00:00:00 This is a production of the U.S. Department of State.

00:00:04 Any resemblance to persons, living or dead, is coincidental and unintentional.

00:00:09 This film was made with the support of the U.S. Department of State.

00:00:30 TEMPEST IN A TEST TUBE

00:00:37 A series of experiments designed to explain the mysteries of chemistry and the laws that govern it.

00:00:45 Produced by KQED San Francisco.

00:00:54 In cooperation with the California section of the American Chemical Society.

00:01:03 For the Educational Television and Radio Center.

00:01:09 And now let's go to our laboratory and meet Dr. Harry Sello.

00:01:14 I would like to talk this time about a matter concerning secret agents.

00:01:20 Hello. Secret agents of chemistry that is.

00:01:28 There are some materials which in chemistry are called secret agents or are referred to as secret agents.

00:01:37 This is a sort of a name which glamorizes them but has some merit.

00:01:41 These materials which I will talk about this time are catalysts.

00:01:47 A catalyst, which I will show you, is a material which participates in a chemical reaction and makes it go faster.

00:01:56 Speeds up the chemical reaction.

00:01:59 The word originally means loosening up.

00:02:02 That is, sort of loosening things so that they can go faster.

00:02:07 Here is an example of a catalyst.

00:02:15 I have a little bit of black powder here.

00:02:19 Blackish powder that is, nothing to do with the explosive black powder.

00:02:25 A material which is a powder form in this dish.

00:02:33 To illustrate the effect of the catalyst, I will use a little bit of hydrogen peroxide.

00:02:41 Hydrogen peroxide looks like water.

00:02:44 I drop it out here in this other dish.

00:02:47 Nothing particularly exciting about it.

00:02:52 But now watch what happens when I drop hydrogen peroxide in this dish.

00:03:02 There is an immediate reaction.

00:03:05 The black powder that I put in there is still a black powder.

00:03:09 Slightly wet.

00:03:12 The hydrogen peroxide has decomposed.

00:03:15 This black material, in this case, is the catalyst.

00:03:20 It is manganese dioxide.

00:03:25 I'll just cover the hydrogen peroxide because it is corrosive.

00:03:29 And when spilled, can cause damage to the fingers, the desktop, other material around here.

00:03:36 Why is hydrogen peroxide such a good reaction for the study of catalysts?

00:03:40 Let's write the reaction on the board and just see what happens.

00:03:47 The formula for hydrogen peroxide is H2O2.

00:03:53 Note the similarity to water.

00:03:55 Has one more oxygen atom in it than water has.

00:03:58 Hydrogen peroxide decomposes very easily.

00:04:02 The arrow means, in this case, decomposes to water and oxygen.

00:04:13 I must also balance this reaction, that is, write it in its proper proportions.

00:04:22 Two waters, one molecule of hydrogen peroxide, two molecules of water, two molecules of hydrogen peroxide, one molecule of oxygen.

00:04:31 This means when hydrogen peroxide decomposes, it forms two products, water and oxygen.

00:04:37 The white fumes that we saw just then was the water vapor.

00:04:42 The oxygen is invisible.

00:04:45 Let's look further then and see how we can use a catalyst to affect a chemical reaction.

00:04:51 We just demonstrated manganese dioxide.

00:04:57 Here is another solution of hydrogen peroxide.

00:05:05 It pours easier with the cap off.

00:05:15 Put some in each cylinder.

00:05:24 We might as well make it even.

00:05:34 Because hydrogen peroxide gives off a gas which can't easily be seen, let's add a little soap suds just to make the reaction visible.

00:05:43 I'll add some soap suds to both.

00:05:53 A little bit of foaming due to the soap suds.

00:06:03 Now, the catalyst.

00:06:08 Ordinary yeast, baker's yeast.

00:06:15 Just a little bit, shake it again.

00:06:20 Shake this one just to show that the extra shaking didn't do it.

00:06:28 There is the hydrogen peroxide decomposing very rapidly in the presence of the catalyst.

00:06:33 Because the oxygen is charging off from the liquid, it carries the soap suds with it.

00:06:43 The whole cylinder is filled with soap suds and there's a great big pile of it accumulating around here.

00:06:52 You get a nice clean tabletop as a result.

00:06:55 The yeast, you see, is a catalyst for this reaction.

00:06:58 It causes the decomposition of the hydrogen peroxide, the reaction we wrote on the board, causes that decomposition to take place quickly.

00:07:05 Without the catalyst, hydrogen peroxide will decompose, but only very slowly.

00:07:09 In fact, so slowly that it's hardly, you can't notice no rise in the soap suds.

00:07:17 Before we say anything more about hydrogen peroxide, let's look further at another example of the catalyst working.

00:07:35 Let's put a little hydrogen peroxide in each of these bottles.

00:07:48 Mop up the amount that spilled here to get it out of the way.

00:07:53 This is a chemically resistant top, fortunately.

00:07:56 Otherwise, the hydrogen peroxide would cause the paint to bleach.

00:08:01 Now, in one jar or bottle, I will add one kind of catalyst.

00:08:09 To see the action this time, we'll use a little balloon.

00:08:13 In the second jar, I will add another catalyst, different than the first.

00:08:20 Immediate black coloring showing some reaction has already started.

00:08:27 There are some bubbles forming in this first jar,

00:08:32 but look at the chemical action that's taking place in the second jar.

00:08:36 Much, much faster.

00:08:38 So here we have two catalysts working together.

00:08:43 The first one is a chemical reaction.

00:08:46 The second one is a chemical reaction.

00:08:49 In the second jar, much, much faster.

00:08:52 So here we have two catalysts working to help hydrogen peroxide decompose.

00:09:02 One balloon is already becoming quite inflated.

00:09:05 The other has got a little bit of gas in it, but not much.

00:09:10 What are the catalysts?

00:09:11 In the first case, the catalyst here, the inactive one, is copper sulfate.

00:09:17 This one, which caused all this activity to occur, is ferric chloride.

00:09:22 While both will affect the decomposition of hydrogen peroxide,

00:09:26 it's easy to see that the ferric chloride is much the better one.

00:09:30 It really causes hydrogen peroxide to decompose readily.

00:09:34 Now, this sequence of reactions shows the effect of different catalysts

00:09:40 on the decomposition of hydrogen peroxide.

00:09:42 There are other kinds of chemical reactions which catalysts will affect.

00:09:46 We'll see those in the later part of the show.

00:09:49 But hydrogen peroxide makes a very good one to study

00:09:53 because it has lots of good commercial uses.

00:09:56 I've already mentioned that hydrogen peroxide is used as a bleach.

00:09:59 I have heard that it can be used on the hair of the head as a bleach.

00:10:04 I personally don't particularly care for that use because, to my mind,

00:10:08 hydrogen peroxide is a little bit corrosive,

00:10:10 but some people with care have used it successfully.

00:10:13 It's, however, a very good chemical in the paint industry as a bleach.

00:10:18 It's used in the chemical industry to make different chemicals from others,

00:10:22 starting with hydrogen peroxide.

00:10:25 But one of its most interesting uses is as a rocket propellant.

00:10:29 You probably heard at one time or another

00:10:31 that the Germans developed large-scale rockets during World War II

00:10:36 to use against Britain in the Battle of Britain.

00:10:39 These rockets, the V-2 rockets,

00:10:41 were powered by concentrated hydrogen peroxide as the fuel,

00:10:44 the very same reaction which we illustrated at the start of the show.

00:10:47 By loading these fuel chambers of these rockets

00:10:50 with very concentrated hydrogen peroxide,

00:10:53 what we used here was about 30% hydrogen peroxide.

00:10:56 The fuel value uses 90% or better.

00:11:00 When this decomposed in the presence of special catalysts,

00:11:03 much better catalysts than those we've illustrated,

00:11:06 the reaction is so fast and generates so much heat and power

00:11:09 that the rocket can be made to travel to very high speeds,

00:11:12 upwards of 300 miles per hour.

00:11:17 So that the choice of hydrogen peroxide here

00:11:19 was merely to illustrate the effect of different kinds of catalysts.

00:11:25 Let's go on and see how other reactions can be affected by catalysts.

00:11:31 I just noticed that finally the copper sulfate catalyzed reaction

00:11:34 has gotten around to generating a little bit of oxygen in the bulb.

00:11:38 Of course, this one is long since over.

00:11:40 The hydrogen peroxide has been all decomposed.

00:11:45 Here is yet another reaction which is affected by catalysis.

00:11:48 By the way, catalysis is the word which means using a catalyst.

00:11:58 In each of these bottles I have some hydrochloric acid.

00:12:05 To one of these, I will add some of the same kind of catalyst

00:12:09 that I used in the hydrogen peroxide case, the copper sulfate.

00:12:24 Just swirl it around.

00:12:27 Just swirl this around to shake it a little bit.

00:12:34 Might as well shake this one to show that there is nothing up my sleeve.

00:12:37 The shaking isn't what affects the reaction yet.

00:12:41 To each of these now, I add a little piece of zinc metal.

00:12:48 So-called mossy zinc.

00:12:50 A little piece of zinc metal.

00:12:54 So-called mossy zinc because it's very rough and irregular.

00:13:04 Let's add another piece just to make sure we have a nice chemical reaction.

00:13:09 Some has already started. I'll add one more piece to each.

00:13:15 This is the tube now with the catalyst in it.

00:13:18 This tube has nothing.

00:13:22 Now, in this tube with the catalyst, there are already some bubbles being formed

00:13:27 and rising through the tube.

00:13:29 Here there is some bubble formation around the zinc itself,

00:13:35 but very few of the bubbles are escaping.

00:13:39 Certainly, this reaction has started sooner here than in this case.

00:13:43 The interesting point here is that while copper sulfate was not a very good catalyst

00:13:50 for the decomposition of hydrogen peroxide,

00:13:52 it's a very good catalyst in this reaction.

00:13:54 That is zinc plus hydrochloric acid.

00:13:57 Let's write that one on the board.

00:13:59 Zinc Zn plus HCl gives zinc chloride plus the gas that is seen here, hydrogen.

00:14:23 To balance this reaction for the chemist,

00:14:27 it's necessary to put a two in front of here.

00:14:30 All this says now, in shorthand, this peculiar kind of chemist shorthand,

00:14:35 all this says is that zinc metal reacts with two molecules of hydrochloric acid.

00:14:39 A compound is formed, zinc chloride, which we can't see here but is dissolved in the water.

00:14:44 A gas is given off, hydrogen.

00:14:46 Sometimes you'll see this written with a little arrow here

00:14:49 indicating that the gas, hydrogen, is given off.

00:14:52 There is no set rule on this.

00:14:55 If you wish, you may include the arrow.

00:14:59 Note that the gas bubbles are still rising quickly in the case of the catalyzed reaction

00:15:06 but have not yet come around in the uncatalyzed one.

00:15:12 When writing a chemical reaction in which a catalyst has taken part,

00:15:16 it's sometimes convenient to indicate the catalyst right on the chemical reaction.

00:15:21 In this case, here the iron, Fe, was the material which was the catalyst.

00:15:30 To be very correct, I must write plus three,

00:15:33 showing that it was dissolved iron in the ferric form.

00:15:38 In this case, the catalyst was the copper of the copper sulfate,

00:15:42 so here we write copper plus two, cupric copper.

00:15:50 Let's go on now and look at some other types of catalysis.

00:15:54 We've looked previously at what we would call homogeneous catalysis,

00:15:59 that is, catalysts which are dissolved right in the system.

00:16:02 Well, that was true, except perhaps for the East.

00:16:05 That was, strictly speaking, not a homogeneous catalyst.

00:16:09 Let's go on now and look at something which might rightly be called a type of heterogeneous catalysis,

00:16:15 more than one kind of constituent that you can make out.

00:16:19 I'll catalyze my eyebrows with this flame of the burner.

00:16:50 Get a nice hot flame going.

00:16:57 In the tube, I have a white powder, white crystals.

00:17:03 They are the tube.

00:17:07 From this test tube, there is a delivery tube leading over into a cylinder of water.

00:17:12 Bubbles now that you see are the bubbles coming because

00:17:17 I'm warming the test tube and expanding the air inside of it.

00:17:26 Warm this evenly over all its length.

00:17:36 The formation of the bubbles is slowing down because the air has expanded pretty much as much as it wants to.

00:17:43 Now the solid inside of this test tube, the white solid,

00:17:48 is beginning to melt around the edges where the burner flame is concentrated.

00:17:53 Right there.

00:17:56 Right there.

00:18:11 Slowly melts as the test tube is heated up.

00:18:17 The material in the test tube is potassium chlorate.

00:18:22 Some of you may have performed this experiment.

00:18:25 Potassium chlorate contains oxygen built right into it.

00:18:30 When it decomposes, as it is doing now, indicated by the formation of the bubbles,

00:18:36 when it decomposes, oxygen is liberated, leaving behind potassium chloride.

00:18:42 However, this is a relatively slow reaction.

00:18:45 You see the bubbles are not coming up the cylinder very fast.

00:18:50 Now most of the potassium chlorate is melted.

00:18:53 In this tube here, I have some catalyst.

00:18:58 By inverting the tube upwards, I can slide the catalyst down into the potassium chlorate.

00:19:04 Let's do just that.

00:19:06 There it goes.

00:19:07 Fall right in the bottom.

00:19:08 Fell right in the bottom, rather.

00:19:11 The bubbles stopped for a moment because the burner slipped away from the bottom of the test tube.

00:19:18 Now, there's quite a bit of action going on here.

00:19:23 All the potassium chlorate has melted.

00:19:25 Look at the rapid evolution of bubbles now, much faster than it was before.

00:19:30 The reason that the reaction has speeded up is oxygen is now being liberated more quickly

00:19:36 because of the catalyst that has been added to help the reaction along.

00:19:40 That catalyst is manganese dioxide.

00:19:48 Now, if we were to examine this reaction closely,

00:19:52 let's connect this, by the way, so that no water sucks back into the test tube while this cools.

00:19:58 If we were to examine this reaction closely, let's go about to say,

00:20:01 we'd find that you could find most of the manganese dioxide right back in the test tube

00:20:06 if we did some very careful analysis.

00:20:09 This is one case in which the manganese dioxide hardly changes in form at all,

00:20:14 remains pretty much the same way.

00:20:16 The old-time definition of catalyst used to say that a catalyst is a material

00:20:21 which speeds up a reaction without itself changing, that is, without the catalyst changing.

00:20:26 Strictly speaking, because we understand so little about catalysts,

00:20:29 we can't rightly say that it doesn't change in some way.

00:20:33 Some catalysts that we've studied, there actually is a change.

00:20:38 So potassium chlorate, then, can be decomposed to oxygen much more readily

00:20:42 in the presence of manganese dioxide than it can be in its absence.

00:20:46 So the manganese dioxide is the catalyst.

00:20:50 Now, here's an experiment which will illustrate catalysis, I hope,

00:20:55 which can be performed at home, providing you take care.

00:21:01 Here's our old friend, the candle.

00:21:04 Let me just put this burner out so that that won't cause any reaction

00:21:07 to occur in my coat sleeve, catalyzed or null.

00:21:19 I light my candle.

00:21:24 As soon as the flame gets a little bit higher, I perform the experiment.

00:21:28 Sugar cube, common garden variety sugar cube.

00:21:37 I hold the sugar cube in the flame.

00:21:39 It gets covered with a little soot, first of all.

00:21:47 At the same time, it begins to char, melts.

00:21:50 There's some melting sugar falling.

00:21:53 There, a drop of it just fell.

00:21:54 There's another glob of it melting away.

00:21:57 Caramelizing, this is called.

00:21:59 The sugar caramelizes because of the heat.

00:22:01 There is a smell reminiscent of caramels here.

00:22:08 I'll take another cube.

00:22:10 And because we happen to have some laboratory equipment left over

00:22:15 that wasn't cleaned up, I'll take another cube.

00:22:19 And because we happen to have some laboratory equipment left over

00:22:21 that wasn't cleaned up, we can use this material.

00:22:25 Cigarette ashes.

00:22:27 I'll put a little bit of that on the sugar cube.

00:22:37 Now, with a little bit of care, hoping it stays on,

00:22:41 let's try this experiment now.

00:22:44 Burning the cube where the ashes are placed.

00:22:50 A chunk of ashes just fell off, but the cube is now charring in the same way.

00:23:04 It's getting good and hot.

00:23:06 It's beginning to sputter.

00:23:09 And it's actually burning right now.

00:23:11 The flame is very difficult to see, but if I hold this glowing splint,

00:23:15 it's flickering.

00:23:16 There's some yellow.

00:23:17 The whole cube is burning now.

00:23:18 If I hold this little piece of wood here,

00:23:20 perhaps we can get that to light up just from the burning sugar there.

00:23:24 So.

00:23:28 In the presence of cigarette ashes, the sugar cube will burn.

00:23:31 When the cigarette ashes are absent, the sugar cube just chars.

00:23:34 What is the reason for this?

00:23:36 The reason is catalysis.

00:23:38 There is a material in the cigarette ashes which causes the reaction

00:23:42 to proceed more quickly, so quickly, that it burns.

00:23:45 The reaction to proceed more quickly, so quickly,

00:23:48 that the charring of sugar will reach a burning stage.

00:23:51 That material are metals.

00:23:54 Those materials are metals such as vanadium and chromium,

00:23:57 which are present in the cigarette ashes as a result of being present

00:24:00 in the paper to begin with, of the cigarette, that is.

00:24:03 These are tiny, tiny amounts.

00:24:05 You can barely find them if you look for them, but they're there.

00:24:07 And it only takes a small amount to do the trick.

00:24:10 So that the vanadium and the chromium act as catalysts

00:24:14 for the burning of the sugar.

00:24:16 You see, the sugar itself is a material composed of carbon

00:24:19 and hydrogen and oxygen, and is a fuel,

00:24:22 providing you can get it to burn quickly enough.

00:24:27 If you do this at home, be sure you don't let any of that hot sugar

00:24:30 fall on your finger because your finger will become slightly caramelized,

00:24:34 and you will be catalyzed right out of the region.

00:24:37 Let's look at the next experiment.

00:24:40 ♪

00:24:59 Now, before I get the burner going too high,

00:25:02 I just want to pour a little bit of this liquid in this beaker.

00:25:11 Let's see if I get the right level here.

00:25:17 I think that's about right.

00:25:19 This is a flammable liquid, so I'll hold it away from the burner.

00:25:21 That's about enough.

00:25:23 Now, here's an ordinary penny attached to a copper wire.

00:25:45 I'll get the penny as hot as I can in the burner flame.

00:25:50 It's been blackened from previous heatings,

00:25:53 but now it's turning a little lighter on the outside

00:25:56 of the edges of the penny, rather.

00:25:58 There, now it's getting nice and bright in spots.

00:26:01 Get it good and red hot.

00:26:08 Now, while it's still red hot,

00:26:11 place it over here in this beaker.

00:26:14 Place it over here in this beaker.

00:26:16 Ah, still hot, the wire and all.

00:26:21 The penny is maintaining its red heat,

00:26:24 even though it's away from the burner flame.

00:26:27 The material in the beaker is acetone,

00:26:30 a compound composed of carbon and hydrogen and oxygen.

00:26:34 It's used in paint thinners, fingernail polish remover.

00:26:37 Acetone would burn if it were touched with a flame.

00:26:41 Here is acetone burning, the vapors of acetone burning,

00:26:44 on the surface of the penny, causing the penny to stay red hot.

00:26:48 Now, you see, in the beaker before, the penny was not burning.

00:26:51 The acetone was not burning on the surface of the penny.

00:26:54 So it's because the red hot penny is there

00:26:56 that the reaction can occur.

00:26:58 In short, the penny is the catalyst,

00:27:00 or really, the copper of the penny is the catalyst.

00:27:04 Now, let's put this black box over this,

00:27:07 turn out the lights, and get a good look.

00:27:12 The vapors of acetone, then, are burning on the surface of the penny,

00:27:16 and the penny is maintaining its red heat

00:27:20 because the burning of the vapors is a reaction which liberates heat,

00:27:24 keeping the penny red hot,

00:27:26 and it will stay red hot as long as the acetone lasts.

00:27:29 This is an example of the same kind of catalysis

00:27:32 that is used in making high-octane gasoline from petroleum.

00:27:36 There, other metals are used as catalysts

00:27:39 so that you can break down, crack, that is,

00:27:42 large molecules of petroleum into small ones,

00:27:45 the high-octane gasoline.

00:27:47 Well, what have we seen here so far, then?

00:27:49 We've talked about those mysterious secret agents of chemistry,

00:27:53 the catalysts, materials which speed up chemical reactions.

00:27:58 We looked at hydrogen peroxide

00:28:01 and how it decomposed in the presence of yeast and soap suds,

00:28:04 causing a lot of soap suds to form.

00:28:08 We then looked at zinc decomposing in hydrochloric acid.

00:28:12 For these, we wrote chemical reactions.

00:28:15 Finally, we generated oxygen from potassium chlorate

00:28:19 using manganese dioxide,

00:28:21 and our last bit, the penny,

00:28:24 which was catalyzed by the acetone vapors.

00:28:29 There it is, still red hot.

00:28:32 Thank you.

00:29:02 This is National Educational Television.