00:00:00 Tempest in a Test Tube, a series of experiments designed to explain the mysteries of chemistry

00:00:15 and the laws that govern them, produced by KQED San Francisco.

00:00:28 In cooperation with the California Institute of Technology for the Educational Television

00:00:43 and Radio Center.

00:00:47 And now let's go to our laboratory and meet Dr. Harry Sello.

00:00:52 Hello, in a previous show we talked about the various compounds that the element carbon

00:00:59 can form in reacting with other elements.

00:01:03 Carbon however has the property that it can form many compounds by reacting with itself.

00:01:09 This particular show we shall talk about such compounds.

00:01:13 The compounds of carbon, those in which one carbon atom can react with other carbon atoms.

00:01:23 This burner is being fed by a gas contained in the cylinder.

00:01:30 The gas is ethylene.

00:01:33 Ethylene is just such a compound of carbon, that is, it contains two atoms of carbon and

00:01:39 four of hydrogen.

00:01:41 In the molecule ethylene, the two carbons are hooked together.

00:01:45 This is the particular property of carbon about which we speak.

00:01:50 Ethylene is a gas which can be used to drive a Bunsen burner, that is to feed a burner

00:01:56 so that we can get a flame.

00:01:58 Here is the flame being generated by the ethylene in the cylinder.

00:02:03 There it is, now the air has been cut off, the flame is light.

00:02:08 If I open the air supply a little, why, the whiteness of the flame or the yellowness of

00:02:13 the flame disappears.

00:02:14 Now has enough air and we have the typical blue flame of a gas burning in air.

00:02:21 Ethylene can be used for this purpose, it can be used as a chemical.

00:02:25 However, if ethylene is treated in a particular way with particular catalysts, very interesting

00:02:30 compounds can be made.

00:02:32 Here is one of them.

00:02:33 You may recognize this little animal, it's a squeeze bottle used to squeeze out a little

00:02:39 water like I'm doing here on the floor.

00:02:43 Polyethylene squeeze bottles, these are used for cosmetics and for containers of all sorts.

00:02:49 Very popular these days because they're unbreakable.

00:02:52 Notice the difference between the ethylene which has gone in to make up this bottle,

00:02:57 it's a solid here, that is the ethylene has been made into a solid compound.

00:03:02 In the case of the burner, it's obviously a gas, the gas is burning, causing a flame.

00:03:08 Now it is of this particular kind of compound that we'll talk.

00:03:14 Ethylene is just one example.

00:03:17 I mentioned that the name of this particular material is polyethylene.

00:03:24 Let's look a little bit more at that prefix poly.

00:03:26 We're going to talk about a class of compounds known as polymers.

00:03:33 The word mer, m-e-r, the root here, means unit or one.

00:03:40 Polymer would be many units.

00:03:44 Polytechnic high school, many sciences studies, many studied there, many techniques in a manner

00:03:49 of speaking.

00:03:51 One is a figure of many sides.

00:03:57 A polymer then is a molecule made up of many units.

00:04:02 Let's write the reaction or the equation for the formation of polyethylene on the board.

00:04:12 Here is the formula of ethylene, C2H4.

00:04:20 Ethylene can be made to react with itself, that is, many molecules of ethylene can react

00:04:26 with one another to form giant molecules, which we shall write in a shorthand way this

00:04:32 way, C2H4, with a parenthesis around it and a little letter N.

00:04:38 N is just a symbol, call it number if you wish, N is just a symbol meaning a large number,

00:04:46 something of around anywhere between 5,000 and 10,000.

00:04:50 So you see what I've shown here is that N molecules of ethylene can react, 5 or 10,000

00:04:57 molecules of ethylene can react and form a long chain.

00:05:01 That chain will be composed of 5 or 10,000 such units all arranged in a sort of a row.

00:05:07 This we give the name here polyethylene, many units of ethylene.

00:05:16 This is just ethylene here.

00:05:20 This is the monomer, one unit, this is the polymer.

00:05:24 We shall talk in this talk about polymers.

00:05:29 Let's go on and look at a reaction in which we will make a polymer starting with a monomer.

00:05:37 I'll use my nice ethylene burner to warm up some water.

00:05:48 Water is just about ready to boil.

00:05:53 I'll take a second chemical here and put about an inch of it or so in the test tube.

00:06:04 That ought to do the trick.

00:06:08 Cap it.

00:06:11 Now add the catalyst into the chemical.

00:06:26 Shake it up to get the catalyst dissolved.

00:06:30 Put it here in the beaker of boiling water.

00:06:35 The catalyst now is dissolving in that material.

00:06:40 The liquid I used, which resembles greatly acetic acid or vinegar, is called acrylic acid.

00:06:48 Let's write its name on the board.

00:06:51 Keep an ear open for this test tube.

00:06:56 Acrylic acid.

00:07:03 This is the monomer.

00:07:13 I don't need to burn it now.

00:07:15 Turn it off.

00:07:20 It's still percolating along here.

00:07:25 I'll just give it a little swirl.

00:07:28 The acrylic acid is beginning to turn milky.

00:07:54 The polymer we just made is polyacrylic acid.

00:08:03 Acrylic acid being the monomer, the polymer then being polyacrylic acid.

00:08:08 Let's see if we can fish a little bit of this out.

00:08:15 That's in there pretty solidly.

00:08:19 Let's see if we can get at this material here.

00:08:25 Just be careful to hit the test tube and not the test tube holder.

00:08:34 Actually it glues the test tube together.

00:08:43 That's the glass coming off now.

00:08:48 It's a little warm yet.

00:08:50 There is the hard material on the inside.

00:08:54 Since it's warm it's still a little rubbery in nature, but now it's stiffening up.

00:09:01 Break off a little piece here.

00:09:05 Pretty tough.

00:09:07 There's a little fragment of it out on the plate.

00:09:12 This particular polymer is not a practical polymer.

00:09:15 It's a little too hard to work.

00:09:17 But in various other forms, it's a very practical material.

00:09:21 For example, a close cousin of acrylic acid, when made into a polymer,

00:09:25 is commonly called lucite or plexiglass.

00:09:28 This, instead of being acrylic acid, is actually another kind called methacrylic acid.

00:09:33 A very close cousin.

00:09:34 The same type of reaction.

00:09:36 When treated in the proper way, you can cast it into sheets.

00:09:39 The product can be cast into sheets.

00:09:41 And lucite or plexiglass can be made from this.

00:09:44 So, acrylic acid was the monomer.

00:09:46 Polyacrylic acid is the polymer.

00:09:49 A long-chain molecule.

00:09:51 Here is another example of a collection of long-chain molecules.

00:09:55 Rubber band.

00:09:58 If you've ever picked up your telephone when the receiver was all wound up in the wire

00:10:03 and tried to pull it apart, just straighten it by pulling on it when the wire is all coiled up,

00:10:08 you notice that as soon as you let go, the wire coils up again.

00:10:13 This is exactly what's happening in a rubber band.

00:10:15 The rubber band is composed of little coils of long-chain molecules.

00:10:20 These polymers.

00:10:22 When you pull on a rubber band, you straighten out these molecules.

00:10:26 So, when you let go, the molecules tend to coil up again.

00:10:30 So this is a property of polymers.

00:10:32 They like to stay in a coiled condition if they can.

00:10:35 By the way, here's a little experiment you can do with a rubber band sometime.

00:10:38 Hold it up to your lower lip and stretch it quickly.

00:10:41 And if you touch it to your lower lip right away, you feel that there's a little heat generated.

00:10:46 You see, you've exerted some energy, done some work to stretch the rubber.

00:10:51 Doing that means that it must come out in some way.

00:10:54 You get a little heat.

00:10:55 The rubber actually warms up.

00:10:59 Polymer.

00:11:01 Let's go on then and look at some more examples of different sorts of polymers or plastics.

00:11:07 By the way, the chemist quite often uses the words polymers and plastics interchangeably.

00:11:12 However, he shouldn't.

00:11:14 The word plastic refers to a kind of property or perhaps a commercial material.

00:11:20 Most everything that's made synthetically in a laboratory these days is called a plastic.

00:11:24 Polymer is the more correct word.

00:11:26 This describes exactly what the material is.

00:11:29 Now, here we have a little bit of a monomer, which I'll pour into the beaker.

00:11:36 Make sure it all gets warmed up.

00:11:48 And I'll put in with it another chemical.

00:11:58 The first material I used is called phenol or carbolic acid,

00:12:04 a common material to a chemist composed of carbon, hydrogen, and oxygen.

00:12:10 The phenol is.

00:12:12 The second one I poured in is a solution of formaldehyde.

00:12:15 Some of you who have taken a little bit of zoology will recognize what formaldehyde is.

00:12:21 Let those warm.

00:12:26 They're simmering a little there.

00:12:28 Now, the catalyst.

00:12:32 Oh, by the way, there was an experiment I wanted to show you about the catalyst in this last sequence.

00:12:39 We'll have time to look at that in the later part of the show.

00:12:44 Here is the catalyst in this case.

00:12:46 It's hydrochloric acid.

00:12:52 The reaction occurs almost immediately or starts to occur.

00:13:00 Some white material is forming.

00:13:04 There, that ought to be enough.

00:13:08 The bumping is due to the poor heating of the liquid.

00:13:12 Now, that's fine.

00:13:14 Put it right out here where it doesn't go too quickly.

00:13:20 There is a strong odor of acetic acid being liberated because acetic acid is used as a solvent for this reaction.

00:13:29 And the reaction is generating heat, you see, even though it's not on the hot plate any longer.

00:13:35 Yeah, quite stifling, I might say.

00:13:38 In fact, I will say, quite stifling.

00:13:43 There it is, perking away all under its own heat.

00:13:47 This is a demonstration of what a reaction to form a polymer can do.

00:13:52 And quite often generate a lot of heat.

00:13:58 Now, let's get this back here where I can get in and stir them a little bit.

00:14:02 There it is, forming a solid now.

00:14:06 Big, sludgy solid.

00:14:12 And there, she's just about finished.

00:14:14 Let's pour a little bit of water in here to dilute that acid.

00:14:16 It's getting a little unbearable.

00:14:20 Now, to see what the polymer looks like, I'll pour it into this jar of water.

00:14:28 There's the gooey mess.

00:14:36 There is the hard, well, it's all full of solvent.

00:14:40 This water is making it wet.

00:14:42 It's a solid material, rubbery in spots because it's quite warm.

00:14:47 This particular polymer, formed from phenol and formaldehyde,

00:14:53 is quite often given the name a phenol formaldehyde resin or plastic.

00:14:58 It is the same sort of material that forms the polymer we know commercially as Bakelite,

00:15:03 used in handles for pots, telephones, so forth.

00:15:09 This is a sample of white material.

00:15:12 Bakelite is named after the man who invented it.

00:15:16 There is a sample of material just like Bakelite.

00:15:20 Now, here is just what happened.

00:15:22 I'll show you this on the board.

00:15:25 Here, if you just look at this portion, this funny-looking six-sided material

00:15:32 with the OH attached to it, that's phenol.

00:15:35 The center structure is provided by the formaldehyde.

00:15:38 So here you have what we call the monomer.

00:15:42 I'll put a parenthesis around the monomer.

00:15:44 Here's a little N.

00:15:46 This unit, this pair of units, is repeated many times in the chain.

00:15:50 I only wrote one, two, three such links, two ends and two in the middle here.

00:15:58 If this were repeated many thousands of times, you'd have that structure of the Bakelite.

00:16:03 Again, it's a long-chain molecule, quite rubbery in nature and beginning to solidify now.

00:16:09 The catalysts which are used to form these polymers are themselves very interesting materials.

00:16:16 In the case of the formation of polyacrylic acid, I used a catalyst called benzoyl peroxide.

00:16:23 Let's look at one of the properties of benzoyl peroxide.

00:16:39 Let's cut down that roaring noise a little bit.

00:16:47 There.

00:16:48 Here is some of the white powder.

00:16:50 This is a compound of carbon, hydrogen, and oxygen.

00:16:54 I'll just hold a little bit of this in the burner flame.

00:16:58 Watch what happens.

00:17:00 It just sort of disappears in the big puff.

00:17:02 There it is again.

00:17:04 Try a little bit more.

00:17:05 Nice one.

00:17:09 It forms little streamers as it burns.

00:17:15 Benzoyl peroxide is a very reactive material.

00:17:18 The reaction to form polymers will not start unless such a catalyst is present.

00:17:23 Well, benzoyl peroxide isn't a catalyst for polymerization universally, but it is in this particular reaction.

00:17:30 A very reactive material.

00:17:31 By the way, I rang in a funny word there.

00:17:34 The word for forming polymers, the reactions to form polymers, is called polymerization.

00:17:42 Very simple.

00:17:43 The formation of polymers, or in short, polymerization.

00:17:48 Polymerization.

00:17:50 Let's go on then and look at the properties of some more polymers.

00:17:53 For these, I won't need the glasses.

00:17:56 Now I can see what I'm doing.

00:18:00 Here is a particular monomer.

00:18:02 Sort of a very gooey material.

00:18:05 Looks like a heavy oil.

00:18:07 Kind of milky looking.

00:18:11 I'll pour in first mysterious compound A, which is water.

00:18:18 Just to help this reaction along.

00:18:20 And quickly right after it, the catalyst.

00:18:27 Now comes the part to work.

00:18:41 Since this is a very viscous material, a very thick, it requires a little bit of mixing in order to get the catalyst spread out throughout the solution.

00:18:51 It shows that chemists occasionally do some work.

00:19:06 It might cook up in the kitchen, although not edible at all.

00:19:10 There, I think that's mixed enough.

00:19:13 I'll just consider it finished.

00:19:16 Let's put this down, allow it to stand here, and then go on to the next reaction and see what happens to this one in the meantime, in just a few moments.

00:19:26 Whoops, things are happening already.

00:19:27 That won't do.

00:19:29 Oh, shucks.

00:19:30 That'll come right out on the table.

00:19:32 Clean it off afterwards.

00:19:34 The dough is rising, sort of.

00:19:39 Let's go on and look at the next reaction and the formation of polymers and allow this one to move along as it will.

00:19:47 Hard not to play with it.

00:19:49 Just wants to keep coming out of there.

00:19:52 Now, just leave it alone.

00:19:54 Don't touch it.

00:19:56 Here I have a solution of a natural polymer.

00:20:01 This is a solution of cotton.

00:20:03 Cotton is composed of cellulose, and cellulose is a polymer which occurs in nature.

00:20:09 It's made up of many units called glucose units.

00:20:13 I'll take out a little sample of this solution of cellulose in the syringe.

00:20:19 It's a rather wicked-looking piece of equipment.

00:20:28 Put the sample up in there.

00:20:29 It's kind of thick itself, and it comes up only slowly.

00:20:39 Come on, rise up there.

00:20:44 Ah.

00:20:45 Now, there's about five milliliters of cellulose solution.

00:20:51 I'll now inject this into the acid in this cylinder.

00:20:59 Watch what happens.

00:21:02 Long, white threads of cellulose are forming, and they're floating up to the top.

00:21:07 Let's repeat that once more with another sample of the cellulose solution.

00:21:14 The cellulose solution is dissolved in sodium hydroxide.

00:21:19 The cylinder contains sulfuric acid.

00:21:22 When the sodium hydroxide is neutralized, why, the cellulose comes out in the form of a precipitate,

00:21:29 in the form of threads, because the cellulose solution is ejected through the hypodermic needle.

00:21:36 This type of method is used commercially to make these threads.

00:21:40 These are rayon threads.

00:21:43 Of course, not hypodermic needles.

00:21:46 These aren't used.

00:21:47 Actually, spinnerets are used, tiny, hundreds and hundreds of tiny little needles,

00:21:51 all ejecting solution-making threads.

00:21:54 Here's another batch of polymer.

00:22:03 Long, silky, thread-like materials.

00:22:08 The bigger the hypodermic needle is, the more thick the threads will be.

00:22:14 Actually, these are not perfectly formed at all.

00:22:17 They're kind of gooey.

00:22:22 I can't seem to fish it out.

00:22:23 They're so thick.

00:22:24 Here's some right in here on the end of the spatula.

00:22:26 I just dumped it right out on the table there.

00:22:31 Cellulose, then, is a natural polymer, and here is one way in which it can be changed to something commercially useful.

00:22:38 Not this particular stuff, but rayon is.

00:22:41 If you look back at the previous sample of polymer that was made, it's all solid now.

00:22:50 Actually, it's very rubbery.

00:22:55 A little bit tacky, but you can see I can bounce it.

00:22:58 It's rubbery.

00:22:59 Here's a sample of the same material that I made a few minutes ago, before the start of the talk.

00:23:03 It has the shape of the bottle even, just came out the same way.

00:23:06 It's quite rubbery.

00:23:07 This is a kind of foam rubber called urethane rubber.

00:23:11 I'll just write the name of this on the board.

00:23:20 Urethane rubber.

00:23:24 This kind of foam rubber, for one thing, is a little bit better in one respect, I should say, than the usual type of foam rubber.

00:23:31 It cannot burn as easily.

00:23:33 It's not quite as flammable.

00:23:34 A little stiffer, has many uses as pads for cushioning blows.

00:23:38 Let's go on then in this matter of natural polymers and look at yet another kind of natural polymer.

00:23:46 For this, we have the following setup.

00:23:50 I'll pour into these test tubes a little bit of hydrogen peroxide, concentrated hydrogen peroxide.

00:24:04 Now, to make this reaction work, we need a sample of human blood.

00:24:16 I just happen to have some.

00:24:19 I hope.

00:24:26 I have a spare finger here somewhere.

00:24:45 There's a little bit. Let's get a little bit more.

00:24:53 It's leaking all over the place here.

00:24:56 I can't hit the finger. It's too long a tube.

00:25:03 My pen's stuck.

00:25:06 Now then, keep coming, blood.

00:25:19 Sort of a vampire effect here.

00:25:26 Now I'll put this little sample of blood into one of the test tubes.

00:25:44 Make sure I have it all out there.

00:25:48 Notice that the test tube, the liquid in the test tube immediately turned milky and is developing a bit of a foam at the top.

00:25:56 I'll stir this one just to show that the actual stirring isn't what's in it.

00:26:02 The blood, the sample of blood, which I took by donating a little bit of myself here, contains in it an enzyme called catalase.

00:26:15 Enzymes are naturally occurring polymers. They are proteins, polymers of carbon, hydrogen, oxygen, and nitrogen.

00:26:21 We can have many of these in our bodies.

00:26:24 This particular enzyme, this particular polymer, has the ability to cause hydrogen peroxide to decompose and form this particular foam.

00:26:33 There it is still foaming a bit.

00:26:36 Whereas without the enzyme, the hydrogen peroxide will not decompose.

00:26:41 Since the experiment was successful, we won't need all this auxiliary equipment.

00:26:47 Well, let's look back and see what we've learned about polymers.

00:26:54 A polymer is a long-chain molecule.

00:26:58 The word means many units.

00:27:01 Polymers are composed of monomers.

00:27:05 Monomer means one unit.

00:27:07 This comes about because carbon atoms have the ability to react with one another and form chains.

00:27:14 We made some polymers.

00:27:16 One of the ones we made at the start of the show was a polymer made from acrylic acid.

00:27:21 This was that popcorn reaction so-called.

00:27:24 It formed polyacrylic acid.

00:27:27 We showed a polythene squeeze bottle.

00:27:29 This is a form of polymer.

00:27:32 We then went on to prepare a common polymer.

00:27:35 Sometimes these are called plastics.

00:27:37 This was a polymer formed by phenol and formaldehyde reacting together.

00:27:42 It formed a resin, the structure of which is shown on the board.

00:27:47 Then foam rubber, also an example of a polymer.

00:27:52 Then the naturally occurring ones, cellulose.

00:27:56 Finally, the bloodletting experiment, the formation or the collection of the sample of natural polymer, the enzyme catalase.

00:28:05 This caused hydrogen peroxide to react in this particular reaction.

00:28:13 With the formation or the collection of this enzyme, this brings us to the end of the talk on polymers.

00:28:19 Thank you.

00:29:07 This is national educational television.