1 00:00:02,880 --> 00:00:05,320 Early alchemists wrote of a Fountain of Youth, 2 00:00:05,320 --> 00:00:07,960 and for centuries kings and explorers searched 3 00:00:07,960 --> 00:00:10,720 for this legendary spring that would restore the youth 4 00:00:10,720 --> 00:00:12,160 to anyone who drank from it. 5 00:00:15,440 --> 00:00:17,120 Does such a place even exist? 6 00:00:17,120 --> 00:00:19,520 And, if it does, what incredible elements 7 00:00:19,520 --> 00:00:21,160 might we find in its waters? 8 00:00:21,160 --> 00:00:24,120 Join us in the search for the Fountain of Youth. 9 00:00:42,560 --> 00:00:45,120 APPLAUSE 10 00:00:57,360 --> 00:01:00,200 Many people searched for the Fountain of Youth, 11 00:01:00,200 --> 00:01:04,760 but one of the most famous was the 16th Century Spanish explorer 12 00:01:04,760 --> 00:01:06,800 Juan Ponce de Leon, who spent his life 13 00:01:06,800 --> 00:01:08,760 trying to hang onto his good looks. 14 00:01:08,760 --> 00:01:13,120 And legend has it that he found the Fountain in Florida. 15 00:01:13,120 --> 00:01:17,240 Local people claimed this miraculous spring could even restore 16 00:01:17,240 --> 00:01:19,920 frail old men to perfect health 17 00:01:19,920 --> 00:01:22,920 and, incredibly, the spring is still there. 18 00:01:22,920 --> 00:01:25,840 On the screen now we can see the workers 19 00:01:25,840 --> 00:01:29,640 filling bottles from this Fountain of Youth 20 00:01:29,640 --> 00:01:34,240 And they've sent us a sample by airmail. 21 00:01:41,040 --> 00:01:43,640 Here we have our Fountain of Youth. I can't wait. 22 00:01:43,640 --> 00:01:45,440 Right, let's have a look. 23 00:01:49,320 --> 00:01:51,080 "It's on the shelf." OK. 24 00:01:51,080 --> 00:01:55,160 Right, so here it is. They've put it over here. 25 00:01:55,160 --> 00:01:57,200 So here is the Fountain of Youth. 26 00:01:57,200 --> 00:01:59,800 It really has come all the way from Florida 27 00:01:59,800 --> 00:02:02,720 which is quite exciting, but we need somebody to try it. 28 00:02:02,720 --> 00:02:04,880 Do I have a volunteer? Some hands went up... 29 00:02:04,880 --> 00:02:07,400 I'm afraid I can't give it to anyone down the front. 30 00:02:07,400 --> 00:02:08,920 You're far too young already. 31 00:02:08,920 --> 00:02:11,240 If I gave you this, who knows what might happen. 32 00:02:11,240 --> 00:02:14,320 We need somebody slightly more mature, 33 00:02:14,320 --> 00:02:16,160 slightly more advanced in years. 34 00:02:16,160 --> 00:02:19,280 I'm looking at the top, actually, and... 35 00:02:19,280 --> 00:02:21,600 Oh, yes, there's a chap right on the end. 36 00:02:21,600 --> 00:02:23,320 What's your name, please? Tim. 37 00:02:23,320 --> 00:02:25,880 Tim. And you'd like to try some of the Fountain of Youth? 38 00:02:25,880 --> 00:02:27,720 I'll give it a go. You'll give it a go. 39 00:02:27,720 --> 00:02:28,960 That's very good of you. 40 00:02:28,960 --> 00:02:31,760 I think we've arranged for some to be brought up to you. 41 00:02:31,760 --> 00:02:33,800 LAUGHTER 42 00:02:33,800 --> 00:02:36,840 Goodness me. Is it safe? 43 00:02:36,840 --> 00:02:38,400 DR WOTHERS LAUGHS 44 00:02:38,400 --> 00:02:39,880 Well... 45 00:02:44,480 --> 00:02:48,240 Don't drink it all! Save some for later! 46 00:02:48,240 --> 00:02:50,440 So, are you feeling any younger? Not yet. 47 00:02:50,440 --> 00:02:54,120 Not yet? No wrinkles lost yet? Don't know. Don't know. OK. 48 00:02:54,120 --> 00:02:57,960 We'll come back to you later and see how it is going, 49 00:02:57,960 --> 00:03:01,000 but you were very good. You must be a chemistry teacher. 50 00:03:01,000 --> 00:03:02,880 You did ask, "Is it safe to drink?" 51 00:03:02,880 --> 00:03:05,720 You shouldn't be drinking in the chemistry lab, so well done there. 52 00:03:05,720 --> 00:03:07,280 Thank you very much. 53 00:03:07,280 --> 00:03:09,320 A round of applause for Tim for trying our water. 54 00:03:09,320 --> 00:03:11,600 APPLAUSE 55 00:03:15,840 --> 00:03:18,680 This year's Royal Institution Christmas Lectures 56 00:03:18,680 --> 00:03:20,520 are all about the elements. 57 00:03:20,520 --> 00:03:22,600 My name is Dr Peter Wothers, 58 00:03:22,600 --> 00:03:25,200 and I'm a Fellow of The Royal Society of Chemistry. 59 00:03:25,200 --> 00:03:26,880 The ancient Greeks thought 60 00:03:26,880 --> 00:03:30,320 there were just four elements that made up everything around them. 61 00:03:30,320 --> 00:03:33,680 These are the elements earth, air, fire and water. 62 00:03:33,680 --> 00:03:37,080 Last time we looked at the elements in the air, 63 00:03:37,080 --> 00:03:41,680 and tonight we're going to be looking at the elements in a glass of water, 64 00:03:41,680 --> 00:03:45,120 in fact, the water that Tim has just drunk, to be precise. 65 00:03:45,120 --> 00:03:47,840 To help me, we're going to be using our periodic table. 66 00:03:47,840 --> 00:03:50,000 Periodic table. Look at that. Excellent. 67 00:03:50,000 --> 00:03:53,200 Very good, everyone's here. Marvellous. 68 00:03:53,200 --> 00:03:57,080 We now know, of course, that we've got over 100 different elements. 69 00:03:57,080 --> 00:04:02,240 Together, we're going to see what elements we can find in our water 70 00:04:02,240 --> 00:04:05,440 and maybe we're going to find something quite miraculous 71 00:04:05,440 --> 00:04:08,520 in our glass of water, the water that Tim's just drunk. 72 00:04:08,520 --> 00:04:12,960 OK. Right, I need to put on my coat, ready for action now. 73 00:04:12,960 --> 00:04:15,080 So, thank you, periodic table. 74 00:04:17,000 --> 00:04:19,840 Excellent. Oh, you're so well-trained, really! Excellent. 75 00:04:19,840 --> 00:04:22,240 That's perfect, look at that. 76 00:04:22,240 --> 00:04:26,400 So, our periodic table, we saw that there's over 100 elements. 77 00:04:26,400 --> 00:04:30,600 And yet, water, of course, isn't one of these elements. We know this now. 78 00:04:30,600 --> 00:04:34,400 But this was only first realised about 200 years ago, just over. 79 00:04:34,400 --> 00:04:40,560 So, why was that? Well, partly because nobody had ever done this. 80 00:04:41,960 --> 00:04:43,600 BOOMING EXPLOSION 81 00:04:43,600 --> 00:04:45,440 ALL GASP AND GIGGLE 82 00:04:45,440 --> 00:04:47,040 Well! 83 00:04:47,040 --> 00:04:49,280 That seemed to bring the house down! 84 00:04:49,280 --> 00:04:51,120 APPLAUSE 85 00:05:03,000 --> 00:05:05,520 That was certainly rather dramatic! 86 00:05:05,520 --> 00:05:08,800 But what we actually did there is just make some water. 87 00:05:08,800 --> 00:05:11,760 The balloon was filled with hydrogen... 88 00:05:11,760 --> 00:05:14,080 which, of course, when we light it... 89 00:05:14,080 --> 00:05:16,900 combines with the oxygen from the air... 90 00:05:16,900 --> 00:05:18,500 to form water. 91 00:05:20,140 --> 00:05:23,180 OK. Now, that was rather violent, 92 00:05:23,180 --> 00:05:26,140 and we couldn't see any of the water that we made 93 00:05:26,140 --> 00:05:29,580 because as soon as it was made, all that energy that was released there 94 00:05:29,580 --> 00:05:33,660 vaporised it and disbursed all the droplets into the lecture theatre. 95 00:05:33,660 --> 00:05:36,660 But we can do this in a more controlled way, 96 00:05:36,660 --> 00:05:40,060 so we can actually see some of the water being formed. 97 00:05:40,060 --> 00:05:43,780 And, well, this is the apparatus that we're just bringing on now. 98 00:05:43,780 --> 00:05:45,940 OK, so... 99 00:05:45,940 --> 00:05:49,820 We're going to combine our hydrogen and oxygen 100 00:05:49,820 --> 00:05:52,460 in this carefully designed apparatus. 101 00:05:53,620 --> 00:05:56,580 And we're passing pure oxygen through this, 102 00:05:56,580 --> 00:06:01,060 and Mark is just going to pass me a tube with some hydrogen. 103 00:06:04,100 --> 00:06:06,260 And let's just light that. Ah, beautiful. 104 00:06:06,260 --> 00:06:08,540 It's very difficult to see this flame sometimes 105 00:06:08,540 --> 00:06:11,340 because hydrogen burns with more or less a colourless flame. 106 00:06:11,340 --> 00:06:14,180 I think there's a few impurities in the glass there, 107 00:06:14,180 --> 00:06:17,220 but you can see it's definitely lit, it's definitely going. 108 00:06:17,220 --> 00:06:20,500 I'm just going to insert this into the apparatus. 109 00:06:20,500 --> 00:06:23,380 I hope I don't catch fire to our little things there! 110 00:06:23,380 --> 00:06:26,140 There we are, look at that, beautiful, right. 111 00:06:26,140 --> 00:06:27,660 So, just insert this. 112 00:06:27,660 --> 00:06:31,980 In fact, as it's going in, the flame gets much hotter, 113 00:06:31,980 --> 00:06:35,260 because this is an oxygen-rich environment in this apparatus. 114 00:06:35,260 --> 00:06:38,100 And it's just beginning to vaporise some of the glass. 115 00:06:38,100 --> 00:06:40,620 And this yellow colour that you see now 116 00:06:40,620 --> 00:06:43,380 is excited sodium atoms from the glass. 117 00:06:43,380 --> 00:06:46,500 But I'd like everyone to keep an eye on this during the reaction. 118 00:06:46,500 --> 00:06:48,740 This is like our little Olympic flame. 119 00:06:48,740 --> 00:06:52,180 If this goes out, please let me know during the course of the reaction, 120 00:06:52,180 --> 00:06:55,620 I'm trying to generate enough water to maybe taste it later. 121 00:06:55,620 --> 00:06:58,300 We'll have to see, we're using very pure gases here. 122 00:06:58,300 --> 00:07:02,180 The important thing that we can see is that we've got our flame, 123 00:07:02,180 --> 00:07:06,020 it's clearly very hot, but we are generating water. 124 00:07:06,020 --> 00:07:08,820 You can see that this is misting up now at the top here, 125 00:07:08,820 --> 00:07:13,180 and we're beginning to get some water and it's dribbling down here. 126 00:07:13,180 --> 00:07:17,580 So this is actually showing us that water is not an element after all. 127 00:07:17,580 --> 00:07:21,140 It's made up of these two gases, hydrogen and oxygen. 128 00:07:21,140 --> 00:07:25,620 This, as we are forming these bonds here, is releasing a lot of energy. 129 00:07:25,620 --> 00:07:27,300 This is, as we're making new bonds 130 00:07:27,300 --> 00:07:29,420 between hydrogen atoms and oxygen atoms, 131 00:07:29,420 --> 00:07:33,220 forming our droplets of water, that are beginning to collect now. 132 00:07:33,220 --> 00:07:37,740 But I'd like to show you another reaction that clearly generates 133 00:07:37,740 --> 00:07:41,580 a lot of energy, a lot of heat as molecules are coming together, 134 00:07:41,580 --> 00:07:45,100 as bonds are being formed, and this one is quite miraculous. 135 00:07:45,100 --> 00:07:47,220 This is one of my favourite reactions, 136 00:07:47,220 --> 00:07:49,580 because it really does look like magic. 137 00:07:49,580 --> 00:07:52,860 What we've got here is a tube just of cold water. 138 00:07:52,860 --> 00:07:56,140 Everyone knows what temperature water freezes at, don't we? 139 00:07:56,140 --> 00:07:58,020 What temperature does it freeze at? 140 00:07:58,020 --> 00:08:00,020 ALL: Zero. Zero, exactly. 141 00:08:00,020 --> 00:08:04,180 So here it's coming, this is a test tube full of cold water. 142 00:08:04,180 --> 00:08:05,500 Thank you very much. 143 00:08:05,500 --> 00:08:08,540 What temperature is this water at? Minus three. 144 00:08:08,540 --> 00:08:12,220 Minus three, this one. So this is actually at minus three. 145 00:08:12,220 --> 00:08:17,460 And yet, of course, we know that water SHOULD be ice at minus three, 146 00:08:17,460 --> 00:08:19,700 and yet it isn't. OK? 147 00:08:19,700 --> 00:08:23,540 Now, watch what happens when I add just a tiny little crystal of ice. 148 00:08:23,540 --> 00:08:27,620 This is now freezing. OK? 149 00:08:27,620 --> 00:08:32,580 So you can see that this water is turning into ice. 150 00:08:32,580 --> 00:08:35,260 In fact, the ice is all the way down to here now. 151 00:08:36,300 --> 00:08:40,460 So we know that water should be ice at minus three degrees, 152 00:08:40,460 --> 00:08:44,900 and it is now becoming ice at minus three degrees. OK? 153 00:08:44,900 --> 00:08:47,940 In fact, let me see if I can actually turn this upside down. 154 00:08:47,940 --> 00:08:50,580 Can I do that? There's a little bit dribbling out, 155 00:08:50,580 --> 00:08:54,180 but there we are, it is in fact solid ice there. 156 00:08:54,180 --> 00:08:57,580 That's pretty impressive, I think. Let's hand that out, thank you. 157 00:09:00,540 --> 00:09:02,780 Now... How can we...? 158 00:09:04,780 --> 00:09:06,420 So, how can we do this? 159 00:09:06,420 --> 00:09:09,460 We need to be very careful, it's like trying to balance this pen. 160 00:09:09,460 --> 00:09:12,260 I was trying it with a pencil earlier and it didn't work. 161 00:09:12,260 --> 00:09:14,340 I can balance a pen on its end there. 162 00:09:14,340 --> 00:09:16,180 If we're careful, we can do this, 163 00:09:16,180 --> 00:09:18,900 but just give it a small jolt and it falls over. 164 00:09:18,900 --> 00:09:21,460 Now, we can really cool down our water very slowly, 165 00:09:21,460 --> 00:09:24,340 very carefully, we can get it to those temperatures 166 00:09:24,340 --> 00:09:27,540 if it's very, very slowly cooled, really pure water. 167 00:09:27,540 --> 00:09:29,380 But just give it a small jolt, 168 00:09:29,380 --> 00:09:31,980 it starts off this process of being how it should be. 169 00:09:31,980 --> 00:09:35,220 The question now is, what do you think happens to the temperature? 170 00:09:35,220 --> 00:09:36,940 Do you think it stays the same? 171 00:09:36,940 --> 00:09:40,020 Do you think it gets hotter, or do you think it gets colder? 172 00:09:40,020 --> 00:09:43,340 We're going to have a vote. So who thinks it stays the same? 173 00:09:43,340 --> 00:09:46,620 OK, quite a few. Who thinks it gets colder when freezes? 174 00:09:48,100 --> 00:09:50,260 Quite a few of you. And who thinks it gets hotter? 175 00:09:51,500 --> 00:09:53,980 It's a bit of a mix, I think. Let's see what happens. 176 00:09:53,980 --> 00:09:56,540 I need to take this very, very carefully. 177 00:09:56,540 --> 00:10:02,380 And here we can see that the temperature is indeed at -3.7. 178 00:10:02,380 --> 00:10:04,900 This is really pretty good, 179 00:10:04,900 --> 00:10:07,180 in this huge tube here. 180 00:10:07,180 --> 00:10:09,620 I might need some ice, but I'm just going to give this... 181 00:10:09,620 --> 00:10:12,660 Look at that, just moving it has set this off. 182 00:10:12,660 --> 00:10:16,380 Look what's happening to the temperature. It has shot up. 183 00:10:16,380 --> 00:10:21,060 It was at -3.7, it's now just... Well, it's actually, 184 00:10:21,060 --> 00:10:25,660 this top part is now above zero. And again, it's freezing. 185 00:10:25,660 --> 00:10:27,860 This is because as the water molecules... 186 00:10:27,860 --> 00:10:30,060 They were moving around in the liquid, 187 00:10:30,060 --> 00:10:32,780 but as they're locked into place in the ice 188 00:10:32,780 --> 00:10:35,980 we're forming bonds between the water molecules 189 00:10:35,980 --> 00:10:37,620 and the temperature goes up. 190 00:10:37,620 --> 00:10:41,100 That's really beautifully done, it's incredibly difficult to do, 191 00:10:41,100 --> 00:10:44,340 and I think we should thank Fiona for preparing this all day. 192 00:10:44,340 --> 00:10:47,140 Thank you, Fiona. OK, thank you. 193 00:10:55,340 --> 00:10:58,300 So the formation of bonds releases energy. 194 00:10:58,300 --> 00:11:00,180 This is a very important thing. 195 00:11:00,180 --> 00:11:02,620 Now, actually, we can show this in another way. 196 00:11:02,620 --> 00:11:05,980 If you look under your seats, you'll find a little hand warmer. 197 00:11:08,100 --> 00:11:11,580 Now, for those of you, of course, watching at home, I'm afraid, 198 00:11:11,580 --> 00:11:14,820 if you look under your seats, you probably won't find a hand warmer 199 00:11:14,820 --> 00:11:17,420 unless you remembered to put it there earlier, 200 00:11:17,420 --> 00:11:18,740 in which case, well done! 201 00:11:20,100 --> 00:11:23,740 OK, looks like people are finding their hand warmers. 202 00:11:23,740 --> 00:11:26,500 Your hand warmer contains a solution 203 00:11:26,500 --> 00:11:29,020 and it has salts dissolved in this. 204 00:11:29,020 --> 00:11:31,380 But actually, again, it's an unstable situation. 205 00:11:31,380 --> 00:11:34,100 There are more salts dissolved than there should be. 206 00:11:34,100 --> 00:11:36,940 So if we just give this a click, if you haven't done this already, 207 00:11:36,940 --> 00:11:39,380 you just click the little bit of metal in the corner. 208 00:11:39,380 --> 00:11:41,420 That's it, I can hear lots of clicking going on. 209 00:11:41,420 --> 00:11:43,740 That's just starting this reaction now. 210 00:11:43,740 --> 00:11:46,140 EXCITED CHATTER 211 00:11:52,140 --> 00:11:56,180 And it's resorted to exactly how it should be. 212 00:11:56,180 --> 00:12:00,100 We are forming bonds, the salts are precipitating out, 213 00:12:00,100 --> 00:12:03,260 and as they're forming bonds, forming the solid here, 214 00:12:03,260 --> 00:12:06,740 formation of bonds gives out energy and that's what you can feel. 215 00:12:06,740 --> 00:12:11,820 That's what's warming up your hands now, which is rather nice. OK. 216 00:12:11,820 --> 00:12:15,260 So the formation of bonds gives out energy. 217 00:12:15,260 --> 00:12:17,940 And that's what's taking place with our little flame here, 218 00:12:17,940 --> 00:12:19,820 our Olympic flame. 219 00:12:19,820 --> 00:12:22,980 I think we might just turn up the hydrogen a bit, lovely. 220 00:12:22,980 --> 00:12:26,700 So, here we are forming bonds between hydrogen and oxygen 221 00:12:26,700 --> 00:12:28,380 and that's releasing energy. 222 00:12:28,380 --> 00:12:31,140 And this is a really beautiful reaction here, 223 00:12:31,140 --> 00:12:34,420 because the only by-product of this is water. 224 00:12:34,420 --> 00:12:37,460 You may know, of course, when you burn petrol and other fuels, 225 00:12:37,460 --> 00:12:39,900 you get carbon dioxide, this is a greenhouse gas. 226 00:12:39,900 --> 00:12:41,740 The only by-product here is water 227 00:12:41,740 --> 00:12:44,020 and there's a lot of energy being released. 228 00:12:44,020 --> 00:12:48,820 So maybe this could be an answer to the energy problems of the future. 229 00:12:48,820 --> 00:12:50,020 Well, have a look at this. 230 00:12:58,820 --> 00:13:01,020 APPLAUSE 231 00:13:03,060 --> 00:13:06,740 This is Nathan Chang from Valeswood Fuel Cells Ltd. 232 00:13:06,740 --> 00:13:08,980 Nathan, can you tell us, what is this thing? 233 00:13:08,980 --> 00:13:13,220 It looks like a normal road bike. You can put it on the road, can you? 234 00:13:13,220 --> 00:13:15,060 It's a road legal scooter, 235 00:13:15,060 --> 00:13:18,700 but we put the fuel cell and hydrogen on there. 236 00:13:18,700 --> 00:13:21,740 This is lanthanum nickel hydride? 237 00:13:21,740 --> 00:13:24,380 That's a nickel metal-based hydride. 238 00:13:24,380 --> 00:13:26,780 And it's absorbing the hydrogen... Like a sponge. 239 00:13:26,780 --> 00:13:28,860 Like a sponge, and gradually releasing it. 240 00:13:28,860 --> 00:13:31,100 It's combining with the oxygen from the air. 241 00:13:31,100 --> 00:13:33,740 That's giving you the energy to power this bike. 242 00:13:33,740 --> 00:13:36,380 Yeah, that fuel cell generates electricity to power 243 00:13:36,380 --> 00:13:39,020 the motor and power the vehicle. OK, this is great. 244 00:13:39,020 --> 00:13:41,820 So you've just driven all the way through the RI. 245 00:13:41,820 --> 00:13:43,620 Haven't you polluted everywhere, 246 00:13:43,620 --> 00:13:45,940 is there oil dripping out of everything now? 247 00:13:45,940 --> 00:13:49,100 The only emission is water vapour. It's just water vapour. 248 00:13:49,100 --> 00:13:51,100 And the hydrogen comes from water. 249 00:13:51,100 --> 00:13:53,420 The hydrogen itself comes from the water? 250 00:13:53,420 --> 00:13:55,460 So you convert water to hydrogen, 251 00:13:55,460 --> 00:13:57,900 the fuel cell converts hydrogen to water again. 252 00:13:57,900 --> 00:14:00,740 So why don't we see more vehicles like this now? 253 00:14:00,740 --> 00:14:03,820 Why don't we see more hydrogen vehicles? Yeah. 254 00:14:03,820 --> 00:14:06,220 The hydrogen is still very expensive. 255 00:14:06,220 --> 00:14:11,460 And, also, you have problems to store enough hydrogen for a bigger vehicle. 256 00:14:11,460 --> 00:14:13,540 So you'd have to change your tank, would you, 257 00:14:13,540 --> 00:14:15,580 if you wanted to get back to Birmingham? 258 00:14:15,580 --> 00:14:17,980 You'd need a bigger tank. A slightly bigger tank. 259 00:14:17,980 --> 00:14:20,460 That tank can power this vehicle for 70 miles. 260 00:14:20,460 --> 00:14:22,500 70 miles, oh, pretty good then. 261 00:14:22,500 --> 00:14:24,740 So, if we could get a better source of hydrogen, 262 00:14:24,740 --> 00:14:27,620 it would be cheaper, then we'd see more vehicles. Yeah. 263 00:14:27,620 --> 00:14:31,020 Because it's non-polluting, it only produces water, yes? Yeah. 264 00:14:31,020 --> 00:14:34,260 Give Nathan a big round of applause, thank you very much coming in. 265 00:14:34,260 --> 00:14:36,580 APPLAUSE 266 00:14:41,380 --> 00:14:43,340 So we've got a bit of a challenge here. 267 00:14:43,340 --> 00:14:46,620 I mean, hydrogen could be the ideal fuel of the future, 268 00:14:46,620 --> 00:14:50,300 but the problem is, how do we get it in the first place? 269 00:14:50,300 --> 00:14:54,060 And one way that we can get it would be to break up the water. 270 00:14:54,060 --> 00:14:57,260 In fact, Nathan said that the hydrogen that they're using 271 00:14:57,260 --> 00:14:59,860 does come from splitting up water. 272 00:14:59,860 --> 00:15:04,260 But we can see that when hydrogen and oxygen combine to form water, 273 00:15:04,260 --> 00:15:08,220 this gives out a lot of energy. If we want to split up our water 274 00:15:08,220 --> 00:15:11,860 to generate hydrogen and oxygen, we need to put a lot of energy in. 275 00:15:11,860 --> 00:15:15,060 We can show this, this is another general thing of chemistry, 276 00:15:15,060 --> 00:15:16,740 that if we want to break bonds, 277 00:15:16,740 --> 00:15:18,780 we need to put energy into the system, 278 00:15:18,780 --> 00:15:20,780 and we're going to show this first of all 279 00:15:20,780 --> 00:15:23,620 by looking at interactions between water molecules. 280 00:15:23,620 --> 00:15:25,860 I'd like some volunteers from the audience. 281 00:15:25,860 --> 00:15:27,700 The back row, actually. That's it. 282 00:15:27,700 --> 00:15:31,100 Give them all a round of applause. APPLAUSE 283 00:15:37,020 --> 00:15:39,460 In this space, lovely. 284 00:15:39,460 --> 00:15:42,100 Hold up your balloons so everyone can see. That's it. 285 00:15:42,100 --> 00:15:43,940 Now, you're water molecules, OK? 286 00:15:43,940 --> 00:15:46,300 And at the moment you're bonded together 287 00:15:46,300 --> 00:15:48,380 to form the rigid structure of ice. 288 00:15:48,380 --> 00:15:51,820 So, of course, you're going to be wiggling around, gently vibrating. 289 00:15:51,820 --> 00:15:53,300 This is what ice looks like. 290 00:15:53,300 --> 00:15:56,740 But if we give them more energy, we can break some of these bonds 291 00:15:56,740 --> 00:15:59,700 that hold the water molecules together, and we get liquid. 292 00:15:59,700 --> 00:16:03,020 Now you can start moving around. Just have a little walk. 293 00:16:03,020 --> 00:16:05,340 This is our liquid. In fact, on the screen now, 294 00:16:05,340 --> 00:16:08,060 we can see this is a very complicated calculation 295 00:16:08,060 --> 00:16:11,220 carried out at the University of Cambridge from scratch. 296 00:16:11,220 --> 00:16:14,780 This shows what happens when liquid water molecules get together. 297 00:16:14,780 --> 00:16:16,460 They're jiggling around, 298 00:16:16,460 --> 00:16:18,900 but they are sort of held more or less in place 299 00:16:18,900 --> 00:16:21,060 with these dotted lines that you see there. 300 00:16:21,060 --> 00:16:23,460 These are bonds called hydrogen bonds. 301 00:16:23,460 --> 00:16:25,740 This is where the oxygen of one water molecule 302 00:16:25,740 --> 00:16:28,020 is slightly negatively charged, and it sticks 303 00:16:28,020 --> 00:16:31,260 to the slightly positively charged hydrogen of the other. 304 00:16:31,260 --> 00:16:32,460 Keep walking around. 305 00:16:32,460 --> 00:16:35,940 But what happens if we give you even MORE energy? 306 00:16:35,940 --> 00:16:37,580 They start separating, 307 00:16:37,580 --> 00:16:40,540 and we can get them to fly out into the audience here. 308 00:16:40,540 --> 00:16:43,060 This is where we're making steam, all right? 309 00:16:43,060 --> 00:16:45,100 LAUGHTER So lots more energy, 310 00:16:45,100 --> 00:16:49,540 the water molecules are separated, and we've got steam. 311 00:16:49,540 --> 00:16:51,500 So thank you very much, water molecules. 312 00:16:51,500 --> 00:16:53,300 Please return to your seats. 313 00:16:53,300 --> 00:16:55,420 APPLAUSE 314 00:16:59,460 --> 00:17:02,340 So, all we've managed to achieve so far, then, 315 00:17:02,340 --> 00:17:06,660 is pulling the water molecules apart from each other to generate steam. 316 00:17:06,660 --> 00:17:09,300 But this raises a very interesting question - 317 00:17:09,300 --> 00:17:12,780 how much more space does the steam now take up, 318 00:17:12,780 --> 00:17:14,260 compared to the water? 319 00:17:14,260 --> 00:17:17,580 So, in other words, if I took one millilitre of water, 320 00:17:17,580 --> 00:17:20,820 how many millilitres of steam would I be able to get? 321 00:17:20,820 --> 00:17:24,300 This piece of apparatus here is designed to try and show us 322 00:17:24,300 --> 00:17:27,540 how much steam we can get from one millilitre of water. 323 00:17:27,540 --> 00:17:30,980 And I need a volunteer for this one, please. Er... 324 00:17:30,980 --> 00:17:32,460 yes, actually, in the white. 325 00:17:32,460 --> 00:17:35,500 Would you like to come down to the front, please? 326 00:17:35,500 --> 00:17:37,780 APPLAUSE 327 00:17:40,540 --> 00:17:43,180 OK. And your name is? Connor. Connor, OK, great. 328 00:17:43,180 --> 00:17:44,940 Do you know how many millilitres of steam 329 00:17:44,940 --> 00:17:46,540 we're going to get from 1ml of water? 330 00:17:46,540 --> 00:17:48,660 Have a guess. You've got a scale here. 331 00:17:48,660 --> 00:17:50,500 You're going to be looking at this scale. 332 00:17:50,500 --> 00:17:53,540 It goes from zero up to 100ml. How many do you think? 333 00:17:53,540 --> 00:17:54,980 50. 50 ml. 334 00:17:54,980 --> 00:17:59,020 In the middle, OK. Who thinks more than 50? 335 00:17:59,020 --> 00:18:01,100 Who thinks less than 50? 336 00:18:01,100 --> 00:18:02,780 More than 50? 337 00:18:02,780 --> 00:18:04,100 Yes? 100. 338 00:18:04,100 --> 00:18:05,740 100. Any advances on 100? 339 00:18:05,740 --> 00:18:08,380 Yes? 150. Well, if it goes past 100... 340 00:18:08,380 --> 00:18:11,620 150 is going to be past the dial. I want you to watch the dial. 341 00:18:11,620 --> 00:18:14,300 I'm going to squirt the water in this end. 342 00:18:14,300 --> 00:18:17,620 Here's my syringe. So this is going to be 1ml of water. 343 00:18:17,620 --> 00:18:20,300 I'm hoping that this is all nice and hot. 344 00:18:20,300 --> 00:18:22,340 So 1ml is not a lot. 345 00:18:22,340 --> 00:18:25,860 If you see, that's just 1ml there. and you think 50, don't you? 346 00:18:25,860 --> 00:18:28,700 And we've got all sorts of different guesses here. 347 00:18:28,700 --> 00:18:32,540 So, right, I'm just going to turn this tap and put this in, 348 00:18:32,540 --> 00:18:35,540 and I hope, fingers crossed, I squirt that in, 349 00:18:35,540 --> 00:18:38,020 close the tap, and there we are. 350 00:18:38,020 --> 00:18:40,660 Watch the thing. Let's see how far it's going to go... 351 00:18:40,660 --> 00:18:42,860 Keep going. 50... oh, it's gone past your 50. 352 00:18:42,860 --> 00:18:44,540 Still going. It's gone past 75. 353 00:18:44,540 --> 00:18:46,940 Can we turn this on actually? Is that possible? 354 00:18:46,940 --> 00:18:50,500 To get this back up to temperature? MACHINE WHIRS 355 00:18:50,500 --> 00:18:53,540 Ah, brilliant! Yeah, I can see it boiling now. 356 00:18:53,540 --> 00:18:56,620 So we're trying to get some heat back into this thing. 357 00:18:56,620 --> 00:18:59,220 How far have we gone so far? 225. 358 00:18:59,220 --> 00:19:00,540 Sorry? How many? 225. 359 00:19:00,540 --> 00:19:01,980 225. Who said 225? 360 00:19:01,980 --> 00:19:03,140 Oh, well done! 361 00:19:03,140 --> 00:19:06,260 Well, we've gone past that now! LAUGHTER 362 00:19:06,260 --> 00:19:08,700 Right, OK, it's still going. Got quite a lot of... 363 00:19:08,700 --> 00:19:10,780 look down this end, actually. 364 00:19:10,780 --> 00:19:12,900 Yeah, you can see the water in there. 365 00:19:12,900 --> 00:19:15,860 Yeah, still quite a lot. Oh, you've missed the dial! 366 00:19:15,860 --> 00:19:17,420 How's he doing? What's that? 367 00:19:17,420 --> 00:19:19,020 300. 300, OK. Good, keep going. 368 00:19:19,020 --> 00:19:21,860 Still water there. It's still going, then. We're up to... 369 00:19:21,860 --> 00:19:23,900 What are we up to? 450. 370 00:19:23,900 --> 00:19:25,900 450, OK. Not quite hot enough. 371 00:19:25,900 --> 00:19:28,820 It's so difficult to do this. It needs to be SO hot. 372 00:19:28,820 --> 00:19:30,420 Where are we up to now? 650. 373 00:19:30,420 --> 00:19:31,940 650? We're still going. 374 00:19:31,940 --> 00:19:34,180 There's still quite a bit of water there. 375 00:19:34,180 --> 00:19:36,940 This is just our 1ml. 376 00:19:36,940 --> 00:19:39,980 OK. And this is now... Where are we up to? 377 00:19:39,980 --> 00:19:41,820 900. 900. 378 00:19:41,820 --> 00:19:44,580 So quite a few people said...oh, is that 1,000? 379 00:19:44,580 --> 00:19:46,060 Yeah. That's 1,000, OK. 380 00:19:46,060 --> 00:19:48,220 Now, it's still expanding. 381 00:19:48,220 --> 00:19:49,740 We'll keep counting here. 382 00:19:49,740 --> 00:19:54,220 But this is actually really quite important, this expansion here. 383 00:19:54,220 --> 00:19:57,620 It's THIS expansion that drove, quite literally, 384 00:19:57,620 --> 00:19:59,500 the Industrial Revolution. 385 00:19:59,500 --> 00:20:03,540 It was the power here, as water is turned into steam, 386 00:20:03,540 --> 00:20:06,140 driving pistons, driving our machinery. 387 00:20:06,140 --> 00:20:07,780 How are we up to so far? 388 00:20:07,780 --> 00:20:11,020 1,375. 1,375. Very precise! 389 00:20:11,020 --> 00:20:13,140 You're a keen scientist, I can tell! 390 00:20:13,140 --> 00:20:14,900 Physicist. Physicist! Ah! 391 00:20:14,900 --> 00:20:17,900 Almost as good as a chemist! LAUGHTER 392 00:20:17,900 --> 00:20:20,660 Anyway, how are we doing now? This is coming up to... 1,650. 393 00:20:20,660 --> 00:20:23,140 1,650. OK, we're going to have to stop this now. 394 00:20:23,140 --> 00:20:27,300 There's a tiny bit there, but this is going to go to over 2,000ml. 395 00:20:27,300 --> 00:20:31,980 So, you're a physicist, and you said, what was it? 50ml?! 396 00:20:31,980 --> 00:20:34,020 Well, anyway, thank you very much. 397 00:20:34,020 --> 00:20:37,180 Give him a big round of applause for keeping track. Thank you. 398 00:20:37,180 --> 00:20:39,260 APPLAUSE 399 00:20:41,740 --> 00:20:43,780 So, we've converted our water into steam, 400 00:20:43,780 --> 00:20:46,340 and we need to put quite a lot of energy in to do that, 401 00:20:46,340 --> 00:20:48,980 but we still haven't actually made our hydrogen. 402 00:20:48,980 --> 00:20:50,460 This is what we were trying to do. 403 00:20:50,460 --> 00:20:53,820 To do that, to actually split apart the water molecules, 404 00:20:53,820 --> 00:20:56,340 we need to put even more energy into them. 405 00:20:56,340 --> 00:20:59,700 And, we're going to show this now with this apparatus. 406 00:20:59,700 --> 00:21:01,940 So we've got some water in the tubes here, 407 00:21:01,940 --> 00:21:03,700 and I'm just going to plug this in. 408 00:21:03,700 --> 00:21:05,860 So this is connected to here, 409 00:21:05,860 --> 00:21:08,700 and this is a generator. 410 00:21:08,700 --> 00:21:10,740 So if I hop on the bike, 411 00:21:10,740 --> 00:21:16,820 I should be able to drive the little generator at the back like this. 412 00:21:16,820 --> 00:21:18,660 We can begin to see some bubbles. 413 00:21:18,660 --> 00:21:21,540 It's quite hard work here, trying to split up the water, 414 00:21:21,540 --> 00:21:24,780 so I'm going to get somebody else to do all the hard work, I think. 415 00:21:24,780 --> 00:21:27,420 Actually, we need quite a lot of hydrogen, 416 00:21:27,420 --> 00:21:29,540 so I'd like you to welcome, please, 417 00:21:29,540 --> 00:21:32,100 Paralympic gold medallist, Mark Colbourne. 418 00:21:32,100 --> 00:21:33,900 Thank you very much, Mark. 419 00:21:33,900 --> 00:21:36,820 APPLAUSE AND CHEERING 420 00:21:38,820 --> 00:21:41,020 Thank you for joining us. Thank you very much. 421 00:21:44,580 --> 00:21:48,140 LOUD APPLAUSE AND CHEERING 422 00:21:51,860 --> 00:21:54,300 Some great warmth from the audience here. 423 00:21:54,300 --> 00:21:56,260 You've obviously done a fantastic job. 424 00:21:56,260 --> 00:21:59,740 Before you get onto this thing, tell us a little bit about yourself. 425 00:21:59,740 --> 00:22:02,180 You had an accident paragliding, is that right? 426 00:22:02,180 --> 00:22:04,860 I did, yes. May 2009. 427 00:22:04,860 --> 00:22:07,220 So just over three and half years ago. 428 00:22:07,220 --> 00:22:10,700 I broke my back in a near fatal paragliding crash in South Wales. 429 00:22:10,700 --> 00:22:12,940 So I was very lucky to survive, yeah. 430 00:22:12,940 --> 00:22:16,180 And clearly it's not affected your legs too much, 431 00:22:16,180 --> 00:22:18,020 since you can cycle so well! 432 00:22:18,020 --> 00:22:21,660 Yes, I've been left with lower leg paralysis. 433 00:22:21,660 --> 00:22:25,340 So both my feet don't work, so I have to wear special ankle supports. 434 00:22:25,340 --> 00:22:28,980 No hamstrings firing, no bum muscles firing, so it's all quads. 435 00:22:28,980 --> 00:22:31,940 There's pretty big quads there, so that's pretty good! 436 00:22:31,940 --> 00:22:33,820 Now, this is what I'd like to see. Yes! 437 00:22:33,820 --> 00:22:37,420 Being a modern alchemist, this is some gold, is it? Some real gold? 438 00:22:37,420 --> 00:22:41,860 Yes, what you have here is my very own Paralympic gold medal. 439 00:22:41,860 --> 00:22:43,860 That's fantastic. 440 00:22:43,860 --> 00:22:47,420 APPLAUSE AND CHEERING 441 00:22:51,220 --> 00:22:53,140 This certainly feels pretty heavy. 442 00:22:53,140 --> 00:22:54,780 Is this solid gold? 443 00:22:54,780 --> 00:22:58,620 No, it's actually 390g of solid silver, 444 00:22:58,620 --> 00:23:00,620 and then you have 22g of gold 445 00:23:00,620 --> 00:23:03,300 obviously coated around the outside, 446 00:23:03,300 --> 00:23:06,540 and, proudly, actually made in Llantrisant, in South Wales. 447 00:23:06,540 --> 00:23:08,540 Oh, that's fantastic. Really good. 448 00:23:08,540 --> 00:23:11,020 Nice to see a bit of gold in the studio, as well. 449 00:23:11,020 --> 00:23:14,060 I think we've got a picture of you here, just crossing the line. 450 00:23:14,060 --> 00:23:16,620 How did it feel crossing the line? Just euphoric. 451 00:23:16,620 --> 00:23:19,580 It was almost like Christmas and birthdays rolled into one. 452 00:23:19,580 --> 00:23:22,620 And you got one of these, as well. Fantastic. Very much so. 453 00:23:22,620 --> 00:23:25,460 But have you ever split up any water molecules before? 454 00:23:25,460 --> 00:23:28,100 That's the real question. No, not in this sense! 455 00:23:28,100 --> 00:23:30,700 Obviously, lots of sweat when I'm training. 456 00:23:30,700 --> 00:23:32,340 I think you need to give it a go. 457 00:23:32,340 --> 00:23:35,220 If you'd like to hop on. I'll look after this for you. 458 00:23:35,220 --> 00:23:37,300 OK, wonderful. Make sure he doesn't run away, OK? 459 00:23:37,300 --> 00:23:38,620 LAUGHTER 460 00:23:38,620 --> 00:23:40,700 Because I won't be able to catch him! 461 00:23:40,700 --> 00:23:45,020 Yes, so, now then, Mark's on this bike here. 462 00:23:45,020 --> 00:23:49,180 All his power is going to go into driving this little generator here, 463 00:23:49,180 --> 00:23:51,460 and this really is just connected 464 00:23:51,460 --> 00:23:54,020 to the water we've got in these tubes. 465 00:23:54,020 --> 00:23:56,340 OK, take it away then. That's great. 466 00:23:56,340 --> 00:23:58,220 So we've got two electrodes here. 467 00:23:58,220 --> 00:24:00,060 On the negative electrode, 468 00:24:00,060 --> 00:24:03,500 this is where the hydrogen atoms are collecting. 469 00:24:03,500 --> 00:24:06,660 So, remember, the hydrogen in the water is slightly positive, 470 00:24:06,660 --> 00:24:09,420 the negative electrode is giving them electrons, 471 00:24:09,420 --> 00:24:12,660 forming hydrogen atoms, and forming hydrogen molecules. 472 00:24:12,660 --> 00:24:14,820 On the positive electrode, the oxygen atoms, 473 00:24:14,820 --> 00:24:17,020 which are slightly negative in the water, 474 00:24:17,020 --> 00:24:19,260 are having those extra electrons ripped away 475 00:24:19,260 --> 00:24:22,540 to form oxygen atoms and, eventually, oxygen molecules. 476 00:24:22,540 --> 00:24:25,340 But the interesting thing here, as Mark's pedalling away... 477 00:24:25,340 --> 00:24:27,180 Go on, faster! 478 00:24:27,180 --> 00:24:29,540 The interesting thing is that we can clearly see 479 00:24:29,540 --> 00:24:32,420 that we're getting twice as much hydrogen gas 480 00:24:32,420 --> 00:24:34,380 as we are getting oxygen gas. 481 00:24:34,380 --> 00:24:36,100 So this clearly shows, then, 482 00:24:36,100 --> 00:24:39,380 that water is made up of twice as much hydrogen as oxygen. 483 00:24:39,380 --> 00:24:41,340 Oh, I think you've broken it! Go slower! 484 00:24:41,340 --> 00:24:42,980 Has it gone again? Sorry! 485 00:24:42,980 --> 00:24:45,780 Pretty tiring, isn't it? Don't you think? 486 00:24:45,780 --> 00:24:48,100 Pretty tough. Yeah, thank you very much. 487 00:24:48,100 --> 00:24:50,500 I think a big round of applause there for Mark. 488 00:24:50,500 --> 00:24:53,540 APPLAUSE AND CHEERING 489 00:24:55,020 --> 00:24:57,980 Perhaps...can I offer you a drink afterwards? 490 00:24:57,980 --> 00:25:00,700 Do you need a drop of water after that? Yes, definitely. 491 00:25:00,700 --> 00:25:02,500 Lots of water. Would you want this? 492 00:25:02,500 --> 00:25:04,220 This is our Fountain of Youth. 493 00:25:04,220 --> 00:25:06,660 In fact, we've got a guinea pig trying this. 494 00:25:06,660 --> 00:25:08,020 Tim, how's it going? 495 00:25:08,020 --> 00:25:10,260 How's your Fountain of Youth? Just the same. 496 00:25:10,260 --> 00:25:13,300 Don't feel any different at all. No wrinkles gone yet? 497 00:25:13,300 --> 00:25:16,060 No, still there! OK, we'll come back. 498 00:25:16,060 --> 00:25:19,180 We'll give it a chance later. But, anyway, thank you very much. 499 00:25:19,180 --> 00:25:21,580 I'll give that one to you. Thank you for coming. 500 00:25:21,580 --> 00:25:22,740 Thank you. Cheers. 501 00:25:22,740 --> 00:25:25,460 APPLAUSE AND CHEERING 502 00:25:29,140 --> 00:25:31,980 So, we've seen, then, that we need to put energy in 503 00:25:31,980 --> 00:25:33,260 to split up our water. 504 00:25:33,260 --> 00:25:35,780 And a lot of energy is needed there, 505 00:25:35,780 --> 00:25:38,620 and I don't think that using Olympic cyclists... 506 00:25:38,620 --> 00:25:42,100 Even Britain doesn't have enough Olympic gold medal cyclists 507 00:25:42,100 --> 00:25:45,580 to power all the vehicles in the future using hydrogen. 508 00:25:45,580 --> 00:25:47,460 But there is another way of doing this. 509 00:25:47,460 --> 00:25:52,100 Our plants here use the energy from sunlight to split up water. 510 00:25:52,100 --> 00:25:54,500 They spit out oxygen during the daytime, of course, 511 00:25:54,500 --> 00:25:56,220 but they're using the hydrogen 512 00:25:56,220 --> 00:25:58,580 to build up the molecules they're made from. 513 00:25:58,580 --> 00:26:00,820 So maybe we can learn from nature. 514 00:26:00,820 --> 00:26:05,860 Now, Professor Akihiko Kudo from the Tokyo University of Science 515 00:26:05,860 --> 00:26:09,180 has worked on a catalyst here. 516 00:26:09,180 --> 00:26:12,380 This is really quite remarkable stuff. This is quite cutting edge. 517 00:26:12,380 --> 00:26:14,820 This is a catalyst that can use 518 00:26:14,820 --> 00:26:18,060 the energy of light to split up water. 519 00:26:18,060 --> 00:26:20,260 And the catalyst is made of... 520 00:26:20,260 --> 00:26:23,620 Well, actually, if we can just have our periodic tables up for a moment. 521 00:26:23,620 --> 00:26:25,220 Very good, periodic tables! 522 00:26:25,220 --> 00:26:28,660 OK, this catalyst is made up of the element sodium. 523 00:26:28,660 --> 00:26:30,260 Sodium, give us a little wave! 524 00:26:30,260 --> 00:26:32,100 There we are. Very good, sodium. 525 00:26:32,100 --> 00:26:33,940 OK, can you see sodium there? 526 00:26:33,940 --> 00:26:37,580 And we've got tantalum, right in the centre. Very good, tantalum. 527 00:26:37,580 --> 00:26:40,420 And oxygen up there. So this is sodium tantalate, 528 00:26:40,420 --> 00:26:43,460 and it's doped with lanthanum. Where's lanthanum? 529 00:26:43,460 --> 00:26:44,860 There's lanthanum. Very good. 530 00:26:44,860 --> 00:26:46,740 Give us a little wave at the top there. 531 00:26:46,740 --> 00:26:49,700 So this is the catalyst that he's developed, 532 00:26:49,700 --> 00:26:52,340 and this will convert the energy from light 533 00:26:52,340 --> 00:26:54,700 and use this energy to split up water. 534 00:26:54,700 --> 00:26:56,260 So, at ease, periodic tables! 535 00:26:56,260 --> 00:26:57,900 Back down, thank you very much. 536 00:26:57,900 --> 00:27:00,180 OK, so are we ready? Yep. 537 00:27:00,180 --> 00:27:03,980 OK, now, we're just going to put this on, then. 538 00:27:05,380 --> 00:27:08,420 OK, now, so this is the catalyst, 539 00:27:08,420 --> 00:27:11,780 sodium tantalate doped with lanthanum, 540 00:27:11,780 --> 00:27:15,140 and we're shining UV light on this, 541 00:27:15,140 --> 00:27:18,220 and, yes, I can see some bubbles. 542 00:27:18,220 --> 00:27:22,340 There are some bubbles in the upper part of the chamber there. 543 00:27:22,340 --> 00:27:24,820 If we just move up, we can see some. There we are. 544 00:27:24,820 --> 00:27:28,260 This is bubbles forming. So, as I say, this is quite remarkable. 545 00:27:28,260 --> 00:27:33,220 This is using light energy to catalytically split up, 546 00:27:33,220 --> 00:27:35,180 so this is not changing the catalyst, 547 00:27:35,180 --> 00:27:39,940 but it's splitting up water into hydrogen gas and oxygen gas. 548 00:27:39,940 --> 00:27:42,380 So we can see these bubbles here. 549 00:27:42,380 --> 00:27:44,860 Now, unfortunately, the slight snag with this one 550 00:27:44,860 --> 00:27:49,340 is that it's using ultraviolet light and not just visible light. 551 00:27:49,340 --> 00:27:51,740 The plants, of course, use visible light. 552 00:27:51,740 --> 00:27:53,780 But scientists all round the world 553 00:27:53,780 --> 00:27:55,860 are trying to work on developing a catalyst 554 00:27:55,860 --> 00:27:59,300 that will work very efficiently with visible light instead. 555 00:27:59,300 --> 00:28:01,300 And if you can do that... 556 00:28:01,300 --> 00:28:03,340 Well, maybe somebody from the audience 557 00:28:03,340 --> 00:28:05,940 will be the scientist that actually finds a catalyst 558 00:28:05,940 --> 00:28:07,820 that will work with visible light. 559 00:28:07,820 --> 00:28:10,420 And if you can do that, you're going to be very rich, 560 00:28:10,420 --> 00:28:14,300 and you will help to solve the world's energy problems. 561 00:28:14,300 --> 00:28:18,820 Right, so, I think it's time that we actually checked the water, 562 00:28:18,820 --> 00:28:20,980 after all this time making it. 563 00:28:20,980 --> 00:28:23,380 So we had to take a lot of precautions here, 564 00:28:23,380 --> 00:28:25,540 to ensure that this really is extra pure. 565 00:28:25,540 --> 00:28:27,900 This is something you should NEVER normally do 566 00:28:27,900 --> 00:28:29,580 during any science experiment. 567 00:28:29,580 --> 00:28:31,940 You shouldn't drink the products of the reaction. 568 00:28:31,940 --> 00:28:34,820 But this apparatus has been specially designed for this. 569 00:28:34,820 --> 00:28:37,180 We've used extra pure oxygen, medical oxygen, 570 00:28:37,180 --> 00:28:39,420 we've used extra pure hydrogen here. 571 00:28:39,420 --> 00:28:42,860 So I am actually going to just try a few drops of this. 572 00:28:48,020 --> 00:28:50,620 Actually, it doesn't taste too nice, to be honest! 573 00:28:50,620 --> 00:28:51,860 LAUGHTER 574 00:28:51,860 --> 00:28:54,740 But it's basically just pure water. 575 00:28:54,740 --> 00:28:57,380 And Tim was using the Fountain of Youth water. 576 00:28:57,380 --> 00:28:59,900 If we look on the bottle of the Fountain of Youth water, 577 00:28:59,900 --> 00:29:02,460 we see there are other minerals dissolved in it. 578 00:29:02,460 --> 00:29:05,220 This is, of course, because water is a very good solvent - 579 00:29:05,220 --> 00:29:06,500 things dissolve in it - 580 00:29:06,500 --> 00:29:09,860 and, well, look at all the other components in our water. 581 00:29:09,860 --> 00:29:12,380 We've got, for instance, there's a lot of calcium, 582 00:29:12,380 --> 00:29:14,340 there's quite a lot of calcium there. 583 00:29:14,340 --> 00:29:16,940 There's quite a bit of sodium in this, as well. 584 00:29:16,940 --> 00:29:18,580 So, sodium, what's your symbol? 585 00:29:18,580 --> 00:29:20,260 SODIUM: Na! 586 00:29:20,260 --> 00:29:24,260 OK, and do you have Na idea where this comes from? 587 00:29:24,260 --> 00:29:25,780 Where does this symbol come from? 588 00:29:25,780 --> 00:29:27,380 Any ideas? No? No? OK. 589 00:29:27,380 --> 00:29:29,020 Well, I'm going to show you. 590 00:29:29,020 --> 00:29:31,860 Hold the sign up, please, so we can all see. That's it. 591 00:29:31,860 --> 00:29:33,580 So, Na, where does this come from? 592 00:29:33,580 --> 00:29:35,540 Well, actually, I have a book here. 593 00:29:35,540 --> 00:29:37,740 Thank you. Now, in the book, 594 00:29:37,740 --> 00:29:41,020 we can see that this is a chap... 595 00:29:41,020 --> 00:29:44,300 This book is from 1557, 596 00:29:44,300 --> 00:29:47,740 and this man here, he's making piles of compound here, 597 00:29:47,740 --> 00:29:50,180 and this is actually sodium carbonate. 598 00:29:50,180 --> 00:29:52,820 They called it natron or niter. And this is... 599 00:29:52,820 --> 00:29:56,260 He's taking Nile water here, so this is water from the Nile, 600 00:29:56,260 --> 00:29:59,660 and this is why it's called niter, from the Nile water. 601 00:29:59,660 --> 00:30:01,620 This corrupted into natron, 602 00:30:01,620 --> 00:30:04,780 and this is the word that gives us the symbol for sodium. 603 00:30:04,780 --> 00:30:07,620 Na comes from the Latin version of this, natrium. 604 00:30:07,620 --> 00:30:09,860 But it was first discovered in water. 605 00:30:09,860 --> 00:30:12,740 OK, thank you. So, periodic table, at ease. 606 00:30:12,740 --> 00:30:15,340 Thank you. Now, how was this detected? 607 00:30:15,340 --> 00:30:18,980 Because we can't see any of these substances in water, 608 00:30:18,980 --> 00:30:21,860 because they're present in such small quantities, 609 00:30:21,860 --> 00:30:25,220 we have to use a chemist's technique called spectroscopy. 610 00:30:25,220 --> 00:30:29,180 And this looks at how energy interacts with electrons in atoms. 611 00:30:29,180 --> 00:30:32,140 Give them some energy, they move up, and as they drop back down again, 612 00:30:32,140 --> 00:30:34,940 they can give out this energy as light. 613 00:30:34,940 --> 00:30:39,740 And each element has its own unique, characteristic, unique colours. 614 00:30:39,740 --> 00:30:43,980 It has its own spectrum, like a rainbow barcode for each element. 615 00:30:43,980 --> 00:30:47,020 And we're going to show this now with all these symbols here. 616 00:30:47,020 --> 00:30:49,220 These are the symbols from group 1 elements. 617 00:30:49,220 --> 00:30:51,980 Can we have group 1 only, please? That's it. Put them up. 618 00:30:51,980 --> 00:30:55,340 Hydrogen, well, you are, of course, a component of water. 619 00:30:55,340 --> 00:30:57,940 You're not really IN water, dissolved in it, 620 00:30:57,940 --> 00:30:59,820 so you can put your card down. 621 00:30:59,820 --> 00:31:02,060 Francium, I'm afraid you're too radioactive, 622 00:31:02,060 --> 00:31:04,500 so there's going to be no francium in our water, 623 00:31:04,500 --> 00:31:06,340 so you can put your card down, as well. 624 00:31:06,340 --> 00:31:09,700 But these other group 1 elements, well, here they are here. 625 00:31:09,700 --> 00:31:12,020 We've actually taken some symbols here 626 00:31:12,020 --> 00:31:14,660 and soaked each of these symbols with salts. 627 00:31:14,660 --> 00:31:17,220 With compounds of the appropriate elements. 628 00:31:17,220 --> 00:31:19,500 And watch what happens when we light them. 629 00:31:37,580 --> 00:31:40,860 APPLAUSE 630 00:31:47,980 --> 00:31:51,380 We can certainly see that the sodium and lithium are very different, 631 00:31:51,380 --> 00:31:53,220 but these ones look rather similar. 632 00:31:53,220 --> 00:31:54,660 But, actually, they're not. 633 00:31:54,660 --> 00:31:56,460 If we were to look very closely 634 00:31:56,460 --> 00:31:58,740 at the colours of light coming down here, 635 00:31:58,740 --> 00:32:00,940 if we split them up using a spectroscope, 636 00:32:00,940 --> 00:32:03,620 we would see they have slightly different colours. 637 00:32:03,620 --> 00:32:06,420 The exact frequencies of light coming out 638 00:32:06,420 --> 00:32:08,220 are unique to these elements. 639 00:32:08,220 --> 00:32:10,700 Now these two elements, caesium and rubidium, 640 00:32:10,700 --> 00:32:14,380 were also first discovered in water. 641 00:32:14,380 --> 00:32:17,500 And they were discovered by Robert Bunsen. 642 00:32:17,500 --> 00:32:21,060 This is Bunsen of Bunsen burner fame, of course - 643 00:32:21,060 --> 00:32:22,580 not to be confused with 644 00:32:22,580 --> 00:32:25,740 Bunsen Honeydew from the Muppets, shown here! 645 00:32:25,740 --> 00:32:27,580 LAUGHTER 646 00:32:27,580 --> 00:32:31,860 But Robert Bunsen took litres of mineral water, evaporated this, 647 00:32:31,860 --> 00:32:36,860 and he found these new elements in the water using spectroscopy. 648 00:32:36,860 --> 00:32:38,740 And, in fact, he named these elements 649 00:32:38,740 --> 00:32:40,980 from the appearance of their spectra - 650 00:32:40,980 --> 00:32:43,820 caesium from the sky blue lines in its spectra, 651 00:32:43,820 --> 00:32:48,300 and rubidium from two very distinct red lines in its spectrum. 652 00:32:48,300 --> 00:32:51,100 OK, so, how do we find these elements, though? 653 00:32:51,100 --> 00:32:54,580 They appear in compounds in water, not as their elements. 654 00:32:54,580 --> 00:32:56,980 All of you, all you group 1 elements, 655 00:32:56,980 --> 00:32:58,860 you're actually metals. 656 00:32:58,860 --> 00:33:01,300 We certainly don't find metals in water. 657 00:33:01,300 --> 00:33:04,940 And that's because all of these metals actually react with water. 658 00:33:04,940 --> 00:33:07,180 And this is what we're going to show you now. 659 00:33:07,180 --> 00:33:09,140 So we have here a tank, 660 00:33:09,140 --> 00:33:13,260 and I'm going to add a tiny little piece of sodium to the tank. 661 00:33:13,260 --> 00:33:15,500 Let's have this one. A little piece of sodium. 662 00:33:15,500 --> 00:33:18,380 A little tiny piece. I'm going to drop it into the water. 663 00:33:18,380 --> 00:33:20,420 There it is, dancing around the surface. 664 00:33:20,420 --> 00:33:23,220 So it's lighter than water, floating on the top, 665 00:33:23,220 --> 00:33:25,540 but it's actually reacting with the water. 666 00:33:25,540 --> 00:33:27,380 We can see it's reacted there. 667 00:33:27,380 --> 00:33:28,980 It's giving out hydrogen gas. 668 00:33:28,980 --> 00:33:32,180 The sodium is giving up its electron to the water, 669 00:33:32,180 --> 00:33:35,700 to the hydrogen in the water, forming hydrogen gas, OK? 670 00:33:35,700 --> 00:33:38,380 It's rather disappointing to see that one, though. 671 00:33:38,380 --> 00:33:39,900 There's not a lot there. 672 00:33:39,900 --> 00:33:45,100 I think we need, actually, a bigger tank, and a bigger piece of sodium. 673 00:33:45,100 --> 00:33:46,540 So let's try this. 674 00:33:48,420 --> 00:33:51,420 OK, this is certainly a bigger piece of sodium. 675 00:33:51,420 --> 00:33:54,500 Now, of course, when this reaction is done at school, 676 00:33:54,500 --> 00:33:56,620 the teacher is always instructed 677 00:33:56,620 --> 00:33:59,300 to not use a piece larger than the size of a pea. 678 00:33:59,300 --> 00:34:01,620 And, well, I thought I'd show you why. 679 00:34:01,620 --> 00:34:05,060 So we've got a piece that IS a bit larger than the size of a pea. 680 00:34:05,060 --> 00:34:09,020 Now then, we're going to add this piece of sodium, then, to the water. 681 00:34:09,020 --> 00:34:11,140 Are you ready? And, step back. 682 00:34:13,220 --> 00:34:15,620 So it's floating on the surface there... 683 00:34:15,620 --> 00:34:18,260 EXPLOSION AUDIENCE GASPS 684 00:34:18,260 --> 00:34:21,820 HE LAUGHS There's certainly quite a lot of smoke! 685 00:34:21,820 --> 00:34:24,940 APPLAUSE AND CHEERING 686 00:34:33,660 --> 00:34:35,740 Well, you can certainly see why 687 00:34:35,740 --> 00:34:38,500 you shouldn't add a piece larger than the size of a pea! 688 00:34:38,500 --> 00:34:41,140 LAUGHTER COUGHING 689 00:34:41,140 --> 00:34:43,980 Oh, dear! I've poisoned the audience! 690 00:34:43,980 --> 00:34:47,340 It's chemistry! COUGHING 691 00:34:47,340 --> 00:34:48,540 Right, now... 692 00:34:48,540 --> 00:34:53,180 But it's not just water that sodium can give its electron to. 693 00:34:53,180 --> 00:34:59,900 We can also... It can give its electron to oxygen. 694 00:34:59,900 --> 00:35:01,700 So here is a piece of sodium 695 00:35:01,700 --> 00:35:03,940 and I'm just going to cut this now 696 00:35:03,940 --> 00:35:07,420 and chop it right down the middle. 697 00:35:07,420 --> 00:35:08,820 There we are. 698 00:35:10,300 --> 00:35:12,740 So this is beautiful, silvery metal. 699 00:35:12,740 --> 00:35:15,540 So this is what sodium normally looks like. 700 00:35:15,540 --> 00:35:18,500 But just as it's left here, exposed to the air, 701 00:35:18,500 --> 00:35:21,260 it's reacting with the oxygen in the air. 702 00:35:21,260 --> 00:35:24,460 It's actually giving up its electron to oxygen. 703 00:35:24,460 --> 00:35:26,540 OK, we can see it's changing. 704 00:35:26,540 --> 00:35:28,820 It's actually got a sort of white crust 705 00:35:28,820 --> 00:35:30,780 developing over the surface. 706 00:35:30,780 --> 00:35:32,500 But, actually, if we just have 707 00:35:32,500 --> 00:35:34,660 our periodic table up for the moment, 708 00:35:34,660 --> 00:35:37,020 and I want to focus on group 1 again. 709 00:35:37,020 --> 00:35:39,340 So others, down. Just group 1 up. 710 00:35:39,340 --> 00:35:41,180 So we have sodium here, 711 00:35:41,180 --> 00:35:44,260 and the key thing here is this outermost electron sodium has. 712 00:35:44,260 --> 00:35:46,260 I think we have a graphic to show this. 713 00:35:46,260 --> 00:35:48,260 This is the atomic structure of sodium. 714 00:35:48,260 --> 00:35:50,500 We have one outermost electron there. 715 00:35:50,500 --> 00:35:53,900 This is the thing that's very easily given in chemical reactions. 716 00:35:53,900 --> 00:35:55,580 But as we come down the group, 717 00:35:55,580 --> 00:35:58,020 you've all got this one outermost electron, 718 00:35:58,020 --> 00:36:00,660 but if we look at, say, caesium, right at the bottom, 719 00:36:00,660 --> 00:36:03,300 so here's caesium, and has lots more electrons, 720 00:36:03,300 --> 00:36:05,940 but, again, there's one outermost electron, 721 00:36:05,940 --> 00:36:09,580 and this is even more easily lost than it is for sodium. 722 00:36:09,580 --> 00:36:12,020 And, well, we have some here. 723 00:36:12,020 --> 00:36:15,300 This is caesium in this vessel. 724 00:36:15,300 --> 00:36:18,580 The problem was, we need to store it under argon, 725 00:36:18,580 --> 00:36:20,580 and we had a slight problem. 726 00:36:20,580 --> 00:36:23,580 We sealed it up so well, we can't get it out! 727 00:36:23,580 --> 00:36:25,420 LAUGHTER 728 00:36:25,420 --> 00:36:27,780 So, I think the simplest thing to do 729 00:36:27,780 --> 00:36:29,980 is actually to hit it with a hammer, 730 00:36:29,980 --> 00:36:31,940 which is what I'm going to do. 731 00:36:31,940 --> 00:36:34,180 HAMMERING Oh, well, that did it! 732 00:36:34,180 --> 00:36:36,140 This is such a reactive element 733 00:36:36,140 --> 00:36:39,340 that is soon as it comes into contact with the air... 734 00:36:39,340 --> 00:36:41,540 in fact, if you have the lights down, 735 00:36:41,540 --> 00:36:44,940 you might be able to see some of the sparks that are... 736 00:36:44,940 --> 00:36:46,180 ooh, yes, look at this. 737 00:36:46,180 --> 00:36:48,100 This is SO reactive that as soon as... 738 00:36:48,100 --> 00:36:49,500 Ooh, dear! Lots of sparks! 739 00:36:49,500 --> 00:36:52,860 ..as soon as it as it comes into contact with the air, it's gone off. 740 00:36:52,860 --> 00:36:56,100 It WAS a nice, shiny metal. It was a sort of silvery colour. 741 00:36:56,100 --> 00:36:58,220 Sometimes it has a slight golden colour, 742 00:36:58,220 --> 00:37:01,580 but when comes into contact with air, it forms this black oxide. 743 00:37:01,580 --> 00:37:04,140 So, the caesium is incredibly reactive 744 00:37:04,140 --> 00:37:07,260 and it's given its electron to the oxygen. 745 00:37:07,260 --> 00:37:10,820 But there are other things that can take the electron away 746 00:37:10,820 --> 00:37:12,980 from these group 1 elements, 747 00:37:12,980 --> 00:37:16,140 and one of them is contained in this, in bleach. 748 00:37:16,140 --> 00:37:18,660 Does anyone know what element is in this? 749 00:37:18,660 --> 00:37:20,380 AUDIENCE MEMBER: Chlorine! 750 00:37:20,380 --> 00:37:22,340 Chlorine! Where's chlorine? 751 00:37:22,340 --> 00:37:25,260 Yes, you're in bleach. This gives the bleach its colour. 752 00:37:25,260 --> 00:37:28,140 You're a really poisonous, nasty element, I'm afraid. 753 00:37:28,140 --> 00:37:31,780 You were used in World War I as a toxic gas. 754 00:37:31,780 --> 00:37:33,340 Not very nice! 755 00:37:33,340 --> 00:37:36,940 But you're very efficient, though, at taking electrons from things. 756 00:37:36,940 --> 00:37:39,580 OK, we're going to see some chlorine in just a moment, 757 00:37:39,580 --> 00:37:42,620 but before I show you that, I want to show you something else. 758 00:37:42,620 --> 00:37:45,260 This is a really, really remarkable book. 759 00:37:45,260 --> 00:37:48,820 This is from the archives in the Royal Institution here. 760 00:37:48,820 --> 00:37:51,860 And this was from a lecture 761 00:37:51,860 --> 00:37:55,180 that was delivered exactly 200 years ago, in 1812. 762 00:37:55,180 --> 00:37:57,740 And the lectures were four lectures, 763 00:37:57,740 --> 00:38:01,540 being part of a course on the elements of chemical philosophy, 764 00:38:01,540 --> 00:38:05,060 delivered by Sir Humphrey Davy exactly 200 years ago. 765 00:38:05,060 --> 00:38:08,020 Sir Humphrey Davy was the first person to isolate, 766 00:38:08,020 --> 00:38:10,860 among other elements, sodium and potassium, 767 00:38:10,860 --> 00:38:13,100 and he also named chlorine over there. 768 00:38:13,100 --> 00:38:16,540 And these lectures were written down during the lecture course 769 00:38:16,540 --> 00:38:18,780 by a young Michael Faraday, 770 00:38:18,780 --> 00:38:21,940 who was sitting in the audience, exactly where you are now. 771 00:38:21,940 --> 00:38:24,660 Davy was so impressed with these notes 772 00:38:24,660 --> 00:38:26,860 that Faraday wrote up of the lectures, 773 00:38:26,860 --> 00:38:28,340 that he gave him a job. 774 00:38:28,340 --> 00:38:30,940 He got a job here at the Royal Institution 775 00:38:30,940 --> 00:38:34,140 and became one of the world's most famous scientists ever. 776 00:38:34,140 --> 00:38:36,260 Now, I'm certainly no Humphrey Davy, 777 00:38:36,260 --> 00:38:38,580 but who knows, sitting in this audience 778 00:38:38,580 --> 00:38:41,540 there may well be the next Michael Faraday. 779 00:38:41,540 --> 00:38:43,980 Now, this is what I wanted to show you, though. 780 00:38:43,980 --> 00:38:47,620 In this book, Experiments Belonging To The Lecture On Chlorine, 781 00:38:47,620 --> 00:38:51,900 it says, "Mr Davy exhibited a specimen of chlorine gas. 782 00:38:51,900 --> 00:38:54,180 "It was in a clean glass tube." 783 00:38:54,180 --> 00:39:00,380 OK, now, we actually have that original sample of chlorine gas. 784 00:39:00,380 --> 00:39:05,260 Here it is. This is the one that Davy exhibited back in 1812, 785 00:39:05,260 --> 00:39:07,260 which is quite remarkable. 786 00:39:07,260 --> 00:39:10,380 So chlorine gets its name, Davy gave it its name, 787 00:39:10,380 --> 00:39:12,940 from the Greek, "chloros" meaning "green", 788 00:39:12,940 --> 00:39:15,460 because of this greeny colour that it has. 789 00:39:15,460 --> 00:39:18,900 We even have a sample of the original sodium, 790 00:39:18,900 --> 00:39:22,780 and this is Davy's original sodium, 791 00:39:22,780 --> 00:39:25,100 prepared here at the Royal Institution. 792 00:39:25,100 --> 00:39:27,940 This is the metal, floating, protected in oil, 793 00:39:27,940 --> 00:39:31,980 because, as we've seen, it goes off in air very quickly. 794 00:39:31,980 --> 00:39:34,940 So, we've got sodium and we've got chlorine. 795 00:39:34,940 --> 00:39:37,580 Well, what happens when you mix the two? 796 00:39:37,580 --> 00:39:39,460 Well, you get some sodium chloride. 797 00:39:39,460 --> 00:39:42,460 Now, they would kill me if I did this, of course, with these, 798 00:39:42,460 --> 00:39:46,340 so I'm not going to use the original samples of sodium and chlorine. 799 00:39:46,340 --> 00:39:49,340 But we do have some other samples here. 800 00:39:49,340 --> 00:39:52,180 Here's our sodium, here's our chlorine. 801 00:39:52,180 --> 00:39:56,220 And you can see this beautiful green colour now of the chlorine, 802 00:39:56,220 --> 00:39:59,700 you can see the beautiful silvery colour of the sodium. 803 00:39:59,700 --> 00:40:01,780 We've taken all the air out of this side, 804 00:40:01,780 --> 00:40:05,020 because we know that sodium reacts very violently with air, 805 00:40:05,020 --> 00:40:06,620 so there's no air here. 806 00:40:06,620 --> 00:40:09,900 I'm just going to pop my goggles on, if I can do that one-handedly. 807 00:40:09,900 --> 00:40:14,140 There we go. And I'm now going to let the chlorine from this side 808 00:40:14,140 --> 00:40:16,380 into this side, and see what happens. 809 00:40:16,380 --> 00:40:18,020 So let's have a look. 810 00:40:18,020 --> 00:40:21,260 Look at that. This is sodium meets chlorine, 811 00:40:21,260 --> 00:40:24,180 and the silver mirror has disappeared, 812 00:40:24,180 --> 00:40:28,580 and we've got this white crust forming all the way round here. 813 00:40:28,580 --> 00:40:32,420 It's gone white, looks like salt, and, well, 814 00:40:32,420 --> 00:40:34,660 that's because what we've made here is salt - 815 00:40:34,660 --> 00:40:36,700 it's sodium chloride. 816 00:40:36,700 --> 00:40:39,300 So the chlorine reacts with the sodium, 817 00:40:39,300 --> 00:40:42,380 the chlorine takes the electron from the sodium, 818 00:40:42,380 --> 00:40:44,020 to form white sodium chloride. 819 00:40:44,020 --> 00:40:46,860 This is just the sort of thing you would put on your chips. 820 00:40:46,860 --> 00:40:48,780 The chlorine itself is poisonous. 821 00:40:48,780 --> 00:40:52,140 It reacts by taking electrons from your body and poisons you. 822 00:40:52,140 --> 00:40:54,780 The sodium is poisonous. It gives its electron to you. 823 00:40:54,780 --> 00:40:56,620 But once they've reacted, 824 00:40:56,620 --> 00:40:59,380 we've got sodium chloride and you eat it. 825 00:40:59,380 --> 00:41:01,180 OK, thank you very much. 826 00:41:01,180 --> 00:41:04,300 APPLAUSE 827 00:41:09,820 --> 00:41:12,460 But there are actually different sorts of salt. 828 00:41:12,460 --> 00:41:15,700 Sodium chloride is just one salt. There are others. 829 00:41:15,700 --> 00:41:18,740 And if we have our halogens up for a moment... 830 00:41:18,740 --> 00:41:21,420 OK, all of you are very good at forming salts, 831 00:41:21,420 --> 00:41:24,420 especially with group 1. Can we have group 1 up, as well, please? 832 00:41:24,420 --> 00:41:26,580 OK, any mixtures of you would form salts. 833 00:41:26,580 --> 00:41:28,700 Not only could we have sodium chloride, 834 00:41:28,700 --> 00:41:31,820 we could have potassium bromide, potassium chloride, or so on. 835 00:41:31,820 --> 00:41:34,100 In fact, all of you halogens... 836 00:41:34,100 --> 00:41:37,940 Do you know what the name "halogen" actually means? Does anyone know? 837 00:41:37,940 --> 00:41:40,260 Does anyone know anywhere? 838 00:41:40,260 --> 00:41:43,220 It means "salt-former". 839 00:41:43,220 --> 00:41:45,940 So you're all really good forming salts. 840 00:41:45,940 --> 00:41:49,180 In fact, that's how, as a group, you get your name. 841 00:41:49,180 --> 00:41:51,780 So salts, though, have very different properties 842 00:41:51,780 --> 00:41:53,700 when they're dissolved in the water. 843 00:41:53,700 --> 00:41:56,140 The water itself is completely different. 844 00:41:56,140 --> 00:41:58,180 Seawater is not the same as normal water, 845 00:41:58,180 --> 00:42:00,860 and, well, we have some seawater here to show you. 846 00:42:00,860 --> 00:42:05,020 Thank you very much, periodic tables. If you go down for a moment. 847 00:42:05,020 --> 00:42:07,300 So I was fortunate enough to visit the Dead Sea. 848 00:42:07,300 --> 00:42:10,340 In fact, this is me floating in the Dead Sea up here. 849 00:42:10,340 --> 00:42:12,380 LAUGHTER So while I was floating, 850 00:42:12,380 --> 00:42:15,340 I was thinking, "Well, what would it be like? 851 00:42:15,340 --> 00:42:19,460 "What sort of things could we get to float on the Dead Sea?" 852 00:42:19,460 --> 00:42:22,700 Well, I need a volunteer, actually, to help out with this. 853 00:42:22,700 --> 00:42:24,660 And we'll have somebody from... 854 00:42:24,660 --> 00:42:27,140 Yes, yes. If you'd like to come down. Lovely. 855 00:42:27,140 --> 00:42:29,420 APPLAUSE Thank you very much. 856 00:42:29,420 --> 00:42:31,540 If you'd like to face the front here. 857 00:42:31,540 --> 00:42:33,580 What's your name, please? Katie. 858 00:42:33,580 --> 00:42:36,740 Right, good. We need to put some protective clothing when you, 859 00:42:36,740 --> 00:42:39,700 so just come over here and put on some protective clothing. 860 00:42:39,700 --> 00:42:42,420 I've got a block of metal here. 861 00:42:42,420 --> 00:42:44,820 Now, what do you think to this block of metal? 862 00:42:44,820 --> 00:42:47,300 If you just hold this. What do you think? 863 00:42:47,300 --> 00:42:49,940 It's really heavy. It's really heavy, yes? 864 00:42:49,940 --> 00:42:53,100 OK, really heavy. What do you think? How heavy? 865 00:42:53,100 --> 00:42:54,420 Quite heavy, yeah. 866 00:42:54,420 --> 00:42:56,660 So this IS solid metal. This is actually... 867 00:42:56,660 --> 00:42:59,100 You're looking very good in those! Very fetching! 868 00:42:59,100 --> 00:43:01,740 We've got a step here, which was a very good thing! 869 00:43:01,740 --> 00:43:03,740 If you'd like to stand on this step. 870 00:43:03,740 --> 00:43:07,420 OK, this is some salty water. This is essentially seawater. 871 00:43:07,420 --> 00:43:09,460 I'm going to put on my gloves, as well. 872 00:43:09,460 --> 00:43:11,980 You haven't held this yet. If you just hold that. 873 00:43:11,980 --> 00:43:13,620 Just stand there for a moment. 874 00:43:13,620 --> 00:43:16,100 Right, what you think of that? Quite heavy? 875 00:43:16,100 --> 00:43:17,940 Yeah! Quite heavy, actually! 876 00:43:17,940 --> 00:43:19,420 Yes, it is quite heavy. 877 00:43:19,420 --> 00:43:22,620 Right, do you think it's going to float in the Dead Sea, 878 00:43:22,620 --> 00:43:24,060 or sink in the Dead Sea? 879 00:43:26,060 --> 00:43:27,540 What you think? 50-50. 880 00:43:27,540 --> 00:43:30,180 Float or sink? Ask the audience? Float. 881 00:43:30,180 --> 00:43:32,980 Ah, float, OK. Float in the Dead Sea. Maybe. It's quite heavy. 882 00:43:32,980 --> 00:43:34,420 Covering your bets there. 883 00:43:34,420 --> 00:43:36,500 OK, it is quite heavy, though, isn't it? 884 00:43:36,500 --> 00:43:38,860 Let's see, shall we? We're going to drop it in. 885 00:43:38,860 --> 00:43:40,500 You take that side. That's it. 886 00:43:40,500 --> 00:43:41,940 And you put that in the water. 887 00:43:41,940 --> 00:43:45,220 Lower it in gently, you don't want to splash it everywhere. 888 00:43:45,220 --> 00:43:47,980 That's it. OK, very good. And just let go. 889 00:43:47,980 --> 00:43:50,060 And... Oh, no! 890 00:43:50,060 --> 00:43:51,500 Aw! Well, it sinks. 891 00:43:51,500 --> 00:43:54,500 It did sink, yes! It sank pretty quickly. 892 00:43:54,500 --> 00:43:56,260 It was quite heavy, wasn't it? 893 00:43:56,260 --> 00:43:58,060 It did sink pretty quickly there. 894 00:43:58,060 --> 00:44:00,060 I'll see if I can fish it out for you. 895 00:44:00,060 --> 00:44:02,060 I'll do this, I've got longer gloves. 896 00:44:02,060 --> 00:44:04,500 And...ooh, not that long! LAUGHTER 897 00:44:04,500 --> 00:44:08,100 Anyway, right, out comes the magnesium here. 898 00:44:08,100 --> 00:44:09,820 This is a block of pure magnesium. 899 00:44:09,820 --> 00:44:12,220 It is actually quite heavy, you're right! 900 00:44:12,220 --> 00:44:15,140 OK, there we are. Now, we've got some other water here. 901 00:44:15,140 --> 00:44:17,260 So this one contains sodium salts, 902 00:44:17,260 --> 00:44:19,540 but this one contains caesium salts. 903 00:44:19,540 --> 00:44:22,140 And if we just have our group 1 up again for a moment. 904 00:44:22,140 --> 00:44:23,780 Oh, very good! Very efficient! 905 00:44:23,780 --> 00:44:25,460 Sodium right at the top there, 906 00:44:25,460 --> 00:44:27,460 and as we go down, we get to caesium. 907 00:44:27,460 --> 00:44:30,500 And, so, caesium is actually heavier than sodium. 908 00:44:30,500 --> 00:44:34,060 And, now, how quickly do you think this is going to sink in this one? 909 00:44:34,060 --> 00:44:36,780 Er, maybe a bit longer. Take a bit longer to sink? 910 00:44:36,780 --> 00:44:39,020 Yep, OK, all right. So shall we try this one? 911 00:44:39,020 --> 00:44:40,940 I'm just going to put this in the water. 912 00:44:40,940 --> 00:44:43,420 Are you ready? Do you want to hold it there, as well? 913 00:44:43,420 --> 00:44:45,740 Just gently let go. And, ready? 914 00:44:45,740 --> 00:44:47,380 After three. 1, 2, 3, go! 915 00:44:49,580 --> 00:44:51,820 AUDIENCE GASPS 916 00:44:51,820 --> 00:44:53,500 Ooh! 917 00:44:53,500 --> 00:44:56,180 LAUGHTER 918 00:44:56,180 --> 00:44:59,540 Watch out for your gloves! LAUGHTER 919 00:44:59,540 --> 00:45:01,580 No, so it's not actually going to sink. 920 00:45:01,580 --> 00:45:04,820 It actually floats in the water. So I'll just fish that out, 921 00:45:04,820 --> 00:45:06,980 and I think you should get a big round of applause 922 00:45:06,980 --> 00:45:09,380 for your help there. APPLAUSE 923 00:45:09,380 --> 00:45:10,500 Thank you. 924 00:45:10,500 --> 00:45:13,300 We'll just take those off you. That's it. Lovely stuff. 925 00:45:13,300 --> 00:45:15,380 Thank you very much indeed. 926 00:45:15,380 --> 00:45:18,860 Yes, the block of metal actually floats in the caesium salts, 927 00:45:18,860 --> 00:45:23,540 and that's because caesium itself is a heavier atom than sodium is. 928 00:45:23,540 --> 00:45:26,980 We can get other salts, though, from the Dead Sea, for instance. 929 00:45:26,980 --> 00:45:29,980 It's not just sodium chloride. In fact, in the Dead Sea 930 00:45:29,980 --> 00:45:32,020 it's quite rich in another salt. 931 00:45:32,020 --> 00:45:34,140 If we have our halogens back, please. 932 00:45:34,140 --> 00:45:36,900 OK, we have bromine in the Dead Sea, as well. 933 00:45:36,900 --> 00:45:40,180 It's not as bromine itself, not as the element. It's as bromide. 934 00:45:40,180 --> 00:45:42,700 This is where it's taken an electron from something 935 00:45:42,700 --> 00:45:44,500 and formed a negative bromide ion. 936 00:45:44,500 --> 00:45:47,420 So we'd get things like potassium bromide, sodium bromide, 937 00:45:47,420 --> 00:45:49,540 if we evaporated our Dead Sea water. 938 00:45:49,540 --> 00:45:52,340 And, actually, I can demonstrate this 939 00:45:52,340 --> 00:45:54,500 with some of the Dead Sea water. 940 00:45:54,500 --> 00:45:56,940 I've got some concentrated Dead Sea water. 941 00:45:56,940 --> 00:45:58,900 I brought this back from the Dead Sea. 942 00:45:58,900 --> 00:46:01,860 Just the sort of thing you normally bring back, I suppose, 943 00:46:01,860 --> 00:46:03,100 if you're a chemist! 944 00:46:03,100 --> 00:46:05,500 Right, here we are. Here's my Dead Sea water. 945 00:46:05,500 --> 00:46:09,660 And I'm just going to add some bleach to that. 946 00:46:09,660 --> 00:46:12,260 Of course, the bleach has chlorine atoms in it. 947 00:46:12,260 --> 00:46:14,460 Watch what happens, just give it a bit of a... 948 00:46:14,460 --> 00:46:17,540 AUDIENCE GASPS 949 00:46:17,540 --> 00:46:19,980 OK. This, the colour that you now see... 950 00:46:19,980 --> 00:46:21,740 And we haven't cheated in any way, 951 00:46:21,740 --> 00:46:24,660 this really is just Dead Sea water that I brought back. 952 00:46:24,660 --> 00:46:27,060 We just concentrated it a bit by removing some water. 953 00:46:27,060 --> 00:46:28,500 This is just bleach. 954 00:46:28,500 --> 00:46:30,940 The colour that you see now is bromine. 955 00:46:30,940 --> 00:46:33,980 So with our halogens, we've got bromide here, 956 00:46:33,980 --> 00:46:37,140 and I've just added some chlorine that was in the bleach. 957 00:46:37,140 --> 00:46:40,540 So what we have there, the bromide reacts with the chlorine, 958 00:46:40,540 --> 00:46:43,340 chlorine takes the electron from bromide, 959 00:46:43,340 --> 00:46:46,700 and forums bromine element and leaves chloride ions. 960 00:46:46,700 --> 00:46:49,620 But chlorine, look behind you. Who's behind you? 961 00:46:49,620 --> 00:46:51,020 Fluorine! 962 00:46:51,020 --> 00:46:52,660 Fluorine, exactly! 963 00:46:52,660 --> 00:46:56,100 No fluorine is even better at taking electrons away, 964 00:46:56,100 --> 00:46:59,140 and fluorine can take the electron away from chloride. 965 00:46:59,140 --> 00:47:00,620 OK, fluorine, in fact... 966 00:47:00,620 --> 00:47:02,820 That's right, give us a little wave! 967 00:47:02,820 --> 00:47:05,420 Fluorine, you are THE most reactive non-metal 968 00:47:05,420 --> 00:47:07,140 in the entire periodic table. 969 00:47:07,140 --> 00:47:09,980 You will steal an electron from every other element 970 00:47:09,980 --> 00:47:13,140 in the entire periodic table, with the slight exception 971 00:47:13,140 --> 00:47:15,620 of the very inert noble gases sitting next to you. 972 00:47:15,620 --> 00:47:18,860 But everything else, you will react with. Very, very violent. 973 00:47:18,860 --> 00:47:21,300 Fluorine is probably THE most reactive element 974 00:47:21,300 --> 00:47:22,940 in the entire periodic table. 975 00:47:22,940 --> 00:47:25,180 Certainly the most reactive non-metal. 976 00:47:25,180 --> 00:47:28,820 Even as a chemist, I had never seen any fluorine, 977 00:47:28,820 --> 00:47:31,260 and I thought, for these lectures, 978 00:47:31,260 --> 00:47:35,500 it would be really nice to bring some fluorine into the lectures 979 00:47:35,500 --> 00:47:37,780 and I needed to find a specialist to do this. 980 00:47:37,780 --> 00:47:41,100 So, would you please welcome, from the University of Leicester, 981 00:47:41,100 --> 00:47:43,460 Professor Eric Hope, a fluorine chemist. 982 00:47:43,460 --> 00:47:46,220 APPLAUSE 983 00:47:47,740 --> 00:47:49,500 Eric, thank you for coming along. 984 00:47:49,500 --> 00:47:51,380 So, Eric is a fluorine specialist. 985 00:47:51,380 --> 00:47:53,420 Fluorine is incredibly reactive. 986 00:47:53,420 --> 00:47:56,380 It reacts with just about everything, doesn't it? Indeed. 987 00:47:56,380 --> 00:47:59,420 So, the question everyone wants to ask is, how do you store it? 988 00:47:59,420 --> 00:48:02,180 Doesn't it react with the container you put it in? 989 00:48:02,180 --> 00:48:03,700 It does react with the container. 990 00:48:03,700 --> 00:48:06,580 You can store it in metal containers, stainless steel, 991 00:48:06,580 --> 00:48:08,900 or we hold it in nickel containers in Leicester. 992 00:48:08,900 --> 00:48:11,180 And what happens is the fluorine reacts 993 00:48:11,180 --> 00:48:12,900 with a coating of the metal, 994 00:48:12,900 --> 00:48:15,700 you get nickel difluoride, a very few microns thick, 995 00:48:15,700 --> 00:48:17,780 protects the rest of the nickel metal, 996 00:48:17,780 --> 00:48:19,740 and you get an impervious layer. 997 00:48:19,740 --> 00:48:23,140 So it HAS reacted, and what it's formed is pretty inert afterwards. 998 00:48:23,140 --> 00:48:24,340 Indeed, yes. 999 00:48:24,340 --> 00:48:27,420 But fluorine is incredibly reactive and dangerous, isn't it? 1000 00:48:27,420 --> 00:48:30,660 If you control and handle it under appropriate conditions, 1001 00:48:30,660 --> 00:48:33,700 then it is dangerous, but it's not THAT dangerous. 1002 00:48:33,700 --> 00:48:36,660 It's very reactive, isn't it? It'll react, as you said, 1003 00:48:36,660 --> 00:48:39,340 with virtually every element in the periodic table. 1004 00:48:39,340 --> 00:48:42,980 When I contacted Eric, I thought, fluorine, really reactive, 1005 00:48:42,980 --> 00:48:46,300 it would be very great if we could bring some of this into the RI. 1006 00:48:46,300 --> 00:48:49,060 But one reaction that I've always wanted to try 1007 00:48:49,060 --> 00:48:51,140 is the reaction between fluorine - 1008 00:48:51,140 --> 00:48:54,420 because, you know, it is one of THE most reactive non-metals - 1009 00:48:54,420 --> 00:48:56,940 I thought I'd like to try the reaction of fluorine 1010 00:48:56,940 --> 00:48:59,980 with THE most reactive metal in the periodic table, caesium. 1011 00:48:59,980 --> 00:49:02,780 Yes, you are best electron-giver! Very generous! 1012 00:49:02,780 --> 00:49:05,260 So this should be a really violent reaction. 1013 00:49:05,260 --> 00:49:06,940 I thought, I'd love to see this! 1014 00:49:06,940 --> 00:49:09,820 What did you think of this, when I said I wanted to try 1015 00:49:09,820 --> 00:49:12,260 the reaction of fluorine with caesium? 1016 00:49:12,260 --> 00:49:15,460 I thought it was the most outlandish thing I'd ever heard, 1017 00:49:15,460 --> 00:49:18,540 and it took me a good 24 hours to think about whether or not 1018 00:49:18,540 --> 00:49:20,660 it was feasible or possible to actually do. 1019 00:49:20,660 --> 00:49:23,820 OK. Yes, exactly, we did wonder whether we could actually do this. 1020 00:49:23,820 --> 00:49:25,980 Shall we just have the periodic table down? 1021 00:49:25,980 --> 00:49:28,060 We thought, "How could we do this safely?" 1022 00:49:28,060 --> 00:49:29,620 And we did have a practice 1023 00:49:29,620 --> 00:49:31,780 just to make sure we could do this safely. 1024 00:49:31,780 --> 00:49:33,900 In fact, the remarkable thing was, 1025 00:49:33,900 --> 00:49:37,020 as I say, I'm a chemist, and I've never actually seen... 1026 00:49:37,020 --> 00:49:39,660 I hadn't seen fluorine before, before I went up to Leicester, 1027 00:49:39,660 --> 00:49:42,260 and remarkably, well... I've never seen caesium before! 1028 00:49:42,260 --> 00:49:44,060 Eric had never seen caesium! 1029 00:49:44,060 --> 00:49:46,980 So we thought we HAD to get together, really! 1030 00:49:46,980 --> 00:49:49,780 So I thought I'd bring my caesium along to Leicester, 1031 00:49:49,780 --> 00:49:51,340 and we did test things, 1032 00:49:51,340 --> 00:49:53,700 and we're going to try and do this for you now. 1033 00:49:53,700 --> 00:49:56,700 I'm actually just going to hold this in my hand. 1034 00:49:56,700 --> 00:50:00,100 Just holding this in my hand actually just melts the caesium. 1035 00:50:00,100 --> 00:50:03,860 So the bond between the caesium atoms here are so weak, 1036 00:50:03,860 --> 00:50:06,940 just holding it in my hand melts this. There we are. 1037 00:50:06,940 --> 00:50:09,780 We've certainly got some caesium at the bottom of this tube. 1038 00:50:11,620 --> 00:50:13,540 Right, we're going to try, then, 1039 00:50:13,540 --> 00:50:16,420 the reaction between caesium and fluorine. 1040 00:50:16,420 --> 00:50:21,860 The caesium is protected by this blanket of argon... 1041 00:50:24,700 --> 00:50:27,180 ..which is heavier than air. 1042 00:50:27,180 --> 00:50:29,980 And we've seen that caesium reacts with the air. 1043 00:50:33,100 --> 00:50:36,060 And I'm just going to lower this on... 1044 00:50:41,780 --> 00:50:44,500 ..like so, and push this down. 1045 00:50:47,020 --> 00:50:49,100 OK, and I think we're ready to try, then. 1046 00:50:51,060 --> 00:50:52,380 Ah! 1047 00:50:52,380 --> 00:50:55,380 AUDIENCE GASPS APPLAUSE 1048 00:51:18,380 --> 00:51:19,780 We have to just use a tiny, tiny bit. It's in this tube here. 1049 00:51:19,780 --> 00:51:23,020 But it did react very, very violently with the caesium, 1050 00:51:23,020 --> 00:51:24,660 to form caesium fluoride. 1051 00:51:24,660 --> 00:51:27,460 OK, well, I think we need to give a big round of applause 1052 00:51:27,460 --> 00:51:29,300 to Professor Eric Hope. 1053 00:51:29,300 --> 00:51:31,220 APPLAUSE 1054 00:51:34,420 --> 00:51:37,860 So, once the caesium has reacted with the fluorine, 1055 00:51:37,860 --> 00:51:40,500 again, the caesium gives up its electron, 1056 00:51:40,500 --> 00:51:43,980 and it's no longer the reactive caesium metal that we started with. 1057 00:51:43,980 --> 00:51:46,820 And, of course, the fluorine, once it grabs the electron, 1058 00:51:46,820 --> 00:51:49,420 it's no longer the reactive fluorine we started with. 1059 00:51:49,420 --> 00:51:51,460 We've got fluoride ion. 1060 00:51:51,460 --> 00:51:54,500 And actually, remarkably, fluoride is something that, again, 1061 00:51:54,500 --> 00:51:57,380 you can find in every glass of drinking water you have. 1062 00:51:57,380 --> 00:52:00,100 This is actually added to our tap water 1063 00:52:00,100 --> 00:52:03,420 because it protects our teeth and prevents decay. 1064 00:52:03,420 --> 00:52:05,540 Now, talking of preventing decay, 1065 00:52:05,540 --> 00:52:09,140 I think we need to see how our Fountain of Youth volunteer got on, 1066 00:52:09,140 --> 00:52:12,380 and see how whether it really has worked after all. 1067 00:52:12,380 --> 00:52:14,860 So, Tim, how's it doing? 1068 00:52:14,860 --> 00:52:18,060 Has it worked? I feel a lot younger! 1069 00:52:18,060 --> 00:52:20,100 Tim, is that really you?! 1070 00:52:21,420 --> 00:52:24,300 Ah, I can see what they did there! 1071 00:52:24,300 --> 00:52:27,580 LAUGHTER AND APPLAUSE 1072 00:52:31,260 --> 00:52:33,500 Tim, do you feel any different at all? 1073 00:52:33,500 --> 00:52:35,940 No different at all, I'm afraid. Just the same age. 1074 00:52:35,940 --> 00:52:39,620 OK, so it really looks like our Fountain of Youth water 1075 00:52:39,620 --> 00:52:42,860 perhaps isn't restoring Tim's youth to him. 1076 00:52:42,860 --> 00:52:46,540 But, nonetheless, water does play a very important role in our lives. 1077 00:52:46,540 --> 00:52:48,340 Without it, we'd all be dead. 1078 00:52:48,340 --> 00:52:51,140 And this is because water actually enables 1079 00:52:51,140 --> 00:52:53,300 chemical reactions to take place, 1080 00:52:53,300 --> 00:52:56,820 both inside the cells in your body and in other reactions. 1081 00:52:56,820 --> 00:53:01,540 And this is what we're going to demonstrate now. I have... 1082 00:53:01,540 --> 00:53:06,740 We've placed some magnesium powder and some silver nitrate. 1083 00:53:06,740 --> 00:53:09,300 Now, they are touching each other at the moment. 1084 00:53:09,300 --> 00:53:12,740 They're mixed up very intimately, but not quite intimately enough. 1085 00:53:12,740 --> 00:53:15,500 What they need is to get into really close contact, 1086 00:53:15,500 --> 00:53:17,780 and we do that by adding a drop of water. 1087 00:53:17,780 --> 00:53:21,860 OK, now, they've given me a glass of water and a pipette, 1088 00:53:21,860 --> 00:53:25,940 but I think I'm going to need the slightly longer pipette, please. 1089 00:53:25,940 --> 00:53:27,380 This is quite a violent... 1090 00:53:27,380 --> 00:53:29,940 Thank you, that's a better one. Right, now... 1091 00:53:31,820 --> 00:53:34,060 I'm going to take the lid off of this. 1092 00:53:34,060 --> 00:53:36,500 It's sitting here quite happily the moment, 1093 00:53:36,500 --> 00:53:38,300 nothing is taking place, 1094 00:53:38,300 --> 00:53:41,660 until we add a drop of water. 1095 00:53:41,660 --> 00:53:43,860 OK, I'm adding it now. 1096 00:53:45,220 --> 00:53:47,820 AUDIENCE GASPS 1097 00:53:47,820 --> 00:53:50,740 APPLAUSE 1098 00:53:58,380 --> 00:54:02,180 So this is an incredibly violent reaction that takes place, 1099 00:54:02,180 --> 00:54:06,140 but it didn't take place until we added the water. 1100 00:54:06,140 --> 00:54:09,740 So, maybe this gives us a method for slowing reactions down, 1101 00:54:09,740 --> 00:54:11,620 if we remove the water. 1102 00:54:11,620 --> 00:54:14,700 Well, I think, actually, it's getting time for my dinner, 1103 00:54:14,700 --> 00:54:17,940 and they've brought on some bananas! 1104 00:54:17,940 --> 00:54:21,580 Great! And these bananas have seen better days. 1105 00:54:21,580 --> 00:54:26,780 Now, these bananas, I know, are two weeks old, actually. 1106 00:54:26,780 --> 00:54:28,220 They've been sort of...eurgh! 1107 00:54:30,100 --> 00:54:31,660 AUDIENCE GROANS 1108 00:54:31,660 --> 00:54:33,940 It's actually a banana... 1109 00:54:33,940 --> 00:54:36,540 AUDIENCE GROANS LOUDLY 1110 00:54:37,980 --> 00:54:41,420 It's seen better days, I think. 1111 00:54:41,420 --> 00:54:43,740 But this banana... 1112 00:54:43,740 --> 00:54:46,780 ..this banana, this one was two weeks old. 1113 00:54:46,780 --> 00:54:50,340 This banana here is actually six YEARS old. 1114 00:54:50,340 --> 00:54:53,260 AUDIENCE GROANS Yeah, if I was going to eat one, 1115 00:54:53,260 --> 00:54:55,220 I know which one I'd rather have! 1116 00:54:55,220 --> 00:54:57,140 Now, why has this one lasted so long? 1117 00:54:57,140 --> 00:54:59,180 Actually, what do you think? Have a look at this. 1118 00:54:59,180 --> 00:55:01,780 What do you think? What does it feel like? 1119 00:55:01,780 --> 00:55:03,140 Scaly. Scaly? Uh-huh. 1120 00:55:03,140 --> 00:55:06,660 What do you think? What do you think it feels like? 1121 00:55:06,660 --> 00:55:09,020 Quite hard. Quite hard, yes. 1122 00:55:09,020 --> 00:55:10,540 It IS quite hard. 1123 00:55:10,540 --> 00:55:13,940 And this is because we've removed all the water from this banana. 1124 00:55:13,940 --> 00:55:15,820 But this has actually preserved it. 1125 00:55:15,820 --> 00:55:18,060 It's stopped the reactions taking place, 1126 00:55:18,060 --> 00:55:20,100 the normal reactions where things go bad, 1127 00:55:20,100 --> 00:55:22,100 reactions taking place in the cells. 1128 00:55:22,100 --> 00:55:24,340 If we remove the water, they can't happen. 1129 00:55:24,340 --> 00:55:27,580 And, well, maybe this could be a way of preserving our good looks, 1130 00:55:27,580 --> 00:55:29,220 if we just remove the water? 1131 00:55:29,220 --> 00:55:31,820 Well, you could, and this is what you might look like. 1132 00:55:31,820 --> 00:55:34,900 LAUGHTER Well, this chap might not look too good, 1133 00:55:34,900 --> 00:55:39,500 but he is 800 years old, which is quite remarkable! 1134 00:55:39,500 --> 00:55:42,060 And the reason he's survived looking like this 1135 00:55:42,060 --> 00:55:45,060 is because all the water was removed when he died. 1136 00:55:45,060 --> 00:55:47,100 He died in the north coast of Peru. 1137 00:55:47,100 --> 00:55:49,780 It's very dry there, and removing the water 1138 00:55:49,780 --> 00:55:52,420 has actually preserved the cells of his body. 1139 00:55:52,420 --> 00:55:56,500 So maybe, then, this does give us a clue to eternal life - 1140 00:55:56,500 --> 00:55:59,140 Remove the water and you can live a long time - 1141 00:55:59,140 --> 00:56:00,740 well, looking like that - 1142 00:56:00,740 --> 00:56:04,780 but, of course, we need water for our reactions to take place, 1143 00:56:04,780 --> 00:56:08,020 and so, well, I certainly know which one I'm going to choose. 1144 00:56:08,020 --> 00:56:09,860 I think I'm going to stick to 1145 00:56:09,860 --> 00:56:13,100 keeping drinking the water and staying alive. 1146 00:56:13,100 --> 00:56:15,740 Mmm! Freshly synthesised water, delicious! 1147 00:56:15,740 --> 00:56:19,780 And I think, actually, it's time for you to all have some 1148 00:56:19,780 --> 00:56:22,580 freshly synthesised water, as well. 1149 00:56:22,580 --> 00:56:25,900 So you may have noticed that all around the lecture theatre 1150 00:56:25,900 --> 00:56:27,940 here is this very long tube. 1151 00:56:27,940 --> 00:56:30,980 This is over half a kilometre of tubing, 1152 00:56:30,980 --> 00:56:35,700 filled with hydrogen and oxygen in the right proportions to make water. 1153 00:56:35,700 --> 00:56:38,500 So we're going to synthesise some water now. 1154 00:56:38,500 --> 00:56:41,900 So I need the end of the tubes, please. OK, here they come. 1155 00:56:41,900 --> 00:56:44,020 Excellent. Thank you very much. 1156 00:56:44,020 --> 00:56:46,500 APPLAUSE 1157 00:56:50,940 --> 00:56:52,980 OK, now, the ends have some corks in 1158 00:56:52,980 --> 00:56:55,740 and we don't want to fire these into our audience, 1159 00:56:55,740 --> 00:56:58,620 so we're going to fire them into this bucket of water. 1160 00:56:58,620 --> 00:57:00,940 AUDIENCE: Aw! HE LAUGHS 1161 00:57:00,940 --> 00:57:04,100 No, don't say "Aw!" - you wouldn't want this! I can assure you! 1162 00:57:04,100 --> 00:57:06,900 Right, OK. But before I do this, though, 1163 00:57:06,900 --> 00:57:09,180 before we do this final thing here, 1164 00:57:09,180 --> 00:57:11,620 I hope you don't feel too disappointed 1165 00:57:11,620 --> 00:57:15,100 that we haven't found the secret to eternal youth. 1166 00:57:15,100 --> 00:57:18,220 But we have discovered a whole host of exciting elements 1167 00:57:18,220 --> 00:57:19,860 in that one glass of water. 1168 00:57:19,860 --> 00:57:21,940 Some of these elements were deadly toxic 1169 00:57:21,940 --> 00:57:24,140 and others were explosive metals. 1170 00:57:24,140 --> 00:57:26,740 In the next lecture, we're going to find out 1171 00:57:26,740 --> 00:57:30,780 how chemists are trying to extract exciting elements from the Earth. 1172 00:57:30,780 --> 00:57:32,780 These are elements that have been 1173 00:57:32,780 --> 00:57:35,140 trapped in rocks for billions of years. 1174 00:57:35,140 --> 00:57:36,580 And we'll also try to solve 1175 00:57:36,580 --> 00:57:38,820 the biggest alchemical mystery of them all, 1176 00:57:38,820 --> 00:57:41,460 how to turn lead into gold. 1177 00:57:41,460 --> 00:57:43,340 But before we finish, though, 1178 00:57:43,340 --> 00:57:47,820 I think it's time for everyone to get their freshly synthesised water. 1179 00:57:47,820 --> 00:57:49,100 So we'll have... 1180 00:57:49,100 --> 00:57:51,260 Yes, I need to move this from here! 1181 00:57:51,260 --> 00:57:55,420 OK, and we'll have a countdown from three when you're ready. 1182 00:57:55,420 --> 00:57:57,460 So we're just going to aim these. 1183 00:57:57,460 --> 00:57:59,540 And if we have the lights down? OK. 1184 00:57:59,540 --> 00:58:02,980 So, you might want to be looking up, rather than down at us. 1185 00:58:02,980 --> 00:58:04,980 OK, you look up at the pipe. 1186 00:58:04,980 --> 00:58:07,020 OK, so, three, two, one! 1187 00:58:08,300 --> 00:58:11,380 EXPLOSION SCREAMS 1188 00:58:11,380 --> 00:58:13,820 HE LAUGHS Thank you very much! 1189 00:58:13,820 --> 00:58:16,420 APPLAUSE AND CHEERING Good night, thank you! 1190 00:58:44,820 --> 00:58:48,860 Subtitles by Red Bee Media Ltd