a rapid boil . Any cook types here that got an idea . Nobody got an idea. Lee got an idea. The bubbles, you know, move around the spaghetti yes. So it doesnt stick. Right on there. Youre a cook, yeah . No. [laughter] but you can do many things and one of them is cooking, yeah . I burn my food. Say again. I burn my food. You burn your food. Okay. But i bet you, when you boil, you dont, yeah . All it is, is to keep the spaghetti moving. See, if its rapidly boiling, it wont stick to the bottom of the pan. Thats it, period. So if you wanna save fuel your only fuel, bring it to a simmer, never mind the directions and then just keep stirring it, okay . Yeah. Anyway, over here, lets fasten this hood down just lid down like here. Lets fasten it right down, get it so its tight. And you see this little valve here . Lets put some bubble gum in there and block up the leak, right . Okay. Now, we put it in a stove, and we cook it. What do we call it . Beginning with b, end with a b. Bomb. Bomb. Thats a bomb, gang. [laughter] cause you know whats gonna happen. Thats the that pressure gonna build up isits gonna keep getting hotter, hotter, hotter, then [makes sound] finally explode. See, you have to have that little safety valve. And how much is gonna come out depends on how much weight you gonna put on that. You can put different value cause this squashes down so hard. This squashes down harder. Im not really sure how this works. But i think this things block off the amount of steam that can come out of there. And so finally, you will build it up to a certain pressure in there. And when you got a high, high pressure, you might bring it up the thing up to Something Like 120 degrees. Maybe youll take 120 before it starts to form steam. You see what im saying . Now, 120i mean, the steam is built up in there, but its pushing down so hard that its preventing all these little bubbles from forming, so the water heats up. Honey, youre gonna cook your potatoes very quickly in that water. How about the converse . You go up in the mountains and you just have a regular pan like this, and youre gonna cook some boiled eggs. Okay. And usually, put a you put a egg in there and you leave it for three minutes, yeah, at sea level . Now you go to the top of the mountains, you put it in there for three minutes. You take your boiled egg, you open it up, yuck. Feathers and everything. The thing is raw. [laughter] youll eat raw eggs. Why you got a raw egg . cause the water wasnt hot enough to cook it. It probably was boiling at 90 degrees, Something Like that. So the temperature of boiling water depends upon the pressure thats exerted on the water. It makes sense, yeah . Comments on stuff. Hey, thats the beauty of physics, yeah . Okay, evaporation is a cooling process. How about the converse . Condensation, when water molecules condense and form a liquid, when vapor goes to liquid state . Okay, lets just use reason. If evaporation is a cooling process, what would condensation be . Heating. A heating process, a warming process. In fact, a lot of time for in a cold climate, youre taking a shower, and you put the shower off because, all of a sudden, the telephone rings in the other side of the house. And you go streaking through the house, and then you feel cold out there. Do you know why you feel cold out there . Youre all wet. And whats happening to your body . Youre evaporating, and its cooling. And so you wanna feel warmer, so what do you do . You come back and you jump back in the shower stall, you close the door or close the curtain and youre right there. And it turns out the temperature of that shower might be the same as outside. But you feel warmer in the shower. Anyone have an idea why . Well, theres something going on there, and its not evaporation and it begins with a c. Condensation. Condensation, gang. Yeah, condensation. And whats happening is all that water vapor is coming tattooing on you, banging in you, clanging on you, giving up its energy to you, and how do you feel . You feel warmer. And if in that shower that condensation just exactly equals the evaporation, then you feel perfectly comfortable with no net change. Usually both processes happen. I mean, on a muggy day, thats a day when youre perspiring, and youre evaporating. But condensation of the surrounding atmosphere is happening at a greater rate than the evaporation. So you feel hot and sticky. So on a muggy day, you muggy day is accompanied by a warming day. Because when that water condenses, it gives up its energy, and it warms up the air. Kinda neat. Any question about that . Lee. When water vapor condenses in the air, the surrounding air temperature goes up. Yes. And how does the vapor release this energy or to the air . How does the air know to warm up when the water vapor condenses in the air . Okay, we said evaporation is a cooling process and condensation is a warming process, how does the air know to warm up . Whats the mechanism for that . Lets take a look at that. I think i can show you that, lee. Lets look at evaporation a little closer first. Evaporation, we have these molecules in here, huh . Heres the surfaces of water. Heres a water molecule here moving with a high Kinetic Energy, a high Kinetic Energy right against that one. This ones got a low Kinetic Energy at this moment. These two have a total energy that adds up to something. What happens is, this high Kinetic Energy got, boom, hits this. This one then knocks out. And this has the high Kinetic Energy. And this one over here then has a small Kinetic Energy. Can you kinda see that . The total energy is the same as before and after. But now out here, most of that the high Kinetic Energy is out in the atmosphere and the low is left behind. So thats evaporation as a cooling process. Lee, your question is the opposite one. What happens when the air molecules i mean, when molecules in the air slow down and condense . First of all, we gotta understand something. Which water molecules do you think would be most prone to condense in the air . Fast or slow . Slow. Let me give you an example. See this piece of fly paper. Okay . Now, a fly is gonna come down and hit the paper but high Kinetic Energy. Watch this. [buzzing] see that fly bounce right off. Did you guys see that . Again. [buzzing] bounce right off. Its got a lot of air, baboom, bouncea lot of momentum. Right off. Heres a slowmoving fly. [buzzing] it gets stuck. Guess what behaves the same way. Beginning with m, end with olecules. Molecules. Especially h2o molecules cause water molecules tend to stick to each other. They do that by electrical forces, something well be talking about soon. But theres a tendency for water molecules to stick. You know why the water molecules in this room right now dont condense all over the place . cause its moving more than 15,000 kilometers per hour. And these things are hit bounding off so fast. They gothey stay in the paper. But if you slow em down, theyll condense. So lets get back to lees question. Here we have a couple of molecules, Kinetic Energy another molecule. Lets suppose its h2o. Kinetic Energy Moving toward each other. Add these two kinetic energies, you get a particular value. Can these energies transfer . I mean, if i have a couple of pool balls, can i have one pool ball come inboomslow down, this one speeds up . And the energy before and the energies after are always the same . Guess what behaves the same way, begin with olecule begins with m. Molecules, okay . Lets suppose these things collide and this one here takes off with a high Kinetic Energy. Then the water molecule rebound with only a little Kinetic Energy such that this plus this add up to be this and this. Can it happen . Yeah. Now, when this does happen, and the one with a low Kinetic Energy happens to be h2o, and its near a neighbor that just did the same thing, that made some other oxygen or nitro molecule go faster and give up its energy and gets over to here, these h2os will coalesce and then become more and more happen. What happens here, this becomes a little droplet. Its not part of the air anymore. Theres your condensation. What is left behind . The air is warmer. Can you see that . So in the last bounce of h2o with the air molecule, the last bounce that gives up most of its energy to this one, and then they coalesce, that lastbounce energy warms up the air. This happens even when its snowing, especially when it snow. One time, im with my friends up at the lake tahoe, and im up at the top of the mountain. And i saidand all of a sudden, i feel it really, really getting warm. And im just kidding around and going like this, humba, humba, humba, snow, snow, snow. And someone says, hewitt, youre taking yourself too seriously. And all of a sudden hewitt, son of a gun, i underestimated you, man. And the snow is all how did i know its gonna snow . The same type thing, that room got i mean, not room that air got noticeably warmer. So in changes of state, you get an energy transfer. And i think we have a diagram in the book that looks Something Like this. Okay, you go from the solid to liquid. Does it take energy to make it go from solid to liquid or give up energy . Lets suppose this substance is h2o. Its an easy one to remember. Ice, water, steam. You go from ice to water, its gonna have to take in energy, right . Youll have to put energy into the h2o. And if you wanna turn liquid to gas, say, water to steam, you gotta keep putting the fire in, yeah . So you get energy in going this way. But how about the converse . Thats the part were talking about now. How about you go from a gas to a liquid . Does the gas give up energy or take it in . Give up. It gives it up. Yes. And how about going from the liquid to a solid, does it give it up or take it in . Give up. It gives it up. And so you go like that. And this is energy out. It used to be, before the time of electricity, a lot of farmers would get wiped out in the northern parts of america when their food would freeze. Theyd have these canning cellars, theyd be down below 6 feet level. But sometimes, it would get so cold that the darn food would freeze, it would be in jars and they would be wiped out. You know why they be wiped out . Because it turns out, when those jars of food freeze, it turns to ice and the ice does what . Begin with a ex. Expand. Expands. And it makes glass begin with a br. Break. And the food is wo. Wiped out. Okay . And the farmers feel uh. Unhappy. And thats because they dont know their f. Physics. Physics, okay . Lets look and see whats going on. What some of the farmers found out they could do. To prevent that from happening, some farmers would put down a great big tub of water right in the middle where all their cans of food are all arranged. And they keep the liquid water there, okay . Now, so long as they keep that liquid water there and that water starts to freeze and turns to ice, and before its solid ice, put some more water there, honey, theyre not gonna have that canning cellar get below zero degrees. And youll be seeing why. Because it turns out, the water is turning to what . Ice. Ice. When the water does that, whats it do . Releases energy. Its like the farmer says to his friend, hey, joe, come on over here and see the radiator i got. I got a radiator down in my canning cellar. When it gets really cold, this radiator gonna give out heat and keep my crops from going below zero. And so the neighbor comes over and walks comes down the stairs. Hey, joe, wheres your radiator . I dont see any. All i see is this tub of water. He said, thats the radiator. Thats no radiator. He says, put your hand in that water and tell me what you feel. Ooh, i feel water in the liquid state. What do you mean the liquid state . Well, the molecules are moving around with enough energy so they dont bond to one another. Enough what . Energy, huh . Okay. What happens to that liquid when water turns to ice . Where do the energy go . Oh, nowhere. It just, sort of come on, gang, where does it go . Where does it go . It gives it to the surrounding air. And as the ice freezes, it heats up the air, and it keeps that air at a nice, steady zero. Just like your water boiling stays at a hundred all the time. In this, youll keep your air at zero degrees. And your crops arent gonna freeze at zero. You know why . You could get sugar and salt in those jars, and that sugar and salt will lower the Freezing Point to below zero. And so the only thing it would freeze at zero is the stuff in that can in that big pot or other jars of water. But the jars of water, all that sugar and salt, so theyre okay. In this case, we change a state. You go this way, you get energy out. That energy will help you. Go this way, energy in. A friend just got burned. Said, oh, my god, i dont know if he got burned with steam or boiling water. But theyre both the same temperature, so the burns must be the same. What do you say . Honey, theyre not the same. Because if it was a steam burn, i dont wanna hear it was a steam burn. If it was a steam burn, that steam burn gave up what when it became water . Begin with a e. Energy. Energy. And if that energy happened to be more than the little cells are held together, well, his hands are all blistered in third degree burn. So thats what happens. That bewhen a change in state is accompanied always by an energy transfer. You go from solid to gas, gas to liquid, energy out; liquid to solid, energy out; and go liquid to gasliquid energy in, blah, blah, blah its just kinda likeair conditioners work this way. You got an air conditioner in your house, right . Whats it doing . Energy taking in or energy giving out . You can make it operate both ways. You can take the air conditioner and by the way, youd never take your air conditioner and put it on the coffee table and turn it on, would you . Thats like opening the refrigerator door on a hot day to make the room cool down. Do you ever hear anyone doing that . You walk in, they get the fridge door open. What are you doing . I wanna get cold. It wont work. In fact, the room even gets warmer. You guys know why . Energy is going out, hot air. What would you have to do to make the room really colder with a fridge door open . Take out the fridge outside. Youd have to stick the condensation coils outside, cause you got evaporation coils on the inside and condensation coils on the outside. In the condensation coils, whats happening there . Taking in energy or giving it off . Giving it off. Giving it off. And thats why you put your hand at the back of the fridge, honey, its warm. Isnt that true . Yeah. So, you guysi mean and then the motor, of course, it makes the whole thing going, will even give you a net heat increase than if you didnt do anything. So you gotta put one side on the outside. So you got your air conditioner out there, and youre feeling frustrated because all of a sudden it gets winter. Just take it around. Turn it around, and now, you got a heater. Air condition the outside out, and youll get heat inside the house. Thats why air conditions will run both ways. But you dont have to take the whole machine out and turn it around. Theres a little switch that will do it for you. So all they do is Just Exchange heat from one place to another. How . By the change of state, of liquids that easily change state from one to the other. Usually, freon. Its a cold day, so you walk in your favorite bar and you get a drink. Do they serve beer in this kind of glass, this kind of glass or this kind of glass . You guys be too young to know about this sort of thing. But let me just be telling you, most barrooms will serve beer with this kind of glass. Do you know why . Oh, evaporation. Ch, thats why. Why, sir . This kind of glass here, if thats with cold beer, whats the outside of glass gonna be . Its gonna be wet . What happen if you get beer in a glass like this and youre a little bit soft and when your holding the glass . Hey, lets toast boom, down on the floor. Glass like this oh, if you do have a glass then you have a handle like that. In germany, theyre like that, okay. But without the hand, theyll gonna slip out. This one here will slip right through your fingers. This one here starts to slip through your fingers and even if your exhaust, youll still kind of grab it and hold it. So theyre shaped like this. Also, theyll also give you a little napkin on the bottom, right . Whats the little napkin for . You say to the waitress, and whats the napkin for . She says, ch, ch. Ch . Ch. Dont you know your physics . Why the napkin . Because this stuff is gonna start to pour down. I can remember when i was a little kid. I still remember this. My father used to drink a lot of beer and he didnt want me to drink his beer. And i reached over and i took the edge cause i saw the edge was all wet. And i could take the edge and i taste it. Didnt have any taste. I thought i was i thought the beer was leaking through the glass, you see . And i said, cause its all wet. The beer get through the glass, get wet, yah . And i remember putting my hand insideooh, yucko. Why does dad drink that . You guys remember like listerine or something, you know. Really is that wetness on the outside . And i never said to my dad, hey, dad, how come its wet in the outside. My dad would have said ch, son, ch, right . We dont be knowing that. Or youd take a glass and make little rings like this on top of the table like that, you know, youd put it down. Its back with little stains thats why youre gotta put theand all that stuff unless you dont get those stains, yah . Okay, why do you get those little rings . Ch. Why do we get something your out there parking difference. Youre parking, you kinda steaming it up and your car is closed and everything. And the windows are getting all wet, okay . And your sweetheart says, how come the windows all wet . And you say what . Ch, ch. And your friend say, what mean ch . And you say what . Condensation, honey. Condensation, honey. Thats what it is, its condensation. How about clouds in the sky . How do you suppose to get the clouds . Little kid look out and say to the beautiful cloud, hey, why look at the beautiful cloud. How come the beautiful clouds . What are you usually say to a kidkids like that . Shut up kid, shut up. Dont ask questions like that. I dont know who did. Youre destroying an einstein or a mozart or something. What do you say to the kid . Ch, ch. Condensation. Its condensing up there. Remember what we talked about when we talked about the warm air rises, what if that warm air get a lot of water vapor . When that rises, whats it do . Begin with a x. Expand. Expand. When it expands, whats it do . Begin with a c. Cool. Cool. To say it cools is to say it slows down. To say it slows, to say the water molecules can what . Begin with a c. Condense. Condense. And when it condenses, what do you get . Begin with a c. Cloud. A cloud. Can you see that . Yeah. And usually the clouds around here, right over the mountains isnt that true . And why is that true . Lets look at that. This is hawaii, huh . In fact, you can always tell when youre flying towards hawaii if you wanna get to just look at the window and you see all the clouds. Its hawaii. Always clouds up here, most always. Out here . Sometimes, but most always up here. Why . Because the air its like hitting the spoiler of your car, right . Its get bounded up, right . When the air goes up, whats it do . Begin with a x. Expand. Expands. When it expands, whats it do . Begin with a c. Cool. Cools. When it cools, whats it do . Begin with a c. Condenses. Condenses. And that kind of condensation forms what . Begin with a c. Clouds. And it happens at sealevel, what do you call it . Fog. Fog. Thats right. But these updrafts, these updrafts give rise to those clouds. And thats kinda nice, thats kinda nice. I rememberi used to prospect for uranium out in colorado and i didnt know my physics then. And we used to be on San Luis Valley and go up to the Sangre De Cristo mountain range, and thats where we had some uranium claims. And we drive up there all the time and there always be clouds right over the mountain peaks. And you get up there and its cold and damp and everything. And out in the valley its dry. And i used to thats all mixed up. Why arent the clouds over here where the farmers need them. Who needs him up there . I never knew why the clouds preferred to be near the mountain. As if the cloud was an entity in itself, looking for a place to go, you know . And i didnt know about this things then, but they alwaysthat the air coming across the valley water moisture, there they are, generated right up there. So thats nice on islands with mountains. People there can then have water to drink. I got a question for you. Heres an island on the middle of pacific. Its just a great big sand bar. No elevation. Whats the chances of having clouds up above there and you wanna drink water down here . High or low . Check your neighbor. How many still say you have a high chance of getting clouds up there . Show of hands. Ooh, nobody . Ill tell you what, gang, over that land, you gonna be getting clouds because theres gonna be updrafts. When the sand be beating down on the water and then beating down on the sand which is gonna get hotter, gang . The sand. The sand. The sand for two reasons. One thing, the water is transparent and all that energy is diluted through a whole lot of water. The sand, the top part is gonna catch it. The water get a high specific heat. Take a lot of energy to change the temperature of the water. That sand is gonna get hot. You might be in the water cool, put hand and the foot in the sand, boom, its hot, like its very hot. So the air above you is very, very warm. It comes less dense. Buoyed up, cool air comes in and so the air rises up. And what does nature give that island . Clouds. Clouds. Whats the reason for the clouds, gang . Because of warm up drafts. The air goes up and the air expands. When the air expands, it cools, condenses, clouds, ccc. Neato. Turns out when air rises and expands, it cools by about 10 degrees celsius for every kilometer. The converse is true too. If the air all of a sudden nosedived down, it would heat up 10 degrees for every kilometer. There are parts of the world where in the middle of the winter the air sometimes is abnormally warm. And what happens, is Cold Mountain air nosedives down into the communities. And when it nosedives, whats it do, gang . Expand or compress . Compress. It compresses. And what compresses . Does it cool or heat . Heats. Heats. And that can heat up the whole community. Some of these are called chinooks. Winds which go up over a mountain, give off their moisture and come back down and compress, compress, and become abnormally warm and heat up the whole community. So if you compress air, you heat it. If you expand air, you cool it, kinda neat. I got a question for you. If you go about five kilometers above hawaii right now, lets say its zero degrees celsius, freezing, five kilometers high. In five kilometers high up there you have a great big dry cleaners bag. A great big, huge baggie filled with that zero degree air. And that baggie is up there floating like a balloon, yah . But its got a rope on it. And you take that rope, and you put it in a winch and youyou pull that baggie down quick, whoo. When that baggie gets to the bottom, will it be zero degrees . What will its temperature be . Think about that. Thats physics. Later. [music] captioning performed by aegis rapidtext funding for this program was provided by the Annenberg Cpb project. Even after 3,500 years, the hieroglyphics on this ancient egyptian obelisk