00:00:01 Academy of Sciences and the National Research Council. On behalf of Frank

00:00:05 Press, the president of those of the Academy, I'd like to welcome you here

00:00:10 this evening for what will be a very interesting and entertaining and

00:00:15 scientific evening. We are trying to establish a tradition here of having a

00:00:23 holiday science lecture of this type every year. This is not the first

00:00:29 Academy to try to do this sort of thing. The tradition actually began with the

00:00:34 Royal Society in the 1840s in Great Britain, some 20 years before the

00:00:41 National Academy of Sciences of the United States was chartered by the

00:00:46 Congress in 1863. Tonight we have Bassam Shokashiri, the assistant director of the

00:00:53 National Science Foundation for Science and Engineering Education, as our guest

00:00:58 lecturer. Bassam has had a very distinguished career both as a scientist

00:01:03 and a science educator. He spent the decade of the 1970s and the early 80s at

00:01:11 the University of Wisconsin-Madison before joining the National Science

00:01:15 Foundation staff in 1984. He's the author of textbooks, teaching guides, teaching

00:01:25 aids, demonstrational materials in chemistry, has worked actively with a

00:01:31 number of science museums in developing interactive chemistry educational

00:01:38 exhibits, most recently the Museum of Science and Industry in Chicago. It gives

00:01:45 me a great deal of pleasure to present Bassam Shokashiri, who will be our guest

00:01:51 lecturer tonight, and take us to his laboratory.

00:02:06 Thank you very much and it's a delight to be back at the Academy this evening.

00:02:10 This is the third year in a row that we do this and I'm delighted to see so many

00:02:15 people who came before and I don't recognize everyone so there must be new

00:02:20 people who are with us this evening. It is indeed the holiday season and we

00:02:25 ought to be enjoying the season and be as jolly as possible and that's why we

00:02:31 have a number of very colorful scientific experiments that we will go

00:02:37 through this evening and the whole idea is for you to be convinced that science

00:02:43 is indeed fun. So I want you to sit back and relax and watch what's going to

00:02:47 happen and try to think about what you see, try to reason out what you observe,

00:02:55 try to make some sense out of these observations, and then we'll all have

00:02:59 some fun together. Before we get on with this I want to thank the Academy for

00:03:06 hosting this activity once again and I'm glad it is the beginning of a tradition.

00:03:10 I also want to thank a number of people who have spent long hours getting all of

00:03:16 these different items ready because I was busy doing some other things at the

00:03:21 National Science Foundation and I especially want to acknowledge John

00:03:25 Hudson and Fred Juergens and Tim Watt and Judy Worthley. It's very important to

00:03:33 recognize their contributions and I tell you right off the bat anything that

00:03:38 works tonight is because they did it and whatever doesn't work because I'm not

00:03:41 doing it right. So in doing experiments we always have to be very careful about

00:03:47 obeying safety regulations and you'll see that for the rest of the evening I'll

00:03:52 put my goggles on to protect my eyes from any splashes that might develop as

00:03:56 we do some experiments and you also will notice that we have two

00:04:02 fire extinguishers that we have available in case an accident develops.

00:04:09 We're not planning on anything going out of control and we will proceed with the

00:04:16 idea that we want to be as cautious and as safe as possible in doing experiments.

00:04:21 Well the first set of experiments that we will do will do them over here

00:04:28 involving something that you have access to namely soap bubbles. It's a lot

00:04:36 of fun to play with soap bubbles. Everybody at one time or another has

00:04:38 done this.

00:04:47 And you see the soap bubble full of air just floats down. I'm sure all of you

00:04:53 have noticed the pretty colors that the soap bubbles have and one thing I'm

00:05:01 going to try to do is take this soap bubble and see if I can, oops, try it

00:05:06 again.

00:05:15 That got away from me. But if you fan the soap bubble above it can prevent it

00:05:25 from going down. See that right? That doesn't make too much sense does it?

00:05:36 If you fan it under the soap bubble it falls down. There must be something to

00:05:41 this. Let's do it one more time.

00:05:50 And what you ought to do is think about why it is that the soap bubble floats

00:05:54 upward when we fan it right above the position of the soap bubble. It is

00:06:01 related to a very well-known scientific principle and it is the principle

00:06:08 actually is Bernoulli's principle and it's a principle that everybody has

00:06:13 observed at one time or another. Every time that you take a shower, if

00:06:17 you have a shower curtain, when you turn the shower on you see that the shower

00:06:20 curtain moves in which direction? Moves in towards the place where the water is

00:06:25 flowing. That is because of the removal of air from that region because the

00:06:33 water is rushing very fast and that's what we're doing here. When we're fanning

00:06:36 this we're reducing the pressure above the soap bubble so the soap bubble gets

00:06:40 to float. Well we're going to do a couple of other experiments now involving soap

00:06:45 bubbles and to do that I'm going to call on Fred Juergens to come and help out

00:06:49 because it takes two people to do those experiments. Fred came all the way from

00:06:53 Madison, Wisconsin to help us tonight and the experiment that we're going to do

00:06:59 has to has to has to do with something we call combustion. Combustion is simply

00:07:06 the burning of an object in air and what we're going to do is create some soap

00:07:13 bubbles that are filled not with air but are filled with hydrogen gas and then

00:07:20 we're going to see what happens to those soap bubbles as we subject them to

00:07:25 a flame. So

00:07:38 now Fred is blowing some hydrogen gas into the soap and you see the bubble

00:07:44 goes up, doesn't stay up very much, let's see if we can, I don't have to fan that

00:07:56 bubble, you see it goes up all the way because hydrogen, what's the observation?

00:08:01 Hydrogen is what? Heavier or lighter than air? It's lighter than air, okay. Now what

00:08:07 we'll do is I'll start

00:08:15 here's an example of controlled combustion and we need to have, I'll step

00:08:20 away this way, we need to have a couple of soap bubbles going up, let's see what

00:08:24 happens to them.

00:08:28 You see the bubbles burn when I, there you go, now very slowly, whoops that's the

00:08:34 point of stay, Fred is going to introduce, introduce into this mixture some oxygen

00:08:43 gas so we're going to mix hydrogen and oxygen together, let's see what happens.

00:09:14 There we go.

00:09:23 That was minor repair here, okay. All right as he's repairing this special pipe that we

00:09:29 use to blow the soap bubbles with, let's take a look at these balloons that we

00:09:33 have up here and those balloons are held with a string and that tells us that the

00:09:40 gas that's inside the balloon is what? Heavier or lighter than air? Lighter than

00:09:45 air and let's find out what's in this balloon, you think it's helium? Who said

00:09:52 helium? How do you know it's helium? Because of what? Don't be shy, speak out.

00:10:03 You think it's helium because you've seen helium balloons before and you know

00:10:07 from what you've learned before that helium is a gas lighter than air. Let me

00:10:12 tell you that helium is a gas which does not burn like the hydrogen was burning.

00:10:18 Are we ready to go with this again? Okay let's try this one.

00:10:23 Now you see what happens.

00:10:28 Okay, one more.

00:10:46 Okay.

00:10:49 Let's look, let's look at, let's look at these balloons over here. Thank you, Fred.

00:11:00 These balloons have gas in them and the gas obviously is lighter than air. Let's

00:11:07 find out if they're filled with helium. If it's helium, then the gas will not

00:11:11 burn, right? If it is not helium, well, we'll find out. Here we go.

00:11:19 Did you see a flame there? Okay, now that flame is caused by the combustion of

00:11:29 hydrogen gas, which is burning with air, with oxygen that's in the air. Now let's

00:11:34 do this experiment in the dark and see what happens to...

00:11:41 Okay, ready? You can see the...

00:11:54 Now let's move back to those balloons that we were working with before, and we want

00:12:03 to find out if they have anything in them that burns, that undergoes

00:12:06 combustion. So here we go.

00:12:10 Now, what should I do next? Skip this and go to another one, or should I try this balloon? Try this one?

00:12:29 Should we try it in the dark? In the dark, okay.

00:12:35 I want you to cover your ears.

00:12:40 Okay, so we've seen some examples of combustion reactions. Some are controlled

00:13:06 combustion reactions, and some went out of control. They exploded. That's what an

00:13:09 explosion is. It's a reaction that goes out of control. It goes so fast that it

00:13:17 is out of control. Now what we'll do is just shift gears, as we will do

00:13:21 throughout the evening, and look at these set of cylinders where we have

00:13:26 some colored liquid in each of these cylinders. And what I'm going to do is

00:13:32 take a very cold substance, which we call dry ice. Dry ice is a substance that

00:13:40 has a temperature of minus 78 degrees Celsius, and here's a chunk of dry ice.

00:13:47 I'll just throw it up here, and you can watch the monitor. You can see it. It's

00:13:53 very cold. That's why I'm wearing the gloves, to protect my hands from frostbite.

00:13:57 Dry ice is solid carbon dioxide. It's a gas, and what we're going to do is drop

00:14:05 chunks of dry ice into the cylinders that you see in front of you. So here we

00:14:11 go. Just take some dry ice.

00:14:20 Am I dropping a dry ice into every cylinder? Every other one. So that's a

00:14:26 pattern that I'm following, and that's what we look for in science. We look for

00:14:31 patterns as we make observations about different chemical systems or different

00:14:35 scientific systems, and we see lots of interesting things happen. You see

00:14:40 bubbles forming. These are carbon dioxide bubbles. You can also see in some of the

00:14:44 cylinders that the color is beginning to change. These cylinders are arranged in

00:14:48 pairs so that you can compare any changes that take place in any pair as we

00:14:54 go along. For example, you can see here that the color has changed to what?

00:14:59 Almost colorless, right? And has there been a change here in color? How about here?

00:15:05 A little bit here, right? How about here? And about here? Now what? There is some,

00:15:12 what's this stuff that's coming off the top here? Fumes, right? Fumes, somebody said,

00:15:17 steam. What do you think it is? You think it's carbon dioxide? Well, carbon dioxide

00:15:24 is an invisible gas. You can't see it. What you see here is, what is it, oxygen?

00:15:33 No, that's an invisible gas too. Steam, somebody said steam. Steam is an

00:15:40 invisible gas too. We don't see it. Somebody said condensation. What you see

00:15:46 is condensed water vapor. It looks like fog, right, or cloud. That's what it is.

00:15:52 It's condensed water vapor, and this is what happens when you have a colorful

00:15:58 set of reactions taking place in a holiday season when everything is, you

00:16:03 know, so jolly and everybody is in a very special and happy mood. It's important.

00:16:10 Uh-oh.

00:16:25 Hello, Merry Christmas. So glad to see you, Santa. I heard you were celebrating

00:16:32 Christmas, so I thought I'd drop by early. Well, I'm glad you did. It's nice to be

00:16:36 here. Do you have some... I have a few things here for you. You have a few things for me? Uh-oh. I've been good, I can tell you that.

00:16:42 Well, the lump of coal isn't for you. Oh, okay. You don't have to worry about that.

00:16:46 Let's see, what do I have here?

00:16:52 Can't trust these elves.

00:16:56 There we are. I have a Christmas card for you.

00:16:58 It says, there was a young man in D.C. who said, Christmas time, ah, that's for me.

00:17:05 I'll show you some magic. Forget what is tragic, or my name's not Shaka Sheree.

00:17:10 That's good.

00:17:17 And, next thing I have for you, right down your alley. Oh, thank you, thank you. Can I play with them now?

00:17:25 Well, please do. Alright, alright, let's see what it says here.

00:17:33 It says, follow instructions, okay. So, I have to read the instructions carefully.

00:17:40 Okay, open the wrapper. Did that right? Did that right, okay. Bend carefully, and see what happens, okay.

00:17:50 Should I bend it? Yeah, that's very nice. Put that up there. Try the other one too.

00:18:00 Would you like me to try those in the dark?

00:18:05 Okay, that's a nice Christmas color. How about this one?

00:18:20 Here's one more.

00:18:28 Well, thank you very much, Santa. That's very, very kind of you to bring these.

00:18:32 Are these combustion reactions, or what kind of reactions are those?

00:18:36 Oh, not at all. Those are redox reactions.

00:18:38 Redox, oh, I see, I see. We'll have to talk about that later, Santa.

00:18:43 Just a few things at the North Pole, you know.

00:18:45 Right, right.

00:18:46 And, I have one other thing for you.

00:18:47 Yes?

00:18:48 There you are.

00:18:49 Oh, my goodness.

00:18:50 Just for your directorate.

00:18:51 National Science Foundation, Directorate for Science and Engineering Education, Mathematics, Science and Engineering.

00:18:58 Can I look in there?

00:18:59 Please do.

00:19:00 Oh, my goodness. Oh, there are lots of goodies in here.

00:19:04 Another light stick.

00:19:05 Uh-huh.

00:19:06 My goodness.

00:19:10 And, a button that says, Science is Fun.

00:19:13 True, true.

00:19:14 And, some instructions on blue paper and green paper and pink paper.

00:19:22 Curious.

00:19:23 And, a few other things now. Is this just for me?

00:19:27 Well, because this is such a tight group, I've got one for everybody here. What do you think about that?

00:19:32 Oh, that's great. That's great. That really is great.

00:19:35 There are a few other goodies in here.

00:19:37 I guess we'll let everybody look at what you've brought for them.

00:19:42 But, let's see.

00:19:43 Here's a rubber band.

00:19:44 Now, what's that for?

00:19:45 I'm supposed to do something.

00:19:46 No, no, no.

00:19:47 Not for that.

00:19:48 Maybe the instructions tell us about that.

00:19:50 Let's see.

00:19:51 Instructions tell us about that.

00:19:53 Oh, yeah.

00:19:54 Investigating rubber bands.

00:19:55 A whole set of instructions.

00:19:57 Well, that's very, very kind of you.

00:20:00 Oh, yeah.

00:20:01 Investigating rubber bands.

00:20:02 A whole set of instructions.

00:20:03 Well, that's very, very kind of you, Santa.

00:20:06 I'm sure everybody will appreciate working with these experiments.

00:20:10 And, I want to, before you go, I just want to ask you if you, can you stay or are you in a rush?

00:20:18 I have a lot of work to do.

00:20:19 I know you do.

00:20:20 I know you do.

00:20:21 We have a very special salute for you.

00:20:23 And, I'd like to ask Fred to come out and help us with this salute in keeping with the

00:20:28 holiday season and what's coming up here.

00:20:31 So, Fred, this is just for you, Santa.

00:20:36 I hope you have a good year.

00:20:46 Merry Christmas.

00:20:47 We wish you a Merry Christmas and a Happy New Year.

00:20:52 Very nice.

00:20:53 Very nice.

00:20:54 That's a great song.

00:20:59 Very nice.

00:21:00 Thank you.

00:21:01 Thank you.

00:21:02 Well, I do have to get going.

00:21:05 I do have to get back to the pole.

00:21:07 My very favorite song.

00:21:08 So, let's everybody sing it.

00:21:10 We wish you a Merry Christmas.

00:21:12 We wish you a Merry Christmas.

00:21:15 We wish you a Merry Christmas and a Happy New Year.

00:21:22 Well, as I was saying before I was pleasantly interrupted, we want to do some experiments

00:21:37 with dry ice.

00:21:38 And you see what has happened now with these different colorful reactions.

00:21:43 These are actually reactions between substances we call acids and bases.

00:21:49 And we have a different set of substance in each one of these cylinders, actually in each

00:21:55 pair of cylinders that we call indicators.

00:21:58 They indicate to us that a reaction has taken place.

00:22:01 Let's just put some more dry ice in here because it looks so nice bubbling, right?

00:22:06 Doesn't it?

00:22:12 And we think about the condensed water vapor that you see, right?

00:22:17 Just watch what happens to this as I blow on it.

00:22:20 What happens to it?

00:22:21 The condensed water vapor, does it go up or go down?

00:22:24 It goes down.

00:22:25 That's because the condensation is taking place on carbon dioxide and carbon dioxide

00:22:30 gas is heavier than air so it goes downward.

00:22:34 I'm going to take some of these chunks of dry ice and put them in this plastic trough

00:22:40 that has in it some water, actually some hot water, and you see what happens.

00:22:46 What does that look like now?

00:23:03 It looks like fog again, alright?

00:23:05 That's the condensation taking place on the carbon dioxide that's bubbling away.

00:23:12 Okay, let's move on and do a few other experiments.

00:23:17 Boy, I'd just like to see what else he's got in here.

00:23:20 Lots of other things in there.

00:23:22 We'll just look at that a little bit later and move on and try to do experiments back

00:23:31 in the combustion area except that this time we're going to do these experiments in these

00:23:37 small plastic bottles that have in them two nails.

00:23:42 We stuck two nails in them that are separated by about half a centimeter and we have a cork

00:23:47 on top and we have a little bit of a liquid at the bottom.

00:23:53 And we have a couple of these bottles and what we will do is take a device called a

00:24:01 Tesla coil that produces a spark.

00:24:04 I'm going to show you the spark.

00:24:07 Here's a rod of metal that I'm holding in my hand very tightly and you can see the spark.

00:24:14 Now, can you turn the lights down a little bit?

00:24:17 See the spark?

00:24:20 Okay, now we turn the lights up again and pay close attention and we'll see what happens

00:24:26 when we put this source of a spark to the side of one of the bottles that touches the

00:24:33 nails or across the nails.

00:24:36 You see that?

00:24:39 You heard that, right?

00:24:42 Maybe if we do the next one in the dark.

00:24:45 Let's do the next one in the dark.

00:24:49 Are you ready?

00:24:52 In the dark, in the dark.

00:24:55 Are you ready?

00:24:58 In the dark, in the dark.

00:25:01 Are you ready?

00:25:03 In the dark, in the dark.

00:25:06 In the dark, in the dark.

00:25:23 Now these were examples of combustion of ethyl alcohol caused by a spark jumping

00:25:32 between the two nails that are separated by about half a centimeter.

00:25:35 It's a combustion reaction of the alcohol vapor, not terribly different from the combustion

00:25:41 reaction that takes place in a car engine except that the fuel there is not alcohol

00:25:46 but is gasoline, which is a mixture of hydrocarbons.

00:25:50 And because of the relief of energy that we saw in the form of light, in the form of heat,

00:25:58 and also we saw that work can be done because of that combustion reaction.

00:26:03 The corks in every case jump.

00:26:06 I don't know where they are.

00:26:07 Did anybody catch them?

00:26:08 They're gone.

00:26:09 You did.

00:26:10 You got one.

00:26:11 Okay?

00:26:12 So this is an example then of another example of combustion reaction.

00:26:18 Let's take this drop out of the way and do a couple of other experiments.

00:26:23 We're going to do these experiments rather quickly, and these are the kinds of experiments

00:26:32 that some of you might be able to do at home.

00:26:35 What I would suggest you do is when you get your Christmas presents from Santa Claus,

00:26:40 if you leave at the end of the presentation tonight, if you look at the instructions and

00:26:44 see if you can do some of these experiments at home.

00:26:47 The principle is the same, except that the devices that I will use now are not available

00:26:54 to you at home.

00:26:55 But the principle is the same in terms of testing whether household chemicals are acidic

00:27:01 or basic.

00:27:03 And I have a device here called the pH meter, which I will use to measure the pH of a variety

00:27:09 of substances.

00:27:11 This is an electrochemical device that tells us what the pH value of the substance is.

00:27:17 We define the pH scale in such a way that a substance that has a pH value of 7 is said

00:27:24 to be neutral.

00:27:25 If a substance has a pH value higher than 7, then it's said to be basic or alkaline.

00:27:31 If a substance has a pH value lower than 7, then it is acidic.

00:27:38 And so the pH scale is a useful scale that helps us tell what the pH, what the acidity

00:27:44 or the basicity of a variety of substances are.

00:27:48 And then what I will ask you to do is to look at this device, which is a readout device

00:27:55 connected to the electrochemical probe that I have here.

00:28:02 And I will simply place different liquids.

00:28:07 Here's some Coke.

00:28:09 Do you think Coke is acidic, basic, or neutral?

00:28:14 Acidic, basic, does anyone think it's neutral?

00:28:18 Neutral?

00:28:19 Well, how do we get to find out?

00:28:21 We find out by doing an experiment, right?

00:28:24 By measuring, by using this probe to measure whether it's acidic or basic.

00:28:29 And remember now, a pH value of 7 means it's neutral.

00:28:33 Lower than 7, it's acidic.

00:28:35 Higher than 7, it's basic.

00:28:37 So we put this in there, we turn this on, and the pH value is quite low, right?

00:28:46 It's about 2.3.

00:28:48 It fluctuates a little bit, can you see that?

00:28:51 So Coke is quite acidic compared to ordinary water.

00:28:59 Pure water is neutral, it has a pH of 7.

00:29:04 Tap water may have a pH value different than 7 depending on what else is dissolved in it.

00:29:10 So let's move on and test a couple of other things.

00:29:15 Between measurements, we have to rinse this electrode.

00:29:21 And let's see, what other household items do I have around here?

00:29:25 I have lots of things.

00:29:34 I have some vinegar.

00:29:36 Do you think vinegar is acidic or basic?

00:29:40 Acidic?

00:29:41 Well, let's find out.

00:29:42 A little bit of vinegar.

00:29:52 And vinegar is acidic.

00:30:03 How about ammonia, do you think ammonia is acidic or basic?

00:30:06 Acidic.

00:30:12 Well, we've got all three choices called off now, right?

00:30:16 So we'll find out.

00:30:20 Take a little bit of...

00:30:37 Well, basic, right?

00:30:41 Ammonia is basic.

00:30:42 Well, let's see, what else do we have here?

00:30:45 Windex, do you think that's acidic or basic?

00:30:48 Basic.

00:31:00 Pretty colors all over the place, right?

00:31:03 Let's see.

00:31:04 In between, we take the electrode and we rinse it.

00:31:11 Put it in.

00:31:15 Acidic, basic, or neutral?

00:31:21 It's very basic, right?

00:31:23 Okay, let's see, what else do we have here?

00:31:33 Spanish, do you think that's acidic or basic?

00:31:41 Acidic.

00:32:05 Spanish is very acidic.

00:32:08 Now, all of these items that I've worked with are common household items

00:32:13 that you should be able to test whether they're acidic or basic

00:32:17 as you do the experiment and they're suggested in what Santa Claus has brought.

00:32:22 You have to be very careful in doing these experiments

00:32:25 and not to drink any of the items except the ones that we know are safe to drink,

00:32:31 like the Coke, for example.

00:32:34 Antiseptic.

00:32:38 Maybe some of you don't think it is safe.

00:32:41 Look, I have another can here of Diet Coke.

00:32:44 Do you think that's acidic or basic?

00:33:04 Okay.

00:33:20 You might want to compare the Diet Coke with the regular Coke

00:33:28 to see whether they are about the same pH value or not.

00:33:32 That's one of the experiments that you might do at home.

00:33:36 So we'll turn this off now and ask you to think about these different experiments

00:33:45 as you make observations about the various chemicals that you come in contact with.

00:33:52 One other experiment, by the way, that I want to suggest that you do at home,

00:33:57 everybody has seen eggs, right?

00:34:01 I've got two eggs right here.

00:34:07 I'll tell you that one of these eggs is a hard-boiled egg and the other one is not.

00:34:12 And without cracking them, do you think we can tell the difference between them?

00:34:16 Yeah? How?

00:34:18 Spin them, okay?

00:34:20 Let's see, I spin this one.

00:34:22 There's one.

00:34:24 I'll put it on the side.

00:34:26 I'll spin the other one.

00:34:28 Is this the hard-boiled one?

00:34:34 How about this one?

00:34:36 Let's try to spin it as hard as I can.

00:34:40 Now how can we prove that this one is the hard-boiled one and this one is not?

00:34:44 Crack them, right? We'll crack them.

00:34:46 But before that, before I do that, I want you to think about the reason why

00:34:50 you can tell which one is the hard-boiled egg and which one is the soft-boiled egg.

00:34:55 Let's see if we can bring about a change here.

00:35:00 I need some place where I can crack these.

00:35:02 Do I have to crack both of them or just one of them?

00:35:06 Which one?

00:35:08 They're all.

00:35:10 I thought you were going to say they're all one.

00:35:12 There you go, okay?

00:35:22 Here's the hard-boiled one.

00:35:24 That's the one that spins faster.

00:35:26 I want you each to think about why that's so.

00:35:28 Just to do this again.

00:35:30 Here's another egg.

00:35:32 This is their all one, right?

00:35:34 And just to prove to you that there's nothing magical about this egg,

00:35:38 here it is.

00:35:42 It's a hard-boiled egg.

00:35:48 Okay?

00:35:50 So you think about why, no, you never eat or put anything in your mouth,

00:35:56 eat or drink when you're doing experiments.

00:35:58 You never eat or put anything in your mouth, eat or drink when you're doing experiments

00:36:04 because you have to be very careful about not getting any unsafe chemicals into your body.

00:36:11 And I've touched a variety of different chemicals tonight,

00:36:14 that's why I'm not going to eat those without washing my hands first

00:36:19 and making sure that this is a clean vessel.

00:36:22 Okay, so we've talked about now household items.

00:36:28 Let's ask you to look at this part of the table here

00:36:34 where we have not only the musical speakers that I'm going to take out of the way,

00:36:38 but we have three flasks.

00:36:44 And two of them are sitting on a cork ring.

00:36:51 And what I'm going to do is take some coins,

00:36:54 take a couple of coins,

00:36:56 open this stopper,

00:36:58 and drop the coins in,

00:37:05 put this again,

00:37:07 stopper this again,

00:37:09 and we'll see if anything happens as the reaction goes along.

00:37:14 You see anything happening yet?

00:37:16 Watch the monitor.

00:37:18 What's turning color?

00:37:26 You see any color change here?

00:37:30 Right?

00:37:32 What else do you see happening over here?

00:37:35 Bubbles.

00:37:36 What else is happening over here?

00:37:39 What's getting lower?

00:37:41 The liquid.

00:37:42 You don't know it's water, do you?

00:37:44 The level of the liquid it's getting.

00:37:46 What's happening over here?

00:37:49 The liquid is getting pink

00:37:51 The liquid is getting pink

00:37:53 and the level of the liquid is...

00:37:56 All kinds of interesting things are happening, right?

00:37:59 So we can watch and see

00:38:01 how this develops.

00:38:04 It may take a little longer for more things to happen.

00:38:08 We'll keep an eye on it.

00:38:09 We're not in a rush, right?

00:38:10 We've got more time.

00:38:11 And as we do that,

00:38:13 I want you then to come back for a second

00:38:16 and look at these three light sticks

00:38:19 that Santa Claus brought to me.

00:38:21 These are examples,

00:38:23 not of combustion reactions,

00:38:26 or...

00:38:27 What did he say they were?

00:38:29 Redox reactions?

00:38:30 Well, I guess they are a form of a redox reaction.

00:38:33 They are actually a form of a chemical reaction

00:38:36 that we call chemiluminescence.

00:38:40 I know that's a long word,

00:38:41 it's a complicated word,

00:38:42 but it's really not all that mysterious.

00:38:45 Chemiluminescence is a phenomenon

00:38:48 that refers to the release of energy

00:38:52 not in the form of heat,

00:38:54 as we had in a combustion reaction,

00:38:56 but in the form of light.

00:38:58 And all three of these light sticks

00:39:00 are at room temperature.

00:39:02 Neither one of them has gotten warm.

00:39:05 And let me just be sure that Santa Claus

00:39:08 and his elves did this thing right.

00:39:10 They were supposed to put a light stick in each...

00:39:13 Yeah, they did.

00:39:14 They put a light stick in there

00:39:15 and a set of instructions,

00:39:17 and a set of instructions.

00:39:19 So you get to do an experiment at home

00:39:22 with this phenomenon of chemiluminescence.

00:39:25 And just to show you this phenomenon again in the dark,

00:39:28 let's turn down the lights.

00:39:31 And you can see that this is a pretty

00:39:36 efficient light system.

00:39:37 I can use it to see my way around.

00:39:40 I can also choose one of the three

00:39:45 beautiful colors that are produced

00:39:47 because there are different chemicals

00:39:50 involved in these reactions.

00:39:51 Now with the lights on,

00:39:52 what I'd like to ask you to do

00:39:55 is to watch very carefully

00:39:57 as I take two liquids

00:40:00 out of these plastic bottles.

00:40:03 This plastic bottle in my left hand

00:40:05 has a colorless clear liquid in it.

00:40:08 The plastic bottle in my right hand

00:40:10 has a colored and clear liquid,

00:40:15 a blue liquid.

00:40:16 And what I'm going to do

00:40:18 is mix those liquids

00:40:20 in this funnel that I have over here.

00:40:23 I'm going to try to do this in the dark

00:40:25 and we'll see what happens.

00:40:26 Okay.

00:40:33 This is another example of chemiluminescence

00:40:37 where energy is released

00:40:40 in the form of light,

00:40:42 not in the form of heat.

00:40:45 And just to show you that...

00:40:47 Put the lights up, please.

00:40:49 You cannot see the chemiluminescence here

00:40:52 except if it's dark.

00:40:53 So put the lights down, Dave, please,

00:40:55 a little bit.

00:40:56 Can you see it's fading?

00:40:57 Let's do it one more time.

00:41:04 Are the lights on?

00:41:07 Are the lights off?

00:41:11 It's a lot prettier with the lights off, right?

00:41:14 Okay.

00:41:15 This...

00:41:25 This is part...

00:41:26 Put the lights on, please.

00:41:27 This is part of what people refer to

00:41:30 as the magic of chemistry.

00:41:32 Actually, there isn't anything magical about it

00:41:34 if you understand what's going on.

00:41:36 And that's why we study science,

00:41:38 chemistry being one of the fundamental sciences.

00:41:40 We study science in order to try to understand

00:41:42 what's going on and to control

00:41:44 these various chemical systems

00:41:46 to help us produce products

00:41:50 that we can benefit from

00:41:51 and to help us live in an environment

00:41:54 that is clean

00:41:56 and an environment that is healthy.

00:41:59 Now I want to ask you

00:42:01 to focus your attention

00:42:04 on this part of the lecture table over here.

00:42:09 I'll take the light sticks away.

00:42:12 Before we focus our attention over here,

00:42:15 can we go back and look at the receiving vessel

00:42:18 that we use in this chemiluminescence reaction

00:42:21 and see what color this is?

00:42:23 What color is it now?

00:42:25 Dark black, yeah.

00:42:27 Dark black.

00:42:28 And you see there is a difference

00:42:30 between the chemiluminescence reaction

00:42:32 that took place here

00:42:33 and what's going on in each of these light sticks

00:42:36 despite the fact that the phenomenon itself is the same.

00:42:39 Chemiluminescence is this phenomenon

00:42:42 that we're talking about

00:42:43 and it's taking place in a liquid phase,

00:42:47 in liquids.

00:42:48 Now each one of you have seen

00:42:50 the phenomenon of chemiluminescence

00:42:52 but not in the liquid phase.

00:42:54 Each one of you have seen chemiluminescence

00:42:57 in the gaseous phase.

00:42:59 What do we call that?

00:43:02 What?

00:43:04 No, neon is not that, no.

00:43:07 Not fluorescence.

00:43:08 You've all seen lightning.

00:43:11 Have you all seen lightning?

00:43:13 That is the phenomenon of chemiluminescence

00:43:15 taking place in the gaseous phase,

00:43:18 not in the liquid phase.

00:43:20 All right, let's go back to the liquid phase

00:43:23 and look at the series of beakers

00:43:26 that we have in front of me here.

00:43:28 We have, how many beakers do we have in the first?

00:43:31 First of all, we have two rows of beakers, right?

00:43:33 We've got 1, 2, 3, 4, 5, 6

00:43:36 and 1, 2, 3, 4, 5, 6.

00:43:39 That sounds like a good number to remember

00:43:42 because what we're going to do next

00:43:44 is mix the contents of the beakers in the back row

00:43:49 with the contents of the beakers in the front row

00:43:52 and see what happens.

00:43:53 So, here we go.

00:43:55 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:00 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:06 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:11 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:17 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:24 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:30 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 10.

00:44:35 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:40 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:44:45 1, 2, 3, 4, 5, 5 and 1 1⁄2, 6.

00:44:50 Six.

00:44:52 All right.

00:44:59 Let's see what happens with the remaining

00:45:02 set of six beakers in the front row and six

00:45:06 beakers in the back row.

00:45:07 All right.

00:45:07 Remember now, magic number is what?

00:45:10 There's really nothing magical about it, right?

00:45:13 Because that depends on how many beakers

00:45:15 I wanted to set up here to begin with

00:45:17 and how fast I wanted it to count.

00:45:19 Right?

00:45:21 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:25 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:30 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:35 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:41 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:47 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:53 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:45:58 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

00:46:05 And...

00:46:07 This is an example of what we call in science a clock reaction.

00:46:18 We call it a clock reaction because the colors appear periodically and they appear at the

00:46:25 same time if the amount of chemicals are the same in each case and if the temperature of

00:46:32 the mixture is the same.

00:46:34 Actually, what I was doing, I was keeping track of time in a very poor way.

00:46:38 I was just counting, right?

00:46:39 I was changing my cadence as we went along.

00:46:42 What's a good way, my way, for keeping time?

00:46:45 What's the best way for keeping time?

00:46:47 What?

00:46:48 Use a clock, right?

00:46:49 That's why we call these a clock reaction and we use a time device, a watch or a clock,

00:46:54 to tell us how fast these colors appear, how fast these reactions appear.

00:47:00 Well, let's move over here and look at a different kind of a reaction.

00:47:08 Before we do that, has anybody been watching this system over here?

00:47:12 Yeah?

00:47:13 Well, come back to it.

00:47:14 Come back and see a lot of interesting things have happened, right?

00:47:17 This has no liquid in it to begin with.

00:47:19 Remember it had a brown gas in it.

00:47:22 This had a colorless liquid in it.

00:47:24 And then this had a pink liquid in it that was rising.

00:47:27 What's happening now?

00:47:29 All kinds of things are happening.

00:47:30 And that is why we do experiments to find out why these different changes take place,

00:47:38 how they take place, what causes them.

00:47:41 And that's really the beauty of doing scientific experiments,

00:47:44 in understanding what makes these reactions.

00:47:47 So just like we like to understand what makes a clock reaction go.

00:47:52 So let's now look at a different set of reactions

00:47:55 that will take place in this large glass beaker

00:48:00 that has a volume of about 4 liters.

00:48:05 I need to plug this in here for just a second.

00:48:08 Okay, I can't plug it in there because the cord is not long enough.

00:48:14 So we'll carry out this reaction.

00:48:26 Right here.

00:48:29 Okay?

00:48:30 Let's plug it in.

00:48:32 Right here.

00:48:34 Okay?

00:48:35 We'll carry out this reaction by mixing chemicals.

00:48:41 That's when a reaction takes place.

00:48:43 You have to mix the chemicals.

00:48:44 If you don't mix them, they just sit back and look at you and don't do anything.

00:48:48 So we have to mix them.

00:48:50 And we're going to mix them in this large beaker.

00:48:53 And we're going to mix them in this large beaker.

00:48:56 And we're going to put a magnetic stirring bar

00:49:03 that is coated with Teflon, another chemical, in there.

00:49:08 And let's see if we can make this spin.

00:49:18 Actually, I'm going to take these out of the way

00:49:21 so I don't knock them accidentally.

00:49:26 I'm sorry I had to disturb the pretty pattern of color to do that,

00:49:30 but that's all right, isn't it?

00:49:34 All right.

00:49:35 Now we're going to take these different chemicals

00:49:39 and mix them

00:49:44 like so.

00:49:51 What do you see happening?

00:49:52 Anything?

00:49:56 Stop.

00:49:57 No, it's still spinning.

00:50:00 The liquid was a little bit cloudy, right?

00:50:05 Looks like a whirlpool.

00:50:06 That's right.

00:50:07 We'll add another chemical.

00:50:11 I'll try to be careful not to splash anything.

00:50:15 Careful as possible.

00:50:16 Anything happening there?

00:50:21 Let's add the third one and see what happens.

00:50:47 Is anything happening?

00:50:51 Lots of interesting things are happening.

00:50:55 Let's stop the stirring and see if that makes a difference.

00:51:03 We see bubbles now.

00:51:06 We see color changes.

00:51:08 What are the color changes?

00:51:21 Is this a clock reaction?

00:51:28 Now remember what happened with the clock reaction.

00:51:31 They changed color and they stayed that color, right?

00:51:36 What's happening here?

00:51:40 The color changes but does not remain the same.

00:51:42 It keeps on changing, right?

00:51:44 Let's mix them again.

00:51:48 See what happens.

00:51:49 More bubbles, right?

00:51:52 There's a gas.

00:51:53 Those are gas bubbles and the gas is being released.

00:51:56 It doesn't dissolve in the liquid very well.

00:51:58 It comes out of the liquid.

00:52:02 This is an example of what we call an oscillating reaction

00:52:06 because the colors oscillate from black or deep blue to black

00:52:12 to colorless, very short period of time colorless,

00:52:15 very short period of time orange,

00:52:17 and then to the deep blue-black color.

00:52:22 It goes on and on for a period of time.

00:52:26 What we try to do in science is try to understand,

00:52:29 first of all, what these mixtures of chemicals are,

00:52:32 why they produce this effect.

00:52:35 Can we change the period of oscillation?

00:52:38 Can we make one color last longer than the other color?

00:52:42 Can we understand why after we mix the chemicals together

00:52:47 that the deep blue-black color now lasts longer

00:52:51 than it did in the beginning?

00:52:53 Did you notice that?

00:52:55 Those are the kinds of questions we ask

00:52:57 when we do scientific experiments.

00:52:59 We're also curious about finding out

00:53:01 why these systems happen.

00:53:03 That's why we do scientific research

00:53:06 at our colleges and universities and in industry.

00:53:11 That's why we try to understand

00:53:13 the fundamental reasons and the fundamental basis

00:53:17 for all these kinds of changes that take place,

00:53:20 not only in this case, but in all the experiments

00:53:23 that I have worked with tonight.

00:53:27 Let's do a couple of more experiments.

00:53:30 As we watch this, we can continue to watch this.

00:53:32 Don't forget now about watching what's going on here.

00:53:34 There's always something going on.

00:53:36 You have to be very attentive to be sure

00:53:38 that you don't get lost in the beautiful colors

00:53:41 that you see all around us.

00:53:44 Let's see if we can do this experiment like so.

00:53:50 What I'm going to do is take this beaker,

00:53:53 which is a one-liter beaker,

00:53:55 and I'm going to take a small amount of powder

00:53:58 out of this bottle and put it in this beaker.

00:54:02 Okay, see it?

00:54:05 There, the powder's at the bottom.

00:54:08 Then I'm going to get some water.

00:54:19 Some liquid water.

00:54:22 Add this, like so.

00:54:27 And as we've learned, before something happens,

00:54:31 we've got to mix, right?

00:54:34 We mix this.

00:54:38 And I thought I added a liquid in there.

00:54:41 You see what has happened?

00:54:44 It has turned into a gel.

00:54:51 See? It's all jelly-like.

00:54:56 Add more water.

00:55:01 You have to be careful now how you mix this,

00:55:06 because it might spill some.

00:55:09 Let's put a little bit of this white substance in here.

00:55:16 And mix it.

00:55:20 And you see it turns into a gel right away.

00:55:25 Now, if we don't understand why these things happen,

00:55:29 that's magic.

00:55:32 If we try to understand why these things happen,

00:55:35 that's science.

00:55:38 That's the beauty of science, trying to understand

00:55:41 why these different things happen.

00:55:44 That is the fun of science, because we have

00:55:47 this intellectual curiosity and great emotional need

00:55:50 to understand and to appreciate these different changes

00:55:53 that take place.

00:55:56 Look at this oscillating reaction.

00:55:59 Is it oscillating anymore?

00:56:02 How come?

00:56:05 It stopped oscillating.

00:56:08 The color changes are no longer repeating themselves.

00:56:11 That's why, as I keep saying,

00:56:14 we do scientific investigations

00:56:17 trying to understand this behavior

00:56:20 and try to get appreciation for the changes that are taking place.

00:56:23 All right, let's take a look now

00:56:26 at this speaker

00:56:29 where I'm going to add two liquids.

00:56:39 Is it going to be what?

00:56:45 Is it going to be loud? I don't know.

00:56:48 How do we find out?

00:56:52 We listen very carefully and we watch.

00:56:57 But if we don't mix the chemicals,

00:57:00 we can be listening for a long time

00:57:03 and nothing happens, right?

00:57:06 So let's find out.

00:57:09 Here's one chemical.

00:57:12 It looks quite syrupy, doesn't it?

00:57:15 Yeah.

00:57:18 And here's the other chemical.

00:57:21 That's syrupy, too.

00:57:24 Is anything happening?

00:57:39 What must happen for a chemical reaction to take place?

00:57:42 We've got to mix the chemicals together, right?

00:57:45 So we mix these chemicals

00:57:48 and that takes effort.

00:57:51 Mixing takes effort.

00:57:54 We stop mixing and look what happens.

00:58:00 Wait a minute, wait a minute.

00:58:18 You remember now when I mixed these things together,

00:58:21 I only mixed a small amount, right?

00:58:24 I mixed what was in these small bottles

00:58:27 and look what has happened.

00:58:30 Lots of interesting things happen when you mix chemicals together.

00:58:33 This is an example

00:58:36 of

00:58:39 something that we call

00:58:42 a polymer.

00:58:45 This polymer is called polyurethane foam.

00:58:48 It's quite solid.

00:58:51 And you notice that I'm touching it

00:58:54 only through my glove

00:58:57 because the chemicals right now

00:59:00 are not terribly friendly to the skin.

00:59:03 It should not be touched by anyone

00:59:06 until three or four hours have passed.

00:59:09 That's why when we finish,

00:59:12 I just want you to see this is pretty hard

00:59:15 and it has a lot of uses

00:59:18 and it also can be harmful

00:59:21 if we don't treat it properly.

00:59:24 So that's one thing that chemists do.

00:59:27 They make some things appear

00:59:30 and you can also take another polymer

00:59:33 which is this polystyrene cup

00:59:36 and

00:59:39 take a little bit of a liquid

00:59:42 you see this?

00:59:45 Take a little bit of a liquid

00:59:48 and put this polystyrene cup in it

00:59:51 and you see the cup

00:59:54 is disappearing.

00:59:57 And that's what

01:00:00 scientists or chemists

01:00:04 scientists or chemists do.

01:00:07 They make certain things appear

01:00:10 and they make certain other things disappear.

01:00:13 Now this, I'll tell you what this is.

01:00:16 This liquid that I use

01:00:19 is called acetone

01:00:22 and everybody's got acetone at home.

01:00:25 Where do you have the acetone at home?

01:00:28 Nail polish remover, that's acetone.

01:00:31 And if you have a polystyrene cup

01:00:34 you can do that.

01:00:37 When you get done, you make sure

01:00:40 that you dispose of this very properly.

01:00:43 And don't dump it down the sink

01:00:46 because it might clog up the sink

01:00:49 especially if not all of it has dissolved.

01:00:52 So actually it's not dissolving

01:00:55 it's just disappearing.

01:00:58 It has air molecules in it

01:01:01 and all we're doing by putting it in acetone

01:01:04 is removing the chlorine from it.

01:01:07 Now, before

01:01:10 before we forget

01:01:13 about chemiluminescence and about combustion

01:01:16 we want to try to do one more experiment

01:01:19 that is really a very interesting experiment.

01:01:22 Well, I don't know if it's really interesting or not

01:01:25 Let's do it and find out if it is.

01:01:28 And to do that I'm going to ask Fred Jurgens

01:01:31 to come up again.

01:01:34 Fred and Judy are going to come up and do this.

01:02:25 There we go.

01:02:28 We've got to work that stuff in with the syringe.

01:02:31 You might see sort of a brownish gas come out of there

01:02:34 when we do that.

01:02:37 That's because one of the gases that's in here

01:02:40 reacts with air to form a brown gas.

01:02:43 The brown gas that's formed is one of the things that's in the smog.

01:02:46 If you've ever been to Los Angeles you know

01:02:49 that the air around there is sort of yellowish.

01:02:52 The smog is formed from the burning

01:02:55 of gasoline and car engines.

01:02:58 When gasoline burns the car engines and gets in the air

01:03:01 the air has nitrogen in it.

01:03:04 And the nitrogen is converted to an oxide of nitrogen which is brown.

01:03:07 Now, we're ready to do this

01:03:10 and what we want to do is get the car gun

01:03:13 one way back

01:03:16 and I'd like to drop it into this thing.

01:03:22 This was

01:03:25 Thank you Fred and Judy.

01:03:28 This was another example

01:03:31 of a chemiluminescent reaction

01:03:34 but it did not last

01:03:37 as long as this reaction did

01:03:40 nor, of course, as long as

01:03:43 these reactions are lasting.

01:03:46 Let's just turn down the volume

01:03:49 and be sure that you recognize

01:03:52 that these reactions are still taking place.

01:03:55 Alright, well the light's up now.

01:03:58 I'm going to try to do

01:04:01 Was that spectacular or not?

01:04:04 Yeah, right.

01:04:07 You know, it's too bad it also has an odor associated with it, right?

01:04:10 I know that because I'm so close to it.

01:04:13 I can tell you that.

01:04:16 Now, this experiment

01:04:19 if we had

01:04:22 slow motion equipment

01:04:25 we could play back that on tape

01:04:28 and look at the flame coming down in slow motion.

01:04:31 Unfortunately, we don't have that tonight

01:04:34 and we'll go on and do the next experiment

01:04:37 which is one that so many of you

01:04:40 may have seen. I'm not sure how many of you

01:04:43 have seen this, but let's try

01:04:46 to do this experiment over here.

01:04:49 This is an experiment.

01:04:52 I'll take the oscillating reaction, what was the oscillating reaction

01:04:55 out of the way.

01:04:58 I'll take the motor out of the way.

01:05:01 I really don't need these eggs here.

01:05:04 How did these eggs end up here?

01:05:07 Because I brought them from over here.

01:05:11 Maybe that's what you're smelling, right?

01:05:14 Okay, what we're going to do now

01:05:17 is take a balloon

01:05:25 blow it up, no big deal, right?

01:05:28 Blow it up, we let some air out

01:05:31 and we tie the balloon

01:05:34 like so.

01:05:40 Oh yeah, what? Some of you are saying, oh yeah.

01:05:43 Okay, now what I'm going to do next

01:05:46 is take a very sharp

01:05:49 needle and I want you to look at this on the monitor.

01:05:52 Look very, very, very carefully at the monitor.

01:05:55 This is very sharp over here, very sharp

01:05:58 and that's why I had this fork on top of it

01:06:01 so as not to hurt myself when I'm using it.

01:06:04 So, I'm going to put some

01:06:07 lubricant on the needle, which is

01:06:10 Vaseline, just ordinary Vaseline.

01:06:13 Lubricate the needle in a very special way, right?

01:06:16 Which way am I doing it? Upward, so I don't

01:06:19 cut myself, right.

01:06:22 Okay, we put this lubricant on the needle.

01:06:25 You can use anything actually you want. You can use oil,

01:06:28 Vaseline, grill cream, whatever you want.

01:06:31 And then

01:06:34 we're going to take this lubricated, sharp needle

01:06:37 and see if we can drive it through

01:06:40 this balloon without puncturing

01:06:43 the balloon. Now, so many of you have your ears

01:06:46 covered. Why do you have your ears covered?

01:06:49 You think this is going to explode like the other balloons

01:06:52 don't, okay. Well, it may or it may not.

01:06:55 Let's try to find out if it will

01:06:58 and let's try to find out if I can actually put the needle

01:07:01 through the balloon, alright, without having it puncture.

01:07:04 So, here we go. Watch the monitor now.

01:07:25 Blow up the balloon. Let some air out.

01:07:28 Tie it up.

01:07:31 Alright.

01:07:34 Get a little lubricant on the needle.

01:07:40 Okay. Take the needle

01:07:43 with the thread. Think I can do it again?

01:07:46 Yeah?

01:07:58 See what's happening

01:08:01 in the first balloon?

01:08:04 It's getting smaller. Why? Because there are holes in it.

01:08:07 Right?

01:08:10 And the air is coming out.

01:08:17 And there's nothing really magical

01:08:20 about these balloons except that they're transparent balloons.

01:08:23 They are latex balloons. I chose those balloons

01:08:27 to show you that there's nothing magical on the inside.

01:08:30 You see, it just pops. Another bang.

01:08:33 Okay? That's not a...

01:08:36 Now, the question is

01:08:39 did you watch very carefully what I was doing?

01:08:42 Yeah? What was I doing?

01:08:45 I put the what?

01:08:48 I put the needle

01:08:56 He said, I put the needle through the thick part.

01:08:59 Now, come on up close here.

01:09:02 Come with me up close on the camera and watch.

01:09:05 You see that this balloon has a thick part right here?

01:09:08 Okay? Next time you blow up a balloon,

01:09:11 look for that thick part.

01:09:14 Every balloon has a thick part.

01:09:17 Almost every balloon has a thick part.

01:09:20 Opposite the place where you blow it.

01:09:23 My hands are full of Vaseline because they're slippery.

01:09:39 Okay, we tie this.

01:09:42 Now, the balloon has two areas that are quite thick.

01:09:45 The one opposite where you blew the balloon

01:09:48 and the one right next to where the mouth of the balloon is.

01:09:52 And if you take the needle very carefully

01:09:55 to lubricate it, it just makes life easier

01:09:58 if you lubricate it.

01:10:01 And you drive this very sharp needle

01:10:04 in the manner that I've done it so far

01:10:07 not through the side of the balloon

01:10:10 but through the thick part.

01:10:13 Want me to try it from the other side now?

01:10:16 Yeah, let's see if that works. Okay.

01:10:19 Now you have to be very careful in aiming at the other end.

01:10:25 There you go.

01:10:37 Now you all think that this is a magic trick, right?

01:10:40 Well, it's not a magic trick.

01:10:43 It's only magic if you don't understand how it's done.

01:10:47 I tried to explain to you very briefly

01:10:50 but very superficially

01:10:53 how I did the experiment.

01:10:56 What we really want to try to think about is

01:10:59 how come when I drive this needle

01:11:02 through the thick part of the balloon

01:11:05 it does not get punctured as it does

01:11:08 when I drive it through the thin part of the balloon.

01:11:11 So we have to think about the properties of this substance

01:11:14 which is latex rubber or ordinary rubber

01:11:17 and try to understand more about the behavior

01:11:20 of that substance

01:11:23 and the behavior of a variety of other substances

01:11:26 in order to explain scientifically

01:11:29 what is going on.

01:11:32 And what I want to do now

01:11:35 is to try to point out to you

01:11:38 all of us, all of you who are curious about

01:11:41 the things that take place in our daily lives

01:11:44 and in our schools

01:11:47 should engage in pursuing your inquiries

01:11:50 with your teachers, with your parents.

01:11:53 You should try to ask questions.

01:11:56 You should try to satisfy your curiosity

01:11:59 as much as possible

01:12:02 because that is really what makes not only life rewarding

01:12:05 but it makes the activities that we engage in

01:12:08 especially the scientific activities that we engage in

01:12:11 fun, as it says on my t-shirt here.

01:12:14 I want to thank you for coming tonight

01:12:17 and I want to wish each one of you not only a Merry Christmas

01:12:20 but Happy Holidays and don't forget to get your present

01:12:23 from Santa Claus as you leave the door tonight.

01:12:26 Thank you very much.

01:12:38 . . .

01:12:41 . .

01:12:44 . .

01:12:47 .

01:12:50 .

01:12:53 .