What did you not know that? >> All right. Good afternoon. People out to do today. You're correct strategy is going to be to not try to write everything down. You're correct strategy is going to be to go back ten minutes after class and watch the ED captures video, videos and pause when necessary so you can catch up on whatever you missed. In other words, I'm going to open the fire hose and here it comes. >> Today, work factor six. >> We do want to finish talking about the chemistry of the major nonmetals, metalloids. Each slide I show you will be on screen for approximately three minutes, beginning with silicon. >> Silicon is actually a metalloid. >> A famous chemist by the name of John's jack up or accidentally discovered silicon and a number of other elements as well. Silicon is the second most abundant element on earth, and it won't be too much of a surprise as to why that's true. And we see how many different things silicon dioxide, SIO2, shows up in. And that formula is a little bit misleading, will show you why in a few moments. There are three major isotopes and silicon. Silicon twenty eight, twenty nine, and thirty of which silicon 28 makes up more than 90%. Single dioxide is basically sand. So sand is an abundant natural resource that we can use to get elemental silicon from carbon as a reducing agent, can we get rid of the oxygen from silicon dioxide to give you basically pretty close to pure silicon and carbon monoxide as the byproduct. Silicon dioxide is also the major component of things such as courts, pupils, and amethysts. Many different gemstones contains silicon dioxide mineral Flint used to make arrowheads, glass and cement also contain largely Silicon dioxide, along with a few other things thrown in there to give them their particular properties that they have. >> Mm-hm. >> Variations on the theme. Let me show you some pictures of what some of these things look like. Silicon is in group four on the periodic table. Like carpet is unlike carbon, which has a strong tendency to bond to itself, silicon has a tendency to bond to oxygen. And since an oxygen atom can bond to more than one silicon atom, we get tetrahedral patterns of silicon oxygen bonds. Looking like this when you extend them in different dimensions, creates silicate structures that look something like this. >> There are better pictures in your textbook. >> So silicates or species like what we just showed you that contain either SIF for four minus ions or the sheet-like structures that we just showed you before. >> One of the most common silicates is zirconium. >> Silicate used in the MIT are found in the mineral zircon. You've heard a cubic zirconia imitation Jenner jewelry. That's basically what that is. Zirconium silicate is also an abrasive that has been used in toothpastes and poly silicates are all celebrations minerals such as talc, Micah barrel, and of course the nasty one that everybody thinks of when they think of silicon compounds, asbestos. We've learned that we don't want to put his best, those who do building materials anymore. But when old buildings get demolished, that's one thing that everybody has to watch out for is the presence of asbestos in the old building materials. The difference between silicates and silicones is it's silicones contain silicon carbon bonds, such as what we show you when things like this, that tends to make them a bit softer, a bit more flexible. And they have applications and things like caulking materials that people would use around their backups in their houses. Silicone oils are used as lubricants. They're found in ceramics. And here's one. I don't know if this is still available or not. You tell me what your childhood was like. >> You guys play with silly budding. >> Okay. >> It's called Silly buddy that because it does silly things, although it does because it's made of silicones. >> Bless you. >> To the right of silicon on the periodic table, we have phosphorus leonard, He's nitrogen group five, has some things in common with nitrogen, others not. >> For one thing, phosphorus is a solid. >> It was discovered in 1669 by a German chemist by the name of heading bronze to major isotopes of phosphorus. By far the biggest isotope of phosphorus, the most abundant is phosphorous. >> 31 >> But phosphorus 32 is a radioactive isotope of phosphorus that's commonly used in radioactive tracer and labeling studies. The allotropes of phosphorus are known by colors white phosphorus, red, phosphorous, and black phosphorus, of which white phosphorus is probably the most interesting. Phosphorous occurs naturally in the form of various phosphate minerals, such as calcium phosphate. Again, if you heat this up using carbon as a reducing agent, you can get rid of the oxygens attached to the phosphorus and leave yourself with elemental phosphorus, which has the formula P4. >> That's white phosphorous. And here's what its molecular structure looks like. >> It is a tetrahedral molecule in the sense that there's a phosphorus atom at each corner and what would ordinarily be a tetrahedron. But the point is that p4 is actually a very strange molecule. >> And here's what we mean by that. >> You'll notice that each phosphorus atoms is bonded to the other three and has a lone pair on it. By the rules for forming hybrid orbitals that we talked about in Kent 101, that will make an sp3 hybridized with bond angles of 109 degrees. However, when it adopts this geometry, each face of the tetrahedron is actually an equilateral triangle. An equilateral triangles have an interior angle of 60 degrees, excuse me. The difference between what the angle must be by the laws of geometry and what I would like to be based on the hybridization of the atoms is 49 degrees. That's a significant amount of what's called angle string. >> To relieve that angle string, phosphorus is very react it with oxygen. >> It reacts with oxygen to form compounds like P40 six and P4 010. And I believe I have a picture of what those look like. Here's P40 six on the left side. Here is P4 010 on the right side. And the point is the little teal colored circles here represent the phosphorus atoms. I hope when you look at them in this picture, you'll see that they are much more like the 109 degree angles that we normally associate with tetrahedral sp3 hybridization. Oxides of phosphorus, like the oxides of other non-metals, tend to react with water and form acids. >> Notably, phosphor us acid H3PO4, phosphoric acid H3PO4, absolutely. >> What are phosphorus compounds used for? There's phosphoric acid in carbonated beverages. >> Hang on a minute. >> I'm just looking at the side of my bottle of Coca-Cola, by the way, to see a recent news item, drink sugary drinks. >> Mottos with artificial sweeteners. >> Artificial sweeteners have been linked to increased probability of stroke and dementia. So I'm enjoying my Coca-Cola here today. I don't know if we're going to be able to see this or not, but I'll try that right down here on the label, right where my finger is. >> Zoom in, zoom in, zoom in, zoom in, zoom in, zoom in, zoom in. >> That's going to be too pixelated. Anyway, it says phosphoric acid that adds tartness to the Coca-Cola tends to make it grab your tongue a little bit more. Anyway, the point is, there is phosphoric acid in carbonated beverages such as coke from high school biology class, or maybe college biology class. >> You've probably heard of compounds like adenosine, triphosphate, ATP at a desk. >> Diphosphate ADP used for biological energy storage and transfer. There was a question on the last exam about that. We've talked about hydroxyapatite, which is basically calcium phosphate. That's the mineral that's in your bones and your teeth, makes them strong. A class of compounds called phospho lipids, which you'll probably find out more about some future biochemistry class, is useful as a protective material to surround the tissues of the brain and nervous system. >> Phosphates are used in fertilizers, toothpastes, and baking powders. But unlike what it says on my lecture notes, which are old, old, old not used in detergents anymore. >> I have some discussion to the lecture notes as to why. But this one handout that I've given out today is actually a better article that explains more about why phosphates are no longer used in detergents. Caption down here says it won't be long before phosphate detergents disappeared from store shelves. This article was written in 2010. >> Chances are they're already got red phosphorus gives match heads their characteristic a red color. >> It's also used in fireworks. And black phosphorus, which is actually the most stable of the three allotropes as semiconductor properties. >> So it's used in the electronics industry. >> Yeah. >> Let's talk about sulfur for a few minutes. Nobody knows he discovered sulfur. >> Sulfur has been known since antiquity. >> The major isotopes of sulfur include sulphur 32, sulfur 33, sulphur 34, and sulfur 36. Most silver is sulfur 30. Do most of that which is not is sulfur 30 for the major allotrope of sulphur is sulfur eat. And here's a picture of a molecule of sulfur eight. It's eight sulfur atoms arranged in a crowd shaped ring looking something like this. Silver is actually found in underground deposits at his mind by a process known as the fresh process. There are silver mines in places like Texas and Louisiana, among others. Let me just briefly show you a diagram of what the fresh process looks like. If this is an underground sulfur deposit and here's the surface of the Earth. Up here, what's done is to sink a tube down into the sulfur deposit. Inside that tube are several concentric tubes, some of which contain hot water in the form of superheated steam. You force it down there and it melts the sulphur. Then you're forced compressed air down another tube, and that pushes the molten sulfur up to the surface where it can then be collected. Sulfur is used in gunpowder and it's also used in a process known as the vulcanization of rubber. Now to tell you what this is all about, rubber is basically long strands of carbon atoms looking something like these guys right here. As you know, rubber is a soft, generally flexible material. This process known as the vulcanization of rubber involves adding sulphur to the rubber. And what happens is the sulfur tends to form what are called cross-links between the carbon strains. What that tends to do is make the Suffer salt guys tend to make the rubber tougher, more durable, more able to serve the function of things like car and truck tires. In other words, there's all different kinds of rubber. Theirs remember, like you would use in a balloon and there's rubber like you would use in a car tire. And the point is the tougher vulcanized rubber is much more useful for that. It shouldn't be too surprising to find that a fella named Charles Goodyear develop this process and then went on to found the Goodyear Tire and Rubber Company. Interesting things that sulfur, sulfur compounds can be used for other than vulcanization. Solver, like other non-metals, reacts with oxygen to form oxides such as sulfur dioxide and sulfur trioxide, which when they react with water, form acids. Sulfuric acid comes from SO2 sulfuric acid comes from, and so three, by the way, since these guys are gases They contribute to the acid rain problem over most of the Northeastern United States. High sulfur content Coke, such as what we find in West Virginia and western Pennsylvania, places like that. When you burn, it releases these gases into the air where they eventually find water vapor and return these things to Earth in the form of acid rain. Sulfuric acid compounds are called sulfates. Ammonium sulfate is one example of a common fertilizer. >> Here's one for the food folks. >> The conjugate bases of sulfuric acid are called sulfites. And there are various sulfites that are used as preservatives and foodstuffs not to preserve the food itself, but to preserve its color. These things are commonly used in whines. The only problem is that people found out that some people, especially those people who suffer from asthma, are allergic to these things. So nowadays, when you look at the ingredients and a bottle of wine, they might say this contains no sulfites. Just to let people know that if you do have an allergy to that, you can go ahead and drink the wine and not have to worry about that. Hydrogen sulfide, H2S is a weak acid. Like most sulfur compounds. It has a rather nasty smell. H2s smells like rotten eggs. This compound called dimethyl sulfide is the compound that's actually added to the gas that's used in Bunsen burners and the laboratory to give it that gas leak smell that lets you know that it's time to leave the building because somebody left the gas jet open. The smell that's left behind when somebody runs over a skunk ON THE I owing the common smell that we associate with garlic. A large number of disagreeable odors have something to do with various sulfur compounds. >> And again, for those of you going onto a course in biochemistry, there are a few amino acids such as methionine and cysteine that contains sulphur. >> Here's the structure of a cystine molecule, actually two of them. >> It turns out that when you gently oxidize the compound like this, you could form a linkage between these two sulphur atoms that looks like this. >> This is called a die sulfide bridge, and that turns out to be a very important part of the secondary and tertiary structures of proteins that basically forces the protein into whatever geometry it needs to be in to carry out whenever its biological function happens to be. For those of you going out to a biochemistry course, you'll probably hear more about disulfide bridges at a later time. You can take ten more seconds on shakes them blood back into your hand, and then we'll keep on going. Giving over to Group seven, we find that very interesting group of elements known as the halogens. >> On probably the most interesting one, fluorine >> Fluorine was first isolated in elemental form in 1886 by a French scientist, the name of all Ramos. Same by electro chemical methods. It ran occurred of electricity through molten sodium fluoride and generated elemental F2 that way. For a long time, it was believed that since fluorine is the most electronegative element, that that was the only way that it would be possible to generate elemental florine. But a 100 years later in 1986, a fellow named Carl Christie, who was working at Rockwell International at the time, used an oxidation reduction reaction shown here to generate, among other products, elemental florine. So this is one of those. Don't ever say it can't be done because then somebody who go out and do it kind of moments. Fluorine occurs in nature in the form of minerals such as fluoride, which is calcium fluoride, and cry away, which is sodium aluminum fluoride, will talk more about cryo light later in the semester when we talk about the chemistry of aluminum. Now, since fluorine is the most electronegative element, it can do some very interesting reactions. One of them is what happens when it reacts with water. If you take elemental florine a reacted with water, you get two compounds, hydrofluoric acid, HF, an oxygen di fluoride, OF2. Now again, since fluorine is the most electronegative element, its oxidation state must be minus one in any compound in which it's found. The normal oxidation state for oxygen in most compounds is minus two. That's certainly the case for water. But in oxygen di fluoride, oxygen is actually in a plus two oxidation state. So it could be argued that since changing an oxidation state from negative to positive is oxidation, fluorine is about the only substance that can oxidize oxygen. >> In other words, it's the only substance that can make water burn if you want to think of it that way. >> Yeah. >> Alright. >> A moment ago we showed you that hydrofluoric acid can be four by that reaction between fluoride in water, hydrofluoric acid is a relatively weak acid. Ka value of 1 times ten to the negative. Fourth problem is there are two things that it reacts with strongly. >> One is glass. >> We said before that silicon has a strong affinity for oxygen, and silicon dioxide mostly makes up last. Well, Silicon, as it turns out, has an even stronger affinity for fluorine. Where etched glass comes from is dripping hydrofluoric acid onto glass to etch patterns in the glass. The other thing, hydrofluoric acid attacks is anything that contains calcium, because there's also a strong affinity between calcium and fluorine. That's why people are exposed to hf are in trouble because this thing attacks their bones and their teeth and the very framework of their body. That's why people who work with this stuff swab themselves and layers and layers of clothing and make sure they don't inhale any of this stuff. Here's the reaction between hydrofluoric acid and the silicon dioxide and glass products are water and silicon tetrafluoride. Here's an organic compound that contains fluorine. The name tetra floral ethylene comes from the fact that the hydrogen equivalent of this compound, C2H4, is commonly called ethylene. But if you replace those four hydrogens with fluorine atoms, you get a compound called tetrafluoride ethylene. I point this out because as you may already be aware, and if you're not, we'll talk more about this later on in the course. >> It is possible to make molecules like the X link up with each other and form a much larger molecules called polymers. >> And the point is that we polymerize tetra floral ecoli and make a material called polytetrafluoroethylene. The polytetrafluoroethylene looks like this, but little dots at each end just mean that this sequence of CF2 is repeat themselves over and over again many times. These are great big molecules of molecular weights on the order of a billion or so. Does anybody know what the common name for polytetrafluoroethylene is. Giving you a little bit of a hint by underlining a few things in that name. Yeah, Teflon, PT FV stands for polytetrafluoroethylene, but most people just call it Teflon. >> What's Teflon? >> And most commonly used for Meno. >> Before long, this may go the way of all flesh for reasons that will become clear in a few moments for a long time. >> With Teflon is mostly used for, is coding the frying pan so that nothing would stick to the frying pan. The other handout I gave out today looks like this. It was an interview with a couple of scientists who were instrumental in the discovery of Teflon. When the title of the article refers to Teflon sticky question and shows you a frying pan there. >> The sticky question is, if nothing sticks to Teflon, how does Teflon sticks to the pan? >> And I'll let you ponder that and then you can read the article and find out more about it. But on the back page of the article, they show you basically what we showed you a few moments ago about how you can link a whole bunch of smaller molecules together to make essentially Teflon. >> Now here's the downside of that story. >> And discipline has definitely been in the news recently because as I speak to you now, it is 2017 and something has happened recently that most Delaware Ian's would've said could never possibly happen. And that is the DuPont company no longer exist as a separate entity. It is merged with Dow. And so well, Dupont was a significant employer in the state of Delaware for many, many years. There are still people working for subsidiaries of DuPont. >> But part of what helped to bring about DuPont demise is this compound. And if it looks a lot like Teflon, there's a reason for that. >> This compound is actually formed as a byproduct along with the formation of TensorFlow. It's called PR floral actin, OIC acid, or PFOA or CA for short. >> Here's the acid part right here. >> But the point is most of this molecule, as you can see, it looks a lot like Teflon. And not too surprisingly, it has a lot of properties in common with Teflon. Turns out that astonishingly, things like this tend to be relatively soluble in people's bloodstreams. There's a lot of people, perhaps including some people in this room who are walking around with PFLA and their bloodstreams. And since this hasn't been really well tested yet to find out whether this is good, bad, or somewhere in-between. >> People are a little bit nervous about this. >> As a result, a lot of people have been suing the DuPont company over PFLA. Here's a fairly recent, and in fact, this was just earlier this semester. Valentine's Day is when this particular copy of the news journal was published. >> But anyway, headline here, DuPont commuters to pay $670 million in PFOA suits. >> Pfla is this stuff which is the byproduct of Teflon. So we'll see what happens with all of this. >> Obviously, these lawsuits are going forward that this may turn out to be e combat that brought about the demise of DuPont. >> We shall see on a more everyday application when we talked about this earlier this semester. >> Brush your teeth with fluoride toothpaste, right? >> Drive that equilibrium to the right, convert hydroxyapatite to do floral appetite, strengthen your teeth. >> Fewer visits to the dentist drill, actually, you do know the grill. >> That's why you don't go to the dentist. Will you brush your teeth instead? >> Perhaps a bit more familiar than fluorine is chlorine. >> Laurie was discovered in 1774 by the Swedish scientist called, they'll help Shaylan. Two major isotopes of chlorine, Chlorine-35 and Chlorine-37 that occur in nature at approximately a three to one ratio, Chlorine-35 makes up about 75% of chlorine. Chlorine-37, about 25%. That's why the atomic weight of chlorine is not anywhere near, close to a whole number. If you take a weighted average of those two, you find that the weight of a typical atom of chlorine is about 35.5 atomic mass units. Sodium chloride makes up about 2% of ocean water. So it's not too surprising that we have a very abundant source of chlorine. If we want to run a current electricity through seawater and generate elemental chlorine. We can do so very easily. Chlorine is used in making bleach. It's these two reactions actually appear in my lecture notes on page 79. On page 79, It makes reference to the fact that they are equilibria, except it doesn't show that they are equilibria. >> On page 70, not so. >> You may want to change those reaction arrows to equilibrium arrows if you are following along in electronics the significance of that. >> Okay? >> You can make essentially Clorox Bleach by taking sodium hydroxide, which is lie at is also four for the electrolysis of sea water and reacting with chlorine to make sodium hypochlorite, which is the active ingredient in Clorox bleach. The byproduct of that reaction is HCl. Likewise, calcium hydroxide reacts and elemental chlorine to form calcium hypochlorite used in bleaching powders also with HCL is a byproduct. Today's home health and safety tip. Don't mix acid with bleach. Not that you normally would anyway, but if you did mix acid in with bleach, adding acid to the right side of this equilibrium, shifted to the left side and generates elemental chlorine. Now you know what chlorine smells like, right? Like in swimming pools and things like that. Actually only think, you know, a chlorine smells like because actually what you're smelling there are things like this. The smell of elemental chlorine is kind of like that, but much, much worse. So don't mix together acid with bleach. She'll generate chlorine and probably poison yourself. That said, we're all walking around with one very important chlorine compound inside of us. Hydrochloric acid is the acid present in the lining of your stomach that helps break down your food and metabolize it. Here's a common chlorine containing compound. This compound is called a vinyl chloride. And it turns out it's possible to link these molecules together, like we did to make Teflon. But we do that. The polymer that's formed is called PVC for polyvinyl chloride, which is a strong, tough, durable material that has pretty much taken the place of lead pipe and everybody's houses, this is the plastic that you use to transport water. Peoples houses, compounds that contain fluorine that had developed a very undesirable reputation, include chlorofluorocarbons, or CFCs, which break down the ozone layer, and DDT, which stands for dichloro di phenol. Trichloroethane used commonly as an insecticide for awhile until it found out, or until people found out that data very deleterious effect on other organisms as well. Nowadays, if we're going to spray for bugs at all, we tried to pick compounds that will target just the bugs and not anything else. >> So we don't use DDT for the most part anymore. >> Let's talk about bro me. >> By the way, there's a color coding all the slides for a reason. Fluorine is kind of a light yellow gas. >> Chlorine, a greenish yellow glass gas. >> Bromine is a reddish brown liquid. So I decided to write this slide up using reading. The bromine was discovered in 1826 by a French scientist named Antoine Jerome by lard. The atomic weight of bromine is approximately 80, but there are no bromine atoms that way. At half of them weigh 79.5 of them weigh 81. So we take an average and we get a number that's pretty close to 80. Bromine is the only non metal that happens to be illiquid. The easiest way to generate elemental bromine is to expose elemental chlorine, it to some robot containing salt and oxidize it so as to make elemental BR2. Here's one application that is useful in the food industry. You've all done titrations At this point. C, you know how to do that. Normally, when you do an acid-base titration, you have to add a little bit of an acid-base indicator so that something changes color when the titration is over. >> Turns out that bromine can be use in the analysis of saturated and unsaturated fats. >> What makes an unsaturated fat unsaturated is the presence of a carbon carbon double bond. The case of a poly unsaturated fat, numerous carbon-carbon double bonds. If you want to find out how unsaturated your unsaturated fat is. >> You can take a sample to fat and titrate it using bromine is the tightrope. >> Bromine is reddish bromine when it reacts with compounds that contain a carbon, carbon double bond gives you a structure that looks something like this. The point is though, that when the elemental bromine is consumed, this compound essentially has no color. So the point is, as you add the red bromine to your fat, that you're titrating. The color keeps on going away and keeps on going away, and keeps on going away until finally, you've reacted all of the double bonds to make this kind of thing. And then the next couple of drops of bromine, the color doesn't go away. And that's how, you know you've reached the end of that iteration and you can make some sort of a quantitative statement about how unsaturated your unsaturated fat happens to be. I mentioned before that my lecture notes are older than you are. Therefore, you can ignore the reference to ethylene di bromide in your lecture notes. It's really not being used as a gasoline additive anymore. So fluorines, yellow chlorine is green. Bromines read, IT turns out to be purple. I mean, was discovered in an interesting way in 1811 by French scientist by the name of Bernard Kerr. Twa Kurzweil was actually a marine biologist and he was studying kelp, that he treated the kelp with sulfuric acid. And he knows this cloud of purple stuff coming up, which we found out later was elemental iodine that was coming from the kelp that had been acidified. Among the important isotopes of iodine, the most important and naturally occurring isotope is iodine 127. Iodine 131 is synthetically produced, and we talked about this a little bit earlier when we were talking about the different ways that radioactive materials can be used in medicine. This is the stuff that is fed to patients that have conditions of the thyroid gland because the thyroid absorbs iodine. And so the point is that there's a disease in the thyroid gland that you want to do something about. One approach to doing that is to target just the thyroid gland using radioactive iodine. We talked about a condition called Grave's disease that former President George H W Bush and his wife, Barbara Bush, both suffered from while he was in office. Suffice it to say that this is a successful treatment for that condition for them and they're still with us today. Iodine is prepared it chemically from potassium iodide using oxidation reduction reactions. Iodine, as we said before, is a purple crystalline solid which tends to sublime. That is to say when you heat it up, it goes directly from the solid state to the gaseous state. That's kinda what Kurzweil was seeing when he treated these things with sulfuric acid. That's an exothermic reaction. And so we got clouds of iodine gas that way. Most of the time when people think about IT, they think about something. They put out a cut to disinfect that, that's a liquid of, well, what that is, is a solution of iodine and ethyl alcohol. That's called tinctures of iodine. >> That's the stuff that's commonly used to treat a wound. >> As I mentioned before, at thiamine is absorbed by the thyroid gland to make a hormone called thyroxin. I think there's a picture of thyroxin somewhere in your textbook. I'll let you go and look that up. So these days when you go to the store to buy salt, generally what you wind up buying is a container, what's called iodized salt. >> Salt, of course, is mostly sodium chloride. >> But since people may not get quite enough iodine in their diet to make the right amount of this, this hormone, you can add a little bit of iodized salt to your food. Iodized salt also contains potassium iodide. That's a way of getting a little bit more iodine in your diet if you're concerned about proper thyroid functioning I did have one demonstration that I wanted to show you today has to do with some phosphorous and sulfur chemistry. But I didn't think it was going to have time to get to it, so I didn't prepare that for today. We'll show that to you at some later time. Here is the last slide for the day, the last group of elements that are nonmetals that we haven't said much about at this point are the noble gases called noble gases as opposed to inert gases? Because for awhile it was believed that they would never react to form compounds. >> So they were considered to be inert. But in relatively recent years, beginning about the 19 sixties, scientists found that some of them, notably xenon and krypton, could make some compounds as shown here. >> So now they're called the noble gasses in the sense of they still don't really want to make compounds that I don't think anybody has made any compounds from helium, neon, or argon yet. But the main point is that it's possible for them to react, so they're not called the inert gasses anymore. So since for the most part they don't make compounds, all we can really talk about, here's what they're used for. So what's helium used for? >> Balloons. >> You can make helium filled balloons for parties. You can use helium is the lifting gas in blimps such as the Goodyear Blimp. And in case there are any scuba diving enthusiasts here, a mixture of helium and oxygen is commonly used in scuba tanks to avoid the condition known as the bends. If you breathe regular air, which is mostly a mixture of nitrogen and oxygen, it turns out that nitrogen is much more soluble in the bloodstream that helium is. When you resurface, it comes bubbling back out of your blood. That's a very painful condition known as the band's breathing. A mixture of helium and oxygen avoids that. And of course, the only problem with that is that when you breathe helium, vegetables go up like this. >> You know that, right? >> Maybe someday I'll try that with a helium filled balloon. What's me unused horn? >> Yeah. >> Signs that glow? >> Yep. By the way, the color-coding that I'm using here, in principle, you could make a neon sign using any of the noble gases and you would get different colors if you did. >> Neon is most commonly used because it glows bright orange. And that's very eye-catching and attention getting. Argon actually makes up about 1% of the Earth's atmosphere, so it is easily the most abundant noble gas. Argon is used in making lasers. To make laser light, you have to pump some material up to a high energy state. And when it comes back down, it gives off that bright light that we associate with a laser. It's also used as an inner atmosphere to try to minimize any damage done, say, during a welding process with a lot of sparks flying all over the place. >> Krypton is not used to kill Superman. >> That's kryptonite, which doesn't really exist. >> Krypton gas is used in light bulbs to prevent the filament from burning out. >> Another inert atmosphere. Likewise for Xena. Xena as used in the high brilliancy lights that are commonly used in baseball and football stadiums and things like that to create very bright lighting. And we talked before about the problem of radon in people's basements and things like that. But it turns out that there are some treatments for patients with cancer that actually do involve exposing them to read on. So just as it turns out that some radioactive materials can cause cancer, you could use other radioactive materials to help cure cancer. >> Freedom radon is sometimes used for all right. >> We'll see you on Wednesday for your exam. If there are questions between now and then, feel free to stop by my office hours or send me an email. >> Come on. >> Yeah. >> Or like the structure is that every job we have to remember all that. >> Well. Here's the boy. >> Anything we've been talking about lately is fair game for your exam. So obviously we can't ask about all of it. That would be like about ten hour exactly. So where does that Jews are there? >> So the answer your question is more of those things, you know, the better shape we're going to do. >> Well, I don't think there's anybody here. Not really. Right. Yeah. Yeah.
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From Dana Chatellier October 11, 2018
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