00:00:01 I am Bassam Shakhashiri from the National Science Foundation.

00:00:05 You'll have to forgive my hoarse voice. I've been suffering from a head cold for the past three and a half days.

00:00:11 As my colleagues at the National Science Foundation will attest, I haven't been to work for three and a half days,

00:00:16 so I made a special point of coming out of bed to do this tonight.

00:00:20 I hope you'll bear with me as we go through some of the experiments tonight.

00:00:26 I promise you a great deal of fun, and I hope you will learn as we go along doing a variety of special experiments

00:00:36 in the tradition of a great scientist, Michael Faraday.

00:00:40 I think everyone who has come into the auditorium has received a copy of the green pamphlet.

00:00:47 I'd like you to read this, not now if you haven't read it yet.

00:00:51 I'd like to also point out to you how important it is for each one of you to pay very close attention to what's going to happen.

00:01:00 Because in science, a great deal happens, sometimes very fast, and if you're not very attentive, you'll miss it.

00:01:08 So I want you to be very, very attentive, and if you need some help, you can always call on your mommy to come and help you.

00:01:16 Seriously, I want you to be as attentive as possible, to pay special attention to color changes, to smoke, to noise,

00:01:27 to a variety of things that might happen, and try to make as many observations as you possibly can,

00:01:33 and try to make some sense out of these observations.

00:01:37 Before I go any further, I just would like to make a special tribute to the National Academy of Sciences

00:01:45 for hosting this special occasion for the second year in a row.

00:01:50 I don't know if Dr. Press is in the audience.

00:01:54 Frank, could you come up here for a minute, please?

00:01:56 Yes, you.

00:01:59 Thank you.

00:02:11 This is Dr. Frank Press, the president of the National Academy of Sciences.

00:02:15 Frank, it's my pleasure to present to you and to the Academy volume one of my chemical demonstrations series,

00:02:23 and volume two, just hot off the press.

00:02:26 Terrific.

00:02:27 And I'd like to, if I may, read the dedication.

00:02:31 In both volumes it says,

00:02:33 The Frank Press and the National Academy of Sciences with appreciation for continued support to science education.

00:02:39 Sam Shakashiri, December 19, 1985.

00:02:42 Well, thank you, Sam, very much.

00:02:44 Thank you, Frank.

00:02:47 Thank you.

00:02:55 Now I'd like you to sit back and relax and try to enjoy what is about to happen.

00:03:02 I want you, as I said, to be very attentive

00:03:05 and to make sure that whenever we do experiments in science,

00:03:09 we observe and obey the safety regulations.

00:03:14 And I want you to know that I'll have my eye protection on throughout the evening as I do experiments.

00:03:20 And I'd like you also to see the fire extinguisher that I have available here,

00:03:25 just in case an accident happens.

00:03:28 I hope no accidents happen this evening,

00:03:32 but if they do, we are prepared to deal with them.

00:03:37 I'd like to talk to you a little bit about chemicals,

00:03:41 because chemicals are all around us.

00:03:44 The food that we eat is made up of chemicals.

00:03:47 The air that we breathe is a mixture of chemicals.

00:03:51 The medicine that we take when we're sick is nothing but chemicals.

00:03:55 Our own bodies are made up of chemicals.

00:03:57 What goes on inside our bodies, inside all the organs in our bodies,

00:04:02 is nothing but a set of chemical reactions, biochemical reactions.

00:04:06 And so it's extremely important for us to understand

00:04:09 the properties and the behavior of a variety of chemicals,

00:04:13 so that we can enjoy the benefits of these chemicals,

00:04:17 as well as be aware of their potential hazard.

00:04:21 We should be very, very careful in handling all chemicals,

00:04:24 and you'll notice this evening, and every time anybody does experiments,

00:04:28 we should be carefully obeying the safety regulations.

00:04:32 I'd like to, in keeping with what I just said,

00:04:36 point out that there are quite a few chemicals that we deal with.

00:04:39 Here's a carton of milk.

00:04:42 Here's a can of Coke and some 7-Up,

00:04:45 and a variety of other chemicals that can be readily found around the house.

00:04:52 And these chemicals have different properties.

00:04:55 One of the themes that we are going to deal with tonight

00:04:58 is the so-called acid-base property of substances.

00:05:03 So we're going to be looking at the behavior of some substances,

00:05:08 their acidic properties, or their basic properties.

00:05:11 Now everybody has heard about the pH scale.

00:05:14 You see television advertisement dealing with the pH of shampoo,

00:05:17 or the pH of different substances.

00:05:21 And pH is nothing but a measure of how acid, or how basic,

00:05:28 is a substance.

00:05:30 And there are a number of take-home experiments

00:05:34 that I'll tell you about later,

00:05:36 that I'd like you to think about doing,

00:05:39 in terms of looking at the acid-base properties of these chemicals.

00:05:45 It turns out that there is a way,

00:05:52 there are several ways actually,

00:05:53 in which we can test whether a substance is an acid or a base.

00:05:57 You've all heard of the acid test.

00:05:59 You've all heard of the litmus test.

00:06:01 What I have here are two pieces of litmus paper.

00:06:04 If you just look at the monitor,

00:06:06 you can see that they are of different colors.

00:06:10 One is blue litmus paper,

00:06:12 and the other one is a so-called pink or red litmus paper.

00:06:17 The blue litmus paper,

00:06:20 which is in my right hand,

00:06:22 this will turn red if the substance that we are trying to test is an acid.

00:06:29 And this pink or red litmus paper will turn blue

00:06:33 if the substance that we're trying to test is a base.

00:06:37 And the one thing that we want to try to do to begin with

00:06:40 is test whether milk is an acid or a base.

00:06:46 So we take some milk out,

00:06:48 and what we need to do is test with this paper.

00:06:58 What I do is you just watch what I'll do here.

00:07:01 I'll take a drop and put it on the litmus paper to wet the paper.

00:07:08 Is there a change in color?

00:07:11 Can you see any change take place?

00:07:14 Well, you have to be careful, you see,

00:07:16 because sometimes you think you see a change as the paper becomes wet.

00:07:22 So you have to distinguish the wetness of the paper from a color change.

00:07:27 Let's take the other paper and put some milk on it too.

00:07:36 Is there a change there?

00:07:38 It's pretty hard to tell.

00:07:39 You see that on the monitor, but it's much more easily the case

00:07:43 if you look at this up close.

00:07:45 And this is one of the experiments that I will give you

00:07:48 some more instructions about doing at home.

00:07:51 You'll be able to tell whether the milk is an acid or is a base.

00:07:57 You can do the same thing with a variety of different chemicals

00:08:02 that you can find at home,

00:08:04 and you have to be very careful not to mix the chemicals

00:08:08 that are edible with those that are not edible.

00:08:11 For example, here's some, what's this, household ammonia,

00:08:16 and you've got to be careful not to mix those.

00:08:21 We'll take some ammonia, we'll set it up here,

00:08:25 and we'll go to see if we can find some more litmus paper

00:08:32 to apply the acid test.

00:08:37 And once again, we get two pieces of paper.

00:08:42 I'll just set them aside like so over here.

00:08:54 I want you to see I'm just drying this,

00:08:57 and I want to use the other end.

00:09:00 So I take a little bit of the ammonia,

00:09:02 and I take this paper and I touch it.

00:09:06 Is there a change in color?

00:09:08 Yes, what's the color change that you see?

00:09:12 So the litmus paper turned blue or violet, right?

00:09:16 And that tells us that the ammonia is a base

00:09:20 because this pink or red litmus paper,

00:09:23 when it turns blue, that means the substance is a base.

00:09:26 Let me show you the same thing with the other piece of litmus paper.

00:09:32 And you see this one simply gets wet.

00:09:35 Well, this is the kind of experiment that you ought to try to do at home.

00:09:39 I'll give you some more instructions about doing that at home.

00:09:43 There are other ways in which we can measure the acidity

00:09:46 or the basicity of a substance.

00:09:48 There is something called pH paper,

00:09:50 and I have samples of pH paper over here.

00:09:53 I'd like to show you a close-up of that.

00:09:55 You see there's different colors that this paper will turn

00:09:59 depending on the pH of the liquid or the solution that we're dealing with.

00:10:05 And if you have access to such paper in school

00:10:08 or your teacher can provide you with some,

00:10:11 you might as well do the experiment with the pH paper

00:10:14 because that will then tell you the exact acidity or basicity

00:10:18 of the liquid that you are dealing with.

00:10:21 There's still a more sophisticated way of measuring pH,

00:10:27 and this way is a so-called electrochemical method.

00:10:31 It uses an electrode,

00:10:33 and what you do is you dip the electrode in the liquid that you want to measure,

00:10:39 and you hook it up to a meter,

00:10:41 such as the one that you see over here.

00:10:45 And it's not on.

00:10:48 Is that on now?

00:10:50 Okay.

00:10:52 What you try to do then is to measure the pH value of the liquid.

00:11:00 Now I have to tell you that there is something mechanically wrong

00:11:04 with this device that I'm using

00:11:06 because the pH of the liquid that I have in this beaker

00:11:12 should be close to 7.

00:11:14 It should be about 6.5, 6.52, 6.53.

00:11:19 Actually, it reads 16.53.

00:11:23 The one is erroneous,

00:11:25 and that's on my display right in front of me here.

00:11:29 The one is flashing, indicating that something is wrong,

00:11:32 and that's why I can't show you the actual pH values of these different liquids.

00:11:36 However, because in science we like to do experiments,

00:11:40 I'm going to do this as an experiment

00:11:43 and find out if we can,

00:11:45 if this device is simply off

00:11:48 in the one decimal place that we're talking about here.

00:11:52 So I'm going to take this milk

00:11:55 and try this.

00:12:00 Turn this off.

00:12:05 What's it reading now?

00:12:07 It's even worse, right?

00:12:10 That should be a 6 point something or other.

00:12:14 Something is drastically wrong here.

00:12:17 So we can't rely on this measurement,

00:12:20 but we will take this,

00:12:25 and where did we have the ammonia?

00:12:27 Which one was the ammonia?

00:12:28 This was the ammonia, right?

00:12:30 Let's see what the ammonia does.

00:12:32 If I take the electrode,

00:12:34 put this on standby,

00:12:38 turn this.

00:12:41 So this demonstrates,

00:12:43 we know that the ammonia is basic.

00:12:45 This demonstrates that this device is not working very well,

00:12:49 and therefore we shall turn it off

00:12:52 and move on to do something else.

00:12:57 There are a variety of items in the home that you can test

00:13:01 to find out if they're acidic or basic.

00:13:04 It turns out that most of the household items

00:13:08 that we can consume, that we can eat,

00:13:10 most of them, not all of them,

00:13:12 most of them are acidic.

00:13:15 And the ones that we don't eat are basic.

00:13:20 Not all of them, but most of them.

00:13:22 And this is the kind of experiment

00:13:24 you should be able to try to do at home.

00:13:28 You know, there are many, many, many things that we eat

00:13:31 that are not acidic.

00:13:32 For example, when you have,

00:13:34 when you take an antacid,

00:13:36 obviously you're taking something

00:13:38 that will counteract the acid.

00:13:41 And so if you take milk of magnesia, for example,

00:13:43 you will be taking something

00:13:45 that will counter the effect of the acid

00:13:47 and it will be basic.

00:13:49 So that would be one of the kinds of things

00:13:51 that you might test the pH for at home.

00:13:54 Now there are ways in which we can tell,

00:13:58 additional ways in which we can tell

00:14:00 that a reaction is an acid reaction or a basic reaction.

00:14:04 And that is by using a different set of color changes.

00:14:09 Litmus is one type of indicator.

00:14:12 And what I have at the lecture table over here

00:14:15 is a set of different acid-base indicators.

00:14:20 And the way in which we can tell

00:14:21 that a reaction is taking place,

00:14:23 if indeed it is an acid-base reaction,

00:14:26 is to see if there is any color change.

00:14:29 I've arranged these different cylinders and beakers

00:14:33 in such a way that the cylinder on my right

00:14:37 with the beaker to its immediate left

00:14:40 has the same liquid in it.

00:14:42 So we'll use the color of what's in the beaker

00:14:44 as the reference point always in the pair.

00:14:48 And what I will try to do now

00:14:50 is handle a very cold chemical.

00:14:56 This chemical is solid carbon dioxide.

00:14:59 I'll put some over here.

00:15:00 You can look at it on the monitor.

00:15:04 This is dry ice, which is solid carbon dioxide.

00:15:08 And it has the property of changing directly

00:15:11 from a solid to a gas.

00:15:13 That property we call sublimation.

00:15:16 It just undergoes this direct change

00:15:19 which we call sublimation.

00:15:21 But carbon dioxide, when it reacts with water,

00:15:24 produces an acidic substance.

00:15:28 So we're going to take chunks of dry ice,

00:15:30 and I'm wearing, by the way, this glove

00:15:32 to protect my hand from this very cold carbon dioxide.

00:15:36 The temperature of carbon dioxide

00:15:38 is minus 78 degrees Celsius.

00:15:41 In science, we keep track of temperature

00:15:44 on the Celsius scale.

00:15:46 And the sublimation point of carbon dioxide

00:15:49 is minus 78 degrees Celsius.

00:15:52 So I'm going to take a chunk of dry ice

00:15:54 and drop it in here.

00:15:55 We'll see what happens.

00:15:57 Lots of interesting things begin to happen.

00:16:01 We'll drop some more here.

00:16:13 You see any changes take place?

00:16:17 The color has changed.

00:16:19 Look at this color changing over here.

00:16:35 These are different acid-base indicators,

00:16:39 different than litmus.

00:16:41 And they change color as the carbon dioxide

00:16:45 reacts with the liquid that's in each of the cylinders.

00:16:48 And the color change depends on what's in each cylinder.

00:16:53 The same thing would happen if I were to put the dry ice

00:16:56 in each of these beakers.

00:16:58 But remember, we left the beakers to tell us

00:17:00 the original color of the liquid that we had in there.

00:17:04 So carbon dioxide reacts with water

00:17:07 to give us an acidic solution.

00:17:10 And carbonated beverages have a great deal

00:17:13 of dissolved carbon dioxide in them.

00:17:15 I'm going to try to show you how much carbon dioxide

00:17:19 there is in a typical can of 7-Up.

00:17:23 So what I'm going to do is take this baby bottle.

00:17:26 And this baby bottle has been fitted

00:17:29 with a very special cap that has a hole in it.

00:17:33 Through this hole I've put a medicine dropper,

00:17:37 the rubber bulb of a medicine dropper.

00:17:39 And I'll show you that this is a very hard

00:17:44 piece of rubber.

00:17:46 I'll take it out and try to blow it up.

00:17:52 You see I can't blow it up.

00:17:56 It's very, very hard.

00:17:58 I'll put it back in.

00:18:02 And what I'll do is open this can of 7-Up.

00:18:07 Did you hear that noise?

00:18:08 You've all heard that noise, right?

00:18:10 That's the carbon dioxide escaping.

00:18:12 I'll put this in the baby bottle.

00:18:20 And the next thing I'm going to do

00:18:23 is close this off very tightly

00:18:27 and then shake it up a little bit.

00:18:30 And you begin to see what's happening

00:18:34 to this rubber ball

00:18:37 The carbon dioxide comes out of the 7-Up.

00:18:42 The pressure of carbon dioxide that's dissolved

00:18:45 in the contents of the 7-Up can is relatively high.

00:18:49 And you can see I couldn't blow it out

00:18:51 but here's the effect of just a little bit of 7-Up

00:18:57 in that baby bottle.

00:19:03 Now let's do a couple of other experiments.

00:19:06 Once in a while you might want to look back here

00:19:08 and see if there's any further color change.

00:19:10 It's a very colorful kind of an experiment.

00:19:13 Here's another experiment that you might want to do at home.

00:19:17 Actually, this is such an easy experiment.

00:19:19 All of these experiments are easy

00:19:21 if you know what you're doing.

00:19:23 And you always have to be paying close attention

00:19:27 to the person who is helping you do those experiments.

00:19:31 In that regard, I'd like to get a volunteer from the audience.

00:19:36 I see I have too many volunteers.

00:19:38 I'll tell you what.

00:19:39 There is a person who at one time

00:19:42 indicated that she would like to help out

00:19:44 in doing these experiments.

00:19:46 I'd like to call on Jan Watson to come and help me.

00:19:49 Jan, want to come out and help?

00:19:53 Come on up here.

00:19:55 No, you're not too old.

00:20:02 This is a very simple experiment that Jan will help out with.

00:20:06 Here's a pair of goggles for you.

00:20:09 What we're going to do is take some baking soda.

00:20:15 We open the baking soda

00:20:17 and we'll just add a little bit of baking soda in there.

00:20:21 We're measuring this very carefully.

00:20:23 You can see that.

00:20:24 Next thing I'd like you to do is take this and stir it up.

00:20:27 See what happens when you stir it up.

00:20:32 Don't be afraid. Just stir it up.

00:20:36 You see the baking soda, which has been added to the water.

00:20:39 What's happening to it?

00:20:41 What's happening to it, Jan?

00:20:42 Dissolved.

00:20:43 Is it a clear solution?

00:20:46 I don't know if my glasses are.

00:20:51 We can look at the TV monitor over there and see.

00:20:54 Is it clear?

00:20:55 No.

00:20:56 It's not clear yet.

00:20:58 Keep stirring and see what happens.

00:21:00 The next thing that we're going to do is take some spaghetti.

00:21:07 This is something you can find at home.

00:21:09 You take the spaghetti and you break the spaghetti into small pieces,

00:21:14 about two and a half centimeters.

00:21:16 How many inches is that?

00:21:18 Two and a half centimeters, like so.

00:21:21 Is it clear now, Jan?

00:21:24 Sort of.

00:21:25 Sort of, she says.

00:21:26 Very good.

00:21:28 Now the next thing I'd like you to do is take these pieces of spaghetti

00:21:31 and drop them into the beaker.

00:21:35 All of them?

00:21:36 All of them, yeah.

00:21:37 Be careful not to bump this because this might just blow up.

00:21:42 Now we've put the spaghetti in the beaker.

00:21:44 What happens to the spaghetti that has been added to the beaker

00:21:47 that has in it the dissolved baking soda?

00:21:51 It's clear.

00:21:53 The liquid is clear, but where is the spaghetti?

00:21:55 On the bottom.

00:21:56 Can you hear what she's saying?

00:21:58 Yes.

00:21:59 Brilliant.

00:22:00 The spaghetti is on the bottom.

00:22:01 So what does that tell us about the density of the spaghetti

00:22:05 compared to that of the liquid?

00:22:06 Is it heavier or lighter?

00:22:07 Heavier.

00:22:08 It's heavier, right?

00:22:09 All right.

00:22:10 The next thing we're going to do, she's going to do,

00:22:12 is to take some vinegar.

00:22:14 You've handled that before.

00:22:16 We'll open this.

00:22:18 What I'd like you to do is add some vinegar very slowly to the beaker

00:22:22 and see what happens.

00:22:27 Okay, that's good.

00:22:29 Now what do you see happening?

00:22:31 Spaghetti is rising.

00:22:34 Spaghetti is rising, she says.

00:22:35 Okay, what else is happening?

00:22:37 The water is bubbling.

00:22:38 And there are bubbles in the liquid, right?

00:22:41 Uh-huh.

00:22:42 So let's just watch and see if anything beyond this happens.

00:22:47 What happens if I stir this up a little bit more?

00:22:52 The vinegar reacts with the dissolved baking soda

00:22:57 and it releases a gas.

00:22:59 These gas bubbles that you see are carbon dioxide bubbles.

00:23:03 And if you look very carefully near the bottom of the beaker,

00:23:09 you can see, let me take this out of your way here,

00:23:11 you can see it on the TV much better,

00:23:13 you can see the spaghetti strands, can you?

00:23:16 Not that easily, right?

00:23:20 Well, let's add a little bit more.

00:23:21 Is it okay to add a little bit more?

00:23:23 All right.

00:23:24 She says it's okay.

00:23:25 We'll add more.

00:23:28 And we'll let this experiment go for a little bit

00:23:32 and see if anything happens to the spaghetti that is at the bottom.

00:23:37 You can see some of the spaghetti beginning to stand up, right?

00:23:43 Oops, I keep pushing this thing in the way.

00:23:46 All right.

00:23:47 So let's see what else we can do with carbon dioxide.

00:23:54 And what I'll do is I'll bring in this.

00:24:06 This is how some of us wash dishes at home, right?

00:24:10 What we're going to do, Jan, is ask you to put this glove on

00:24:18 and take some of the dry ice and simply put them in there.

00:24:22 See what happens.

00:24:25 It's pretty hard to pick them up.

00:24:27 Just dump it in there.

00:24:30 Dump some more.

00:24:33 Tell you what.

00:24:34 Why don't you just take this whole thing and dump a few in there, okay?

00:24:37 That will be easier.

00:24:39 Okay.

00:24:40 That's good.

00:24:41 Thank you.

00:24:46 Now can you blow on it a little bit?

00:24:50 Just blow on it, blow on it.

00:24:53 Like Macbeth.

00:24:54 Like Macbeth, right.

00:24:59 What this is is condensed water vapor.

00:25:03 What I had in the trough, I had some water, some warm water.

00:25:07 We simply put some dry ice on top of it,

00:25:09 the same kind of experiment we did over there,

00:25:11 except that the water was warm.

00:25:13 And what you see is the condensation of water vapor

00:25:16 on the carbon dioxide that's escaping to the atmosphere.

00:25:20 And this is one of the ways in which they make smoke sometimes in the movie.

00:25:26 Well, thank you very much for helping out.

00:25:28 Give her a hand for helping me out.

00:25:31 It wasn't so bad, was it?

00:25:35 Okay.

00:25:37 Now what I'd like to do is move over to a different kind of experiment,

00:25:48 an experiment that deals with this reaction.

00:25:52 Everybody's carried out this reaction at one time or another.

00:25:55 You take a match and you strike it.

00:25:57 It's no big deal, right?

00:25:58 Actually, it is a big deal

00:25:59 because there's a lot of chemical change taking place there.

00:26:03 There is heat released.

00:26:05 There's energy in the form of heat.

00:26:06 There's energy in the form of light.

00:26:09 And the match is burning very fast.

00:26:12 In fact, if I don't blow it out very quickly, I'll burn myself, right?

00:26:16 So this process that we're dealing with here is called combustion.

00:26:22 This is an example of what we refer to as controlled combustion.

00:26:27 When a combustion process goes out of control,

00:26:30 then we have what we refer to as a very fast reaction.

00:26:34 We call it an explosion.

00:26:36 What I'd like to show you now is the way in which we can use

00:26:42 a different source of energy, namely a propane tank,

00:26:48 to carry out a combustion process using a burner.

00:27:00 Here's another example of controlled combustion.

00:27:05 Oh!

00:27:07 Very good!

00:27:10 Very good!

00:27:13 Very good!

00:27:16 Very good!

00:27:17 Applause

00:27:24 I'm going to give you a surprise talk of the series.

00:27:27 That's me.

00:27:28 Is that young man?

00:27:29 I am he.

00:27:30 And have you been a good boy this year?

00:27:32 I think so.

00:27:33 Well, good.

00:27:34 I'm glad to hear that.

00:27:35 We have to ask Mr. Block.

00:27:37 Is Mr. Block here?

00:27:40 The next question I have for you,

00:27:42 have all these boys and girls come to learn some science from you?

00:27:47 I hope so.

00:27:48 Well, I am so pleased about that,

00:27:51 that I have brought some presents for them and for you.

00:27:55 Now let me see.

00:27:57 It's down here in my sack.

00:28:01 Yes.

00:28:04 There it is.

00:28:06 I have an envelope here.

00:28:08 Uh-oh.

00:28:09 It has in it some litmus paper.

00:28:12 Oh, good.

00:28:13 Now, I didn't bring you any electrical pH meters

00:28:17 because I understand they don't always work.

00:28:19 That's right.

00:28:20 Laughter

00:28:22 But I did bring you some old reliable litmus paper

00:28:25 and some other things.

00:28:26 Perhaps you will.

00:28:28 And I have an envelope like that for each of your visitors here this evening.

00:28:32 Oh, that's very kind of you, Santa.

00:28:34 And I wish to each of you a very Merry Christmas.

00:28:38 Thank you very much.

00:28:39 And the same to you, Santa.

00:28:40 Thank you.

00:28:41 Thank you.

00:28:42 Applause

00:28:48 Can you stay, Santa, and watch the rest of this?

00:28:51 Okay, sure.

00:28:54 Let's take a look and see what's in Santa's bag in here.

00:29:01 Well, I see...

00:29:05 I'll just put what's in there.

00:29:06 I see lots of pieces of litmus paper for you to work with.

00:29:11 I also see a button that everybody can get.

00:29:16 Can you read that?

00:29:17 All right, just like the button I have.

00:29:20 I also see a very small disk.

00:29:25 I don't think you can read that on the camera,

00:29:27 but I'll tell you what it says.

00:29:29 It says, discover excitement, jump into science.

00:29:34 That should give you a clue as to what this disk will do.

00:29:38 There's a set of instructions for using this disk.

00:29:42 The heading on the instructions is jumping disk.

00:29:47 So that's a clue for you.

00:29:51 There are two pieces, two dark pieces of polarizers.

00:29:57 I'll tell you about those a little bit later.

00:29:59 Santa anticipated one of the experiments I'm going to do.

00:30:04 And then there is a light stick for everybody to do experiments with

00:30:11 and a set of instructions to work with the light stick.

00:30:17 And finally, there is...

00:30:20 This is the part you have to pay very close attention to.

00:30:23 There is a blank gummed label.

00:30:28 This blank gummed label is for you to write your name and address

00:30:35 and send it to me so I can send you a full set of instructions

00:30:40 for doing many of the experiments that we're doing here today free of charge.

00:30:47 All you have to do is write your name and your mailing address on this gummed label

00:30:53 and send it to me to the National Science Foundation.

00:30:56 And in a couple of weeks, right after the Christmas rush,

00:30:59 we'll give you a set of instructions for doing some of these other experiments

00:31:04 that we've talked about.

00:31:06 Okay, so as you leave today, tonight,

00:31:09 each one of you from Santa and from Santa's helpers

00:31:13 will be getting one of those envelopes.

00:31:15 Is that right, Santa?

00:31:16 That's right.

00:31:17 Okay.

00:31:18 So let's move on with this experiment that we were trying to do over here.

00:31:22 This experiment, it deals with combustion.

00:31:25 This is the combustion of propane,

00:31:28 and it releases energy in a lot of different forms,

00:31:31 heat being one of them.

00:31:33 And the other one, of course, is the emission of light.

00:31:37 We're going to try to use this source of heat to heat up this can.

00:31:43 Now, what I'd like you to do is to listen very carefully

00:31:46 to what might be inside this can.

00:31:50 Do you hear anything?

00:31:52 There's a liquid sloshing around, right?

00:31:55 What we're going to do is heat this liquid.

00:31:59 I'll tell you, this liquid is water,

00:32:01 and we're going to heat this.

00:32:07 And how do we know that water boils?

00:32:12 What do we look for?

00:32:14 We look for bubbles,

00:32:16 but it's pretty hard to see bubbles inside this can, right?

00:32:19 What do we look for?

00:32:21 Well, you know, we look for steam,

00:32:23 but actually what we see is not steam

00:32:26 because steam is an invisible gas.

00:32:29 What we see is condensed water vapor,

00:32:32 and so that's what we ought to try to look for near the top of this can.

00:32:36 There's an opening over here.

00:32:38 I'll show it to you without burning myself.

00:32:42 There's an opening right there,

00:32:44 and we'll watch to see if any condensed water vapor

00:32:48 comes out of that can.

00:32:51 Make sure this is sturdy.

00:32:55 Okay, let's take a look back at the spaghetti

00:32:59 that Mrs. Watson was helping us with,

00:33:02 and I don't see too much happening to this spaghetti.

00:33:07 Shake them up a little bit.

00:33:16 And we'll see what happens, if anything happens.

00:33:20 That's why we do experiments,

00:33:22 to find out if anything is in fact taking place.

00:33:25 We look for changes, as I told you, in color

00:33:28 and in other properties that we are dealing with.

00:33:34 Now, I told you one of the themes that we're dealing with

00:33:38 is acid-base chemistry.

00:33:42 Now what I'd like to do is carry out

00:33:45 a different kind of an experiment,

00:33:47 which indeed is an experiment.

00:33:49 See if it works out.

00:33:51 In this experiment, I'm going to do on the top of this

00:33:57 a piece of cardboard right here,

00:33:59 and what I'm going to do is take a couple of crystals

00:34:05 of a solid, just put them on top.

00:34:14 And the next thing I'm going to do is

00:34:17 take this liquid out of this flask

00:34:21 and pour it on top of this cardboard

00:34:24 where the crystals of this solid are,

00:34:26 and we'll see what happens, if anything happens.

00:35:18 You see, we changed the liquid that was inside this flask

00:35:22 into this crystalline form.

00:35:25 What this is, was a super-saturated solution

00:35:29 of a substance we call sodium acetate,

00:35:32 and it crystallizes in this form

00:35:35 the minute that you put a seed of crystal sodium acetate in it.

00:35:40 That's what I took out of this bottle,

00:35:42 and that's how we can do this experiment.

00:35:44 If I had a steadier hand,

00:35:46 we could have made a much longer column out of this.

00:35:49 And by the way, this can be reused

00:35:53 by putting it back into a clean beaker and heating it,

00:35:56 not adding any liquid to it,

00:35:58 just heating it until it dissolves again

00:36:01 in its own water of crystallization.

00:36:04 So this is sodium acetate trihydrate.

00:36:07 Let's take a look at the can.

00:36:09 You see anything coming out of the can?

00:36:11 What do you see coming out of the can?

00:36:14 It's condensed water vapor, right?

00:36:17 You can't see steam.

00:36:19 So this can is getting pretty warm now,

00:36:22 and what I'm going to try to do

00:36:25 is take the can,

00:36:30 and I'm going to stopper it

00:36:32 using this rubber stopper, like so.

00:36:44 I'll take it off,

00:36:46 put the rubber stopper on,

00:36:50 and put this in some ordinary ice,

00:36:53 just ordinary ice.

00:36:55 Just watch the camera,

00:36:57 and cool it down.

00:37:03 Okay, now I'm going to take the can

00:37:05 and I'm going to cool it down.

00:37:07 I'm going to take the can

00:37:09 and I'm going to cool it down.

00:37:12 Ow!

00:37:14 You can see what's happening to the can.

00:37:21 The can is collapsing.

00:37:30 The can has collapsed

00:37:32 once I put this stopper on.

00:37:34 And the question is,

00:37:36 how come the can collapsed

00:37:38 once I put the stopper on?

00:37:40 Because I pushed it?

00:37:47 Very good.

00:37:53 I'll tell you what,

00:37:55 I'll try to push it some more

00:37:57 and see if I can make it collapse, okay?

00:38:01 And I'm pushing pretty hard on it.

00:38:03 I can't make it collapse

00:38:05 as much as it has collapsed so far.

00:38:07 So I didn't push it,

00:38:09 something else pushed it, right?

00:38:11 Who did?

00:38:13 Who pushed it?

00:38:15 Some invisible giant of some sort?

00:38:19 Right?

00:38:21 Let's stop and think of what happened

00:38:23 to this can.

00:38:24 We had a little bit of water in it,

00:38:26 and we heated the water,

00:38:28 and the water came out of the opening, right?

00:38:30 When the water was coming,

00:38:32 water vapor was coming out of the opening,

00:38:34 it was sweeping along with it

00:38:36 some of the air that was inside the can.

00:38:38 When I put the rubber stopper on the can

00:38:42 and closed it off,

00:38:44 and then cooled it back down

00:38:46 to close to room temperature,

00:38:48 then the can collapsed.

00:38:51 The conclusion that we come to

00:38:54 is that the pressure inside the can

00:38:57 was different than the pressure outside the can.

00:38:59 Right?

00:39:01 And where is the pressure higher,

00:39:03 outside the can or inside the can?

00:39:05 Outside the can.

00:39:07 How did the pressure inside the can get to be smaller?

00:39:09 It got smaller because some of the air molecules

00:39:13 that were inside the can

00:39:15 were swept along with the water vapor

00:39:17 when it was escaping.

00:39:19 And so this is the experiment of the collapsing can

00:39:22 that shows us that the pressure of the atmosphere,

00:39:26 atmospheric pressure,

00:39:28 is a very real pressure

00:39:31 and a very strong pressure.

00:39:34 And now what I want to try to do

00:39:36 is to change this burner

00:39:40 and go to this burner

00:39:44 and see what happens

00:39:55 as we carry out another

00:39:58 controlled combustion experiment.

00:40:04 Again, using propane as our fuel.

00:40:09 And you see now this,

00:40:12 you see this flame is different in color

00:40:15 than the flame that we had in this burner.

00:40:17 And one of the questions we should think about is

00:40:20 how come the color of this flame

00:40:23 is different than the color of that flame?

00:40:25 Is there any significance to the difference in the color?

00:40:28 Those are the kinds of questions

00:40:30 that we always try to think about answering

00:40:32 when we do scientific experiments.

00:40:34 Let's increase the flow of the gas.

00:40:38 And you see no matter how much I increase the flow

00:40:41 in this burner,

00:40:43 the color of the flame remains yellow.

00:40:47 Now what we've learned so far, I hope,

00:40:50 is that some substances

00:40:53 undergo controlled combustion.

00:40:56 There are many substances that do not undergo combustion.

00:40:59 They don't burn.

00:41:00 Combustion means they combine with oxygen

00:41:03 and give off energy in the form of heat,

00:41:05 in the form of light.

00:41:07 Now when you came into the auditorium tonight,

00:41:10 you saw lots of different things on the table

00:41:12 including those balloons that are up in the air.

00:41:16 I hope you noticed that these balloons are up in the air

00:41:18 and they are on strings.

00:41:20 So the strings are holding the balloons

00:41:23 from floating farther up into the auditorium.

00:41:28 What does that tell us about the gas

00:41:30 that's inside each of these balloons?

00:41:33 What?

00:41:34 It's helium?

00:41:36 You think it's helium?

00:41:38 Well, I'll tell you.

00:41:40 Helium is a gas.

00:41:43 That's correct.

00:41:44 It's also a gas which is lighter than air,

00:41:48 which means that when you fill up a balloon

00:41:50 with helium gas,

00:41:51 the balloon will go up in the air.

00:41:54 But helium happens to be a gas

00:41:56 which does not undergo combustion.

00:41:59 It means it doesn't burn.

00:42:01 So one way of finding out what's inside these balloons

00:42:04 is to put this flame right to the balloon

00:42:07 and see if there is a combustion reaction.

00:42:10 All right?

00:42:11 You ready?

00:42:12 Let's do that.

00:42:13 Let's take this flame and put it right to this balloon.

00:42:18 And you see what happened?

00:42:19 What happened?

00:42:22 The balloon popped.

00:42:23 Some of you were not paying close attention,

00:42:26 and that's why we are going to repeat this experiment

00:42:31 using this other balloon.

00:42:33 That's what we do in science.

00:42:34 We repeat the experiment over and over and over,

00:42:37 not only twice,

00:42:38 but enough times to convince ourselves

00:42:41 that the experiment observations are valid.

00:42:44 So let's go and do this,

00:42:45 being careful not to put the flame to the string

00:42:48 because if you put the flame to the string,

00:42:50 what will happen to the balloon?

00:42:53 How do you know that?

00:42:56 Well, if indeed it has helium in it,

00:43:00 see, I can put this torch,

00:43:02 this flame to the string,

00:43:04 and what will happen?

00:43:07 How do we get to find out?

00:43:10 Well, you see, when you do experiments,

00:43:11 you have to decide which experiment you want to do.

00:43:16 If you want to find out

00:43:18 if the flame will burn the thread,

00:43:21 you can do that experiment.

00:43:22 I don't want to find that out.

00:43:23 I want to find out what will happen up here.

00:43:26 See, and the flame went out.

00:43:29 So very quickly, we go like so.

00:43:36 And indeed, the gas that was inside both balloons

00:43:40 did not burn, and that gas is or was helium.

00:43:44 Now let's try these other balloons

00:43:46 and see if the same reaction takes place.

00:43:49 You ready?

00:43:50 Now be careful in terms of the observations that you make.

00:44:06 All right.

00:44:09 Was that the same kind of gas inside?

00:44:14 Now, there were so many different things that happened

00:44:17 in this combustion reaction compared to the other one.

00:44:21 What is one of the differences?

00:44:25 There was a lot of energy released in the form of,

00:44:31 well, in the form of sound, right?

00:44:33 Sound energy.

00:44:34 You heard the explosion.

00:44:35 There was also a big flame,

00:44:37 and for those of you who didn't see the flame,

00:44:39 what we're going to do now is repeat the experiment,

00:44:44 but turn off the lights.

00:44:45 So turn off the lights.

00:44:50 Are you ready?

00:44:53 Ah!

00:45:14 I told you that over there I didn't want

00:45:17 to find out if the thread burns.

00:45:20 I really didn't want to find out over here either.

00:45:23 Okay, let's go over to this one

00:45:29 and see what happens if we

00:45:32 be careful and put this like so.

00:45:35 Actually, I want to just try to point something out to you

00:45:39 because I told you at the beginning

00:45:42 it's very important to obey the safety regulations

00:45:45 when we do this experiment, right?

00:45:47 Now you have noticed as one of your observations

00:45:50 which you haven't told me about because I haven't asked you

00:45:52 as we move from this side of the table

00:45:55 to that side of the table

00:45:57 there are changes in the intensity of the combustion

00:46:00 and the associated reactions going along combustion, right?

00:46:03 Namely, the sound that is released.

00:46:06 And so what I'm going to try to do

00:46:09 and suggest that you do too

00:46:11 is cover up your ears

00:46:13 to protect your eardrums from

00:46:15 the possibility of puncture.

00:46:17 But I can't do that and do the experiment

00:46:19 so I have these earplugs.

00:46:21 Okay, so I'll put those on.

00:46:23 Now, if you can hear what I'm saying

00:46:46 you don't have your ears covered very well.

00:46:49 And I can tell from your reaction

00:46:52 you're laughing that you can hear what I'm saying.

00:46:54 So cover your ears very well.

00:47:08 Okay, alright.

00:47:10 I'll tell you what.

00:47:12 I'll tell you what, we'll do this experiment

00:47:15 one more time in the dark

00:47:17 and I'll be very careful.

00:47:18 So cover your ears.

00:47:42 Alright, now

00:47:44 what was inside the red balloon

00:47:47 was hydrogen gas.

00:47:49 Hydrogen gas is a very, very explosive gas

00:47:52 if it comes in contact with a spark or a flame.

00:47:55 What was inside the yellow balloons

00:47:58 was a mixture of hydrogen and oxygen gases

00:48:02 and that's a very, very dangerous mixture

00:48:04 and as you could see and hear

00:48:07 if you didn't have your

00:48:08 even if you had your ears covered very well

00:48:10 you could still hear the room vibrate.

00:48:12 I hope, Dr. Preston, this auditorium is still in good shape.

00:48:17 And the combustion reactions that we saw

00:48:21 demonstrate the explosive nature of hydrogen

00:48:25 and especially when mixed with oxygen.

00:48:29 Let's get this sodium acetate trihydrate out of the way

00:48:33 and carry out a different kind of a combustion reaction.

00:48:39 This combustion reaction we're going to carry out

00:48:42 inside this small plastic bottle

00:48:45 that has two nails driven into it

00:48:47 but the nails are not touching.

00:48:49 Why don't you show us a close-up of that.

00:48:51 You can't see the nails not touching

00:48:54 and into this I'm going to make a combustion chamber

00:48:58 out of this by taking a little bit of a fuel

00:49:01 in this case it's alcohol, ethyl alcohol

00:49:05 putting ethyl alcohol in there

00:49:09 and I'll do it with two of them

00:49:14 and then I'm going to stop the small plastic bottle like so

00:49:23 and I'll tell you that these two nails

00:49:26 are separated by about one to one and a half centimeter distance

00:49:30 and what I'm going to try to do next

00:49:33 is to see if the vapor of the alcohol

00:49:37 can be ignited as I put a spark

00:49:41 across the gap that we have between those two nails

00:49:45 and I'm going to put a spark using something

00:49:48 that we call a Tesla coil

00:49:57 I want to show you that

00:50:00 there's a spark coming across from this

00:50:04 this is a dangerous kind of an experiment

00:50:07 I don't know if you have had experience with it

00:50:10 but I want to show you that there's a spark coming from this coil

00:50:38 I'm going to put this spark across one set of nails

00:50:42 and see what happens

00:50:51 you didn't see it because you weren't paying any attention, right?

00:50:55 let's do one more in the dark

00:50:58 that's why we repeat experiments

00:51:01 let's do it in the dark

00:51:07 okay, I got it

00:51:12 and you see the alcohol vapor

00:51:15 when the spark jumps from one nail to the other

00:51:18 is ignited and burns and releases a great deal of energy

00:51:22 not too different from what happens

00:51:25 in the internal combustion engine that we use

00:51:28 except that the fuel there is a different kind of fuel

00:51:32 all right, let's do an experiment now

00:51:35 right over here

00:51:38 we have a very large beaker

00:51:41 this beaker has a volume of about 4 liters

00:51:45 and it has in it some water

00:51:48 actually, it's getting a little bit hot here

00:51:51 I'm going to take my coat off

00:51:54 is that okay to take my coat off?

00:51:57 actually, I'll take my tie off too, is that all right?

00:52:06 okay, how about if I take my shirt off?

00:52:13 I promise you, Frank, this is all decent

00:52:25 all right, I hope you agree with this

00:52:28 I can tell from your reaction that most of you agree

00:52:31 maybe all of you agree

00:52:34 this beaker has in it about 3.5 liters of water

00:52:37 and it's sitting on top of a magnetic stirrer

00:52:40 there's a spinning bar sitting at the bottom of the beaker

00:52:43 which you can't see very well

00:52:51 and I'm going to mix a couple of different chemicals

00:52:54 from these two bottles into this beaker

00:52:57 and see what happens

00:53:00 that's again why we do experiments

00:53:03 to see if anything happens

00:53:06 the first one I'll mix, I'll just put a little bit of this

00:53:09 nothing much happens

00:53:12 I add a little bit of this, something is beginning to happen

00:53:15 I add some of this

00:53:22 you know, what's a much better way of mixing chemicals carefully

00:53:25 is to use these medicine droppers

00:53:28 and that's what I'm going to try to do

00:53:34 you see anything developing down the middle?

00:53:37 what is it?

00:53:40 what does it look like?

00:53:43 it looks like a tornado

00:53:46 what color is it?

00:53:54 what color is the tornado itself?

00:53:57 green?

00:54:00 green

00:54:09 and if you know what you're doing

00:54:12 and you mix the right chemicals together

00:54:15 you can produce this effect right down the middle of the vortex

00:54:18 as it's called

00:54:21 that is created by the spinning bar in the liquid

00:54:24 see if I add the solutions to the side

00:54:28 you don't get the same effect

00:54:31 you've got to add the solutions of these chemicals

00:54:34 right to the center of the vortex

00:54:37 to get this tornado effect

00:54:40 and you notice that the color now is what?

00:54:43 orange

00:54:46 well enough about that

00:54:49 tornado

00:54:52 we can watch this for a long time

00:54:55 and the insoluble substance that's being formed

00:54:58 stays in the middle of the vortex

00:55:01 and if we add one or more of the reactants

00:55:04 then we can make that insoluble substance disappear

00:55:07 you know in science

00:55:10 especially in all sciences

00:55:13 we do experiments to find out what happens

00:55:16 and someone said

00:55:19 I don't know exactly who said this

00:55:22 when a phenomenon occurs

00:55:25 and everyone is capable of understanding what happened

00:55:28 we call that science

00:55:31 when a phenomenon occurs and very few people know what happened

00:55:34 we call that magic

00:55:37 the magician knows all the magic tricks that are involved

00:55:40 and this person went on to say

00:55:43 when a phenomenon occurs and no one understands what's happened

00:55:46 we call that a miracle

00:55:50 and I'll tell you that this is a mixture

00:55:53 of mercuric nitrate and potassium iodide

00:55:56 in the proper ratios to produce the insoluble

00:55:59 mercuric iodide which then eventually dissolves

00:56:02 to form a complex ion

00:56:05 which happens to be soluble

00:56:08 so enough about that experiment

00:56:11 was I turning off the wrong one?

00:56:14 was it on or off?

00:56:18 now I can see it now on my own monitor

00:56:21 thank you

00:56:24 okay what we're going to do is add a liquid

00:56:27 out of this bottle

00:56:35 see depending on the size of the bottle

00:56:38 and the shape of the neck of the bottle

00:56:41 and the opening you can add things sometimes very quickly

00:56:44 sometimes you can't add them as quickly

00:56:47 I will leave that one alone

00:56:50 we'll just add some out of here

00:56:59 and we'll add

00:57:06 some out of there

00:57:14 okay

00:57:28 and what's the old saying?

00:57:31 more is better, right?

00:57:34 so we'll go and add a little more

00:57:40 even a little more

00:57:45 wow

00:57:58 wow

00:58:01 use too much of it

00:58:04 okay

00:58:20 is anything happening?

00:58:35 applause

00:58:44 this is an example of what we refer to

00:58:53 got carried away with my t-shirt

00:58:56 you can still hear me all right?

00:58:59 okay this is an example of what we refer to

00:59:02 as a chemical oscillating reaction

00:59:05 the colors oscillate from one to another

00:59:08 and if you've been watching this now for a little bit

00:59:11 you've been making lots of observations about this

00:59:14 beyond the sequence of color change

00:59:17 I hope you've been making additional observations

00:59:20 for example what can you tell me about

00:59:23 first of all the sequence of the change?

00:59:26 what is it?

00:59:29 it goes white or colorless

00:59:32 and then a little bit of orange

00:59:35 and then it goes black

00:59:38 actually it's so deep blue it's black

00:59:41 but what has been happening to the time

00:59:44 that each color is lasting

00:59:47 is that the same or is it changing?

00:59:50 see the blue color

00:59:53 or the deep blue black color now

00:59:56 is lasting much longer than before

00:59:59 and this is one of the properties of this reaction

01:00:02 I want you to know

01:00:05 this is a very special reaction

01:00:08 it's so special and I won't tell you about it

01:00:11 it was discovered by two high school teachers

01:00:14 in 1973

01:00:18 and it was not until 1982

01:00:21 that a member of the National Academy of Sciences

01:00:24 published the explanation for this reaction

01:00:27 that's professor Richard Noyes from the University of Oregon

01:00:30 who published the explanation for this sequence of steps

01:00:33 involved in this reaction

01:00:36 the sequence of steps actually has in it about 24 steps

01:00:39 but two high school teachers discovered this reaction

01:00:42 in 1973 and published it

01:00:46 in the Journal of Chemical Education

01:00:49 which is an indication of how important it is

01:00:52 to make observations and try to make some sense out of the observations

01:00:55 and then come up with an explanation

01:00:58 so that the explanation can help you control

01:01:01 what happens to this chemical reaction

01:01:04 now let me move on very quickly

01:01:07 to a different kind of reaction system

01:01:10 and before I do that

01:01:14 I want to carry out one very special experiment

01:01:19 because it is the value of experimentation

01:01:22 that is what I'm trying to share with you tonight

01:01:25 before I do that

01:01:28 I want to read to you a short quotation

01:01:31 from Ira Remsen

01:01:34 who was a chemist at one time

01:01:37 and later on became the president of Johns Hopkins University

01:01:40 and this is what Ira Remsen had to say

01:01:43 this is when he was a little kid

01:01:46 and if you pay special attention to this

01:01:49 you'll see the point that I'm trying to get across tonight

01:01:52 it goes like this

01:01:55 while reading a textbook of chemistry

01:01:58 I came upon the statement

01:02:01 nitric acid acts upon copper

01:02:04 I was getting tired of reading such absurd stuff

01:02:08 copper was more or less familiar to me

01:02:11 for copper scents were then in use

01:02:14 I had seen a bottle marked nitric acid on a table

01:02:17 in a doctor's office

01:02:20 where I was then doing time

01:02:26 I did not know its peculiarities

01:02:29 but the spirit of adventure was upon me

01:02:32 having nitric acid and copper

01:02:35 I was ready to learn what the words act upon meant

01:02:38 the statement nitric acid acts upon copper

01:02:41 would be something more than mere words

01:02:44 all was still

01:02:47 in the interest of knowledge

01:02:50 I was even willing to sacrifice

01:02:53 one of the few copper scents then in my possession

01:02:56 I put one of them on the table

01:02:59 opened the bottle marked nitric acid

01:03:02 poured the liquid on the copper

01:03:05 and prepared to make an observation

01:03:08 but what was this wonderful thing which I beheld

01:03:11 the scent was already changed

01:03:14 and it was no small change either

01:03:17 a green-blue liquid foamed and fumed

01:03:20 over the scent and over the table

01:03:23 the air in the neighborhood of the performance

01:03:26 became colored dark red

01:03:29 this was disagreeable and suffocating

01:03:32 how should I stop this

01:03:35 I tried to get rid of the objectionable mess

01:03:38 by picking it up and throwing it out the window

01:03:41 I learned another fact

01:03:46 nitric acid not only acts upon copper

01:03:49 but it acts upon fingers

01:03:52 the pain led to another

01:03:55 unpremeditated experiment

01:03:58 I drew my fingers across my trousers

01:04:01 and another fact was discovered

01:04:04 nitric acid acts upon trousers

01:04:09 taking everything into consideration

01:04:12 that was the most impressive experiment

01:04:15 and relatively probably the most costly experiments

01:04:18 I have ever performed

01:04:21 it was a revelation to me

01:04:24 it resulted in a desire on my part

01:04:27 to see this remarkable kind of action

01:04:30 plainly the only way to learn about it

01:04:33 was to see its results

01:04:36 to experiment, to work in the laboratory

01:04:39 and that's what I'd like to show you now

01:04:42 this experiment

01:04:45 here's a copper penny

01:04:48 and what I'm going to try to do

01:04:51 is take this copper penny

01:04:54 you're beginning to see some change

01:04:57 I'll take this coat back

01:05:00 away from

01:05:03 you see some change

01:05:06 that's the nitric acid acting upon the copper

01:05:09 the liquid is green, yellow green

01:05:12 and there are fumes coming out

01:05:15 and because we want to obey the safety regulations

01:05:18 I'll take this stopper

01:05:21 oops, did I use the wrong size flask?

01:05:24 I did

01:05:27 that's not going to work too well

01:05:33 the copper penny is dissolving

01:05:36 and the brown gas that you see coming off

01:05:39 that is nitrogen dioxide

01:05:42 NO2, it's one of the pollutants

01:05:45 that we have in the atmosphere

01:05:48 and as long as I'm careful in shaking this

01:05:51 very slowly

01:05:54 I'll try not to have it escape

01:05:57 into the room

01:06:00 the next thing I want to try to do

01:06:03 is to try to stop the reaction

01:06:06 by taking the contents of this flask

01:06:09 and you can't see the color

01:06:12 it's so deep red

01:06:16 it looks deep brown, I mean it looks red

01:06:19 what I'm going to do is to try to pour this

01:06:29 like so

01:06:35 and here we have a solution

01:06:38 of copper nitrate

01:06:41 and this is water, I just poured it into water

01:06:44 and this flask is still full of the NO2

01:06:50 which we'll try to keep in there

01:06:53 until the end of the presentation

01:06:56 very quickly, another set

01:06:59 by the way, what has happened to the oscillating reaction now?

01:07:02 it just stopped

01:07:09 it's no longer oscillating

01:07:13 the chemicals that are being produced have been totally consumed

01:07:16 and the color that you see is the deep blue color

01:07:19 of the starch iodine complex

01:07:22 that has been produced

01:07:25 a couple of other quick experiments

01:07:28 before we go

01:07:31 these experiments cannot be done at home

01:07:34 because you don't have the chemicals

01:07:37 although this first one can be

01:07:43 what I have is some acetone

01:07:46 which I'm going to put into this dish

01:07:49 and I'm shifting discussion now

01:07:52 from talking about copper pennies

01:07:55 and nitric acids and indicators

01:07:58 and acid-base behavior

01:08:01 into a different set of chemicals altogether

01:08:04 I'm going to take this cup of polystyrene

01:08:07 and what I'm going to do is put this cup

01:08:10 into the acetone and see what happens

01:08:13 as I put it into the acetone

01:08:19 see the acetone dissolves

01:08:22 this man-made product

01:08:29 and that's what we do in chemistry

01:08:32 we can make some things disappear

01:08:35 but we can also make some things appear

01:08:38 I'm going to take a brown liquid

01:08:41 out of a different styrofoam cup

01:08:44 and mix it with an amber liquid

01:08:47 out of a different styrofoam cup

01:08:50 and we learned tonight

01:08:53 I hope that reactions don't take place

01:08:56 unless you mix them

01:08:59 sometimes they react right away

01:09:02 sometimes you just have to mix them real well

01:09:05 before a reaction takes place

01:09:13 now you see

01:09:16 in chemistry we can make things disappear

01:09:19 and we can make other things appear

01:09:36 laughter

01:09:39 applause

01:09:43 laughter

01:09:46 applause

01:10:04 this is an example

01:10:07 of a substance not too different from polystyrene

01:10:10 this is polyurethane foam

01:10:13 and this is how it's made

01:10:16 actually mixing those two reagents together

01:10:19 and this has a lot of different uses

01:10:22 it's mostly used for insulation purposes

01:10:25 in a variety of places

01:10:28 at home for example

01:10:31 or airplanes and so on

01:10:34 unfortunately one of the undesirable properties

01:10:37 is that it contains poisonous gases

01:10:40 which can cause harm

01:10:43 in fact can cause death

01:10:46 but I just want you to know

01:10:49 that it's a very simple substance

01:10:52 that is made in this fashion

01:10:55 now a couple of other experiments

01:10:58 that I want to show you

01:11:01 so that you can do them at home

01:11:04 laughter

01:11:24 well one of the experiments has to do

01:11:27 with using these two small pieces

01:11:30 of polarizers

01:11:33 and what you need to do

01:11:36 is to use a source of light

01:11:39 like a light bulb

01:11:42 or use a flash light

01:11:45 and to show everybody what's going to happen

01:11:48 I'm simply going to use the overhead projector

01:11:51 and instead of your small

01:11:54 two inches by two inches pieces

01:11:57 that you have in the packet that you'll get

01:12:00 what you should do when you get your small pieces

01:12:03 of polarizers you'll find that there's a small piece

01:12:06 of protective film on them

01:12:09 which you should peel off

01:12:12 and that's what I'm trying to do

01:12:15 peel this off

01:12:18 need somebody with long fingernails

01:12:21 okay I got one piece off right

01:12:24 and then the next thing you do

01:12:27 you do this with the two pieces of polarizers that you have

01:12:30 and then you get a piece of

01:12:33 baggies or ziplock

01:12:36 whatever brand you use

01:12:39 and you put one polarizer like this

01:12:42 on the source of light that you have

01:12:45 and I'm going to use actually the big ones

01:12:48 to have everybody see

01:12:51 and then notice what happens when the polarizers

01:12:54 are parallel to each other

01:12:57 the light comes through

01:13:00 when you rotate like so 90 degrees

01:13:03 the light will not come through

01:13:06 when you're at an angle of 45 degrees

01:13:09 some of the light comes through

01:13:12 the next thing that you do is you take this baggies

01:13:15 or you take any piece of film that you have

01:13:18 I'll take the piece of film that I just peeled off

01:13:21 like so

01:13:24 and I want to show you that you can see

01:13:27 at the 45 degree angle

01:13:30 here's another piece that somebody just gave me

01:13:33 we'll put that in there

01:13:36 and you can see

01:13:39 different light coming through

01:13:42 depending on the angle that you rotate

01:13:45 one of these polarizers to

01:13:48 this is a phenomenon called birefringence

01:13:51 but there's more that you can do with it

01:13:54 and since you were kind enough to help me with this

01:13:57 I want you to help me a little bit more

01:14:00 can you hold this polarizer up like so

01:14:03 and this requires two people

01:14:06 the next thing that you do is you try to stretch

01:14:10 if you stretch this

01:14:13 and you have the focus done right

01:14:16 you can then get these very interesting colors

01:14:19 thank you

01:14:22 you can get this color development

01:14:25 and if you take a piece of plastic

01:14:28 or a plastic cup like this

01:14:31 you can see the stresses and the strains in it

01:14:34 between those cross polarizers

01:14:37 so this is an experiment that you can do at home

01:14:40 using those two small pieces of polarizers

01:14:43 it's one of the properties of

01:14:54 one of the properties of the substances we call polymers

01:14:57 now one other experiment which I will describe to you

01:15:00 and then let you do it at home

01:15:03 inside each packet you will find a rubber band

01:15:06 and what you do with a rubber band is the following

01:15:09 you put the rubber band close to your forehead or close to your lip

01:15:12 and you feel it

01:15:15 and you try to describe what you feel

01:15:18 among other things you try to describe is the temperature of the rubber band

01:15:21 the next thing that you do

01:15:24 and I'll move sideways so you can see what I'm doing

01:15:27 move the rubber band forward and quickly stretch it

01:15:30 and put it back on your forehead or on your lip

01:15:33 and say or report what the temperature change is

01:15:36 the next thing you do after that

01:15:39 with the rubber band stretched release it

01:15:42 and put it on your forehead and again report what the temperature is

01:15:45 you will observe a change in temperature

01:15:48 as the rubber band is stretched

01:15:51 and as the rubber band is released

01:15:54 and this stretching and releasing of the rubber band

01:15:57 is related to the properties that the rubber band has

01:16:01 and all these instructions will be in what I mail you out

01:16:04 once you send me the set of instructions

01:16:07 once you send me the gummed label for the set of instructions

01:16:10 now the other experiment I want to try to do

01:16:13 which is not in your handout

01:16:16 is to take still another balloon

01:16:25 blow up this balloon like so

01:16:28 release the air just a little bit

01:16:31 and then tie the balloon

01:16:34 to demonstrate still another property

01:16:37 of this rubber

01:16:40 what I will do is take a very sharp needle

01:16:43 and I want you to come as close as you can

01:16:46 this is a very sharp needle

01:16:49 you have to be very careful in handling this needle

01:16:52 and what you do is

01:16:55 you take still another chemical

01:16:58 or a mixture of chemicals, in this case some Vaseline

01:17:01 and you lubricate this very very carefully

01:17:04 moving in the right direction

01:17:07 not to hurt yourself

01:17:10 and then the next thing you try to do is

01:17:13 to put this needle through the balloon

01:17:16 without having the balloon puncture

01:17:19 so let's see if we can do that

01:17:23 those of you who weren't here last year

01:17:26 can see the balloon is still there

01:17:34 and there is actually a hole on both sides of the balloon

01:17:37 I want you to listen very carefully

01:17:40 just listen, just listen

01:17:43 see if you can hear the air coming out

01:17:47 hear the air coming out?

01:17:50 there are two big holes here

01:17:53 in fact the balloon is getting smaller

01:17:56 and there is nothing really magical about this

01:17:59 because if I puncture the balloon

01:18:02 it punctures right away

01:18:05 now let's do this experiment one more time

01:18:08 so that you can see exactly how I am doing this experiment

01:18:11 and how the magicians do it

01:18:14 so let's get on

01:18:25 you blow up the balloon

01:18:28 you let some air out

01:18:31 you tie the balloon

01:18:34 and then if you look very carefully at this balloon

01:18:37 and you come up as close as you can

01:18:40 with the camera

01:18:44 do you see this spot right here?

01:18:47 does everybody see this spot?

01:18:50 this spot is thicker than the rest of the balloon

01:18:53 there is another spot right near the place where you blow up the balloon

01:18:56 where it's also thicker

01:18:59 now if you put this needle

01:19:02 which has been lubricated to just make life a bit easier

01:19:05 if you lubricate this needle

01:19:08 and you put it right through that thick part

01:19:12 so come in closer

01:19:15 can you see the thick part?

01:19:18 you just stay put I'll find it

01:19:21 I'll find you

01:19:24 what we'll do is go through this

01:19:27 you see it?

01:19:30 and we come out the other end

01:19:33 and you see the balloon does not puncture

01:19:36 that has to do with the stretched rubber

01:19:40 where we can drive this very sharp needle through the balloon

01:19:43 and of course when we get done

01:19:46 we can pop the balloon like that

01:19:49 well these are some of the experiments that I wanted to share with you tonight

01:19:52 I know the hour is late

01:19:55 and I know there are many other experiments that we could have done

01:19:58 and I'll try to do some of these again next year

01:20:01 you've been a very good audience

01:20:04 I want to thank you for coming

01:20:07 and don't forget as you leave the room

01:20:10 get a packet from Santa or one of Santa's helpers

01:20:13 and send me that information

01:20:38 and I want you to acknowledge his help

01:20:41 that's Fred Juergens

01:20:44 Fred is over here

01:20:47 and the other person is a graduate student

01:20:50 in chemistry at Georgetown University

01:20:53 who also spent several days getting all of these things ready

01:20:56 and that's Ken

01:20:59 Ken will you take a bow?

01:21:07 thank you and good night