WEBVTT 1 00:00:18.280 --> 00:00:23.540 Fire can be one of man's worst enemies, or one of his best friends. 2 00:00:24.100 --> 00:00:29.980 To find out about fire, let's talk to a scientist who has devoted his life to it, Dr. Louis 3 00:00:29.980 --> 00:00:38.760 Allen Heard. Dr. Heard? Excuse me, but you startled me. My goodness, doctor, do you 4 00:00:38.760 --> 00:00:44.240 do that often? No, only when I want to let off a little steam. I see. Dr. Heard, just 5 00:00:44.240 --> 00:00:50.740 what is fire? Well, a fire results from a chemical reaction. A fuel unites with 6 00:00:50.740 --> 00:00:58.020 oxygen. Really, we need three things. First, a fuel, then some oxygen, and third, 7 00:00:58.020 --> 00:01:04.100 sufficient heat to get the fire started. If, for instance, I like this piece of 8 00:01:04.100 --> 00:01:10.140 tissue paper, it gets its oxygen from the air and burns up. 9 00:01:16.320 --> 00:01:21.920 But if I take a piece of the same kind of paper and roll it up into a ball, the air 10 00:01:21.920 --> 00:01:35.560 has a hard time getting at it, so we don't get a fire. Now, this block of wood won't 11 00:01:35.560 --> 00:01:41.940 burn very well because it has so little surface exposed to the oxygen. But if we grind up 12 00:01:41.940 --> 00:01:49.740 some wood into some very fine sawdust, such as I have in this tube, and then blow this 13 00:01:49.740 --> 00:01:57.640 sawdust into an open flame, we get some real action. Now, that's what happens in the dust 14 00:01:57.640 --> 00:02:07.680 explosion that you read about. A man found that even oil is hard to burn, so he invented 15 00:02:07.680 --> 00:02:15.780 the wick to expose more of the oil to the air. Now, this wick is made of glass, so it 16 00:02:15.780 --> 00:02:28.580 can't burn. It just increases the surface of the fuel. Nowadays, we do even better. 17 00:02:29.520 --> 00:02:37.220 We spray the oil, and so get many tiny droplets, each surrounded by air. This gives a good 18 00:02:37.220 --> 00:02:46.260 hot flame, as in the oil furnace. Now, if I try to burn this steel bolt, it won't catch 19 00:02:46.260 --> 00:02:51.860 fire, and you didn't expect it would in the first place. But if I take a piece of steel 20 00:02:51.860 --> 00:03:05.940 wool, even steel will catch fire if enough surface is exposed. A fire is a result, really, 21 00:03:05.940 --> 00:03:12.740 of oxidation. But here's an example of an oxidation that does not result in a fire. 22 00:03:17.360 --> 00:03:25.220 It's going on in this mixture of liquids right now. If I say a magic word like petroleum, 23 00:03:26.480 --> 00:03:35.560 now there's an oxidation without flame or smoke. Most fires get their oxygen from the 24 00:03:35.560 --> 00:03:43.560 air, which contains about 20 percent oxygen and 80 percent nitrogen. Now, this flash contains 25 00:03:43.560 --> 00:03:57.000 air, and we see that when the oxygen is all used up, the flame goes out. But if we put 26 00:03:57.000 --> 00:04:03.320 this plant in a flash containing pure oxygen, it will burst at once from just a glow into 27 00:04:03.320 --> 00:04:13.040 a bright flame. To build more useful fires, we sometimes take advantage of several of 28 00:04:13.040 --> 00:04:20.660 these principles. Take magnesium, another metal which burns, brightly but kind of slowly. 29 00:04:26.420 --> 00:04:34.620 To make it burn faster, we do two things. Turn it into a very fine wire to expose more 30 00:04:34.620 --> 00:04:42.640 surface, and then surround it with pure oxygen, and you get a quick, very bright light. That 31 00:04:42.640 --> 00:05:02.660 light has a valuable use. Thank you. Yes, a very valuable use indeed. Now about starting 32 00:05:02.660 --> 00:05:09.900 the fire. Some fuels take fire much more easily than others. Here we are generating a gas 33 00:05:09.900 --> 00:05:23.140 called phospene. The temperature of this room is sufficient to cause it to take fire. It's too bad 34 00:05:23.140 --> 00:05:29.260 we can't use it in cars. We could have automobiles running about blowing smoke rings at each other. 35 00:05:33.220 --> 00:05:41.980 Scientific research can lead to many strange things. Petroleum products can vary from peculiar 36 00:05:41.980 --> 00:05:52.200 stuff like this. The gas, which you can't even see, but which is the most excellent fuel, 37 00:05:53.020 --> 00:05:58.580 and somewhere in between is the ideal fuel for your automobile. Now here is a component 38 00:05:58.580 --> 00:06:08.240 from gasoline that we call heavy ends. We'd like to burn this if we could because it contains lots 39 00:06:08.240 --> 00:06:19.740 of energy, but we can't even ignite it with a match. And here is another fraction from gasoline 40 00:06:19.740 --> 00:06:28.000 that we call light ends, made up of small molecules which readily turn to vapor. We can ignite this 41 00:06:28.000 --> 00:06:40.040 quite easily. So we mix light ends and heavy ends to obtain the perfect blend. A gasoline 42 00:06:40.040 --> 00:06:58.540 which is quick starting, it has lots of power. Speaking of quick starting, here's a convenient 43 00:06:58.540 --> 00:07:02.640 fuel to have around the house when the electricity fails and you don't have a match. 44 00:07:13.200 --> 00:07:15.160 Hmm, something wrong here. 45 00:07:33.380 --> 00:07:35.560 Well, she certainly got a warm personality. 46 00:07:40.740 --> 00:07:49.500 Now here's something that's much like a fire yet isn't a fire. We mix sulfuric acid and table 47 00:07:50.120 --> 00:08:03.420 sugar, and in a moment we see steam and a black char of carbon. 48 00:08:23.580 --> 00:08:30.380 That wasn't quite a fire, but we can burn sugar by mixing it with a substance containing oxygen. 49 00:08:39.460 --> 00:08:48.500 No, no reaction. Well, perhaps we need a catalyst. A catalyst is a substance that speeds up chemical 50 00:08:48.500 --> 00:08:57.660 reactions between other substances. I have here a very powerful catalyst, and I'll add just one 51 00:08:57.660 --> 00:09:17.000 drop of this powerful catalyst to the mixture. The catalyst in this case is water. You may have 52 00:09:17.000 --> 00:09:23.160 another catalyst handy that you don't know about. Suppose we try to burn a lump of table sugar. 53 00:09:28.920 --> 00:09:37.820 It doesn't take fire, but if we add a few cigarette ashes to it, they can't burn. They've already 54 00:09:37.820 --> 00:09:44.960 burned, but they do contain something in the way of a catalyst that lets the sugar burn. 55 00:09:49.780 --> 00:10:00.500 You can try this one yourself. Up to here we've talked about fire, but not about any of the 56 00:10:00.740 --> 00:10:15.440 combustion. If you burn gasoline, for instance, you get water and carbon dioxide. Now here's an 57 00:10:15.440 --> 00:10:30.720 unusual type of combustion. Hydrogen gas uniting with chlorine gas instead of with oxygen. The 58 00:10:30.720 --> 00:10:45.240 I'll get the heat from this infrared lamp. No reaction, so let's try ultraviolet light as a catalyst. 59 00:10:50.100 --> 00:10:58.460 Well, the ultraviolet light caused an ultraviolet reaction. Dr. Hurd, tell me just what is the purpose 60 00:10:58.460 --> 00:11:06.400 of your research on fire? Well, it's very simple. You see, in today's automobiles, it's actually fire 61 00:11:06.400 --> 00:11:14.740 power that drives your car. An eight-cylinder engine at 60 miles an hour builds 9,600 fires 62 00:11:14.740 --> 00:11:21.340 every minute, and each fire must be just right. From this research has come huge catalytic 63 00:11:21.340 --> 00:11:27.600 cracking units. They are one reason why two gallons of today's gasoline do the work that 64 00:11:27.600 --> 00:11:33.080 took three gallons 30 years ago. But now let's relax and blow some soap bubbles. 65 00:12:08.800 --> 00:12:15.140 Funny, but I lose more fingers that way. But I still hope that I can hold a paintbrush. 66 00:12:25.520 --> 00:12:29.240 As usual, fire has the last word.