1 00:00:17,033 --> 00:00:19,336 Why does this matter? 2 00:00:19,336 --> 00:00:21,404 We go back to the pteropod. 3 00:00:21,404 --> 00:00:23,073 And by the way, I didn't have this link, 4 00:00:23,073 --> 00:00:25,775 and I should have when I showed you the-- 5 00:00:25,775 --> 00:00:27,677 and this is your goody bag, et cetera. 6 00:00:27,677 --> 00:00:29,279 There's some really nice articles 7 00:00:29,279 --> 00:00:31,614 here that you can find related to these experiments 8 00:00:31,614 --> 00:00:34,484 and other things about ocean acidity in case 9 00:00:34,484 --> 00:00:36,319 you're interested. 10 00:00:36,319 --> 00:00:39,756 But see, what I did was that this was my 11 00:00:39,756 --> 00:00:41,291 why this matters on Monday. 12 00:00:41,291 --> 00:00:44,661 And I wanted to tell you about the goody bag and about 13 00:00:44,661 --> 00:00:49,566 how things dissolve, because Monday was about dissolving 14 00:00:49,566 --> 00:00:52,002 and finding a saturation point. 15 00:00:52,002 --> 00:00:55,138 Now we can get to the next place, which is, 16 00:00:55,138 --> 00:00:58,942 why does that matter for the pteropod's shell? 17 00:00:58,942 --> 00:01:02,278 What is the chemistry that matters there? 18 00:01:02,278 --> 00:01:05,749 OK, so I made the ocean a little more acidic. 19 00:01:05,749 --> 00:01:06,950 Why does that matter? 20 00:01:06,950 --> 00:01:09,352 But you see, now we're armed with the knowledge we 21 00:01:09,352 --> 00:01:10,820 need to answer that question. 22 00:01:10,820 --> 00:01:11,821 Now we're armed with it. 23 00:01:11,821 --> 00:01:15,091 All we need to do, as always with everything in life, 24 00:01:15,091 --> 00:01:16,793 is look at the chemistry. 25 00:01:16,793 --> 00:01:18,461 That's it. 26 00:01:18,461 --> 00:01:21,197 Say that at the Thanksgiving table. 27 00:01:21,197 --> 00:01:23,033 You'll be very popular. 28 00:01:23,033 --> 00:01:26,536 We said CO2 plus H2O. 29 00:01:26,536 --> 00:01:34,577 This goes-- oh, find some equilibrium to H2CO3. 30 00:01:34,577 --> 00:01:36,279 Now, this is called carbonic acid. 31 00:01:42,018 --> 00:01:43,553 This is called carbonic acid. 32 00:01:43,553 --> 00:01:45,288 There's the pteropod up there. 33 00:01:45,288 --> 00:01:47,424 And there's the reaction that's really relevant 34 00:01:47,424 --> 00:01:49,759 that you'll see from the ones we're about to write down. 35 00:01:49,759 --> 00:01:51,027 Why? 36 00:01:51,027 --> 00:01:55,231 Because the thing is that, what happens to carbonic acid? 37 00:01:55,231 --> 00:02:01,371 Well, carbonic acid also goes through a dissolution reaction. 38 00:02:01,371 --> 00:02:05,175 So this is CO2 dissolving in water. 39 00:02:05,175 --> 00:02:09,711 So carbonic acid goes like this. 40 00:02:09,711 --> 00:02:15,852 OK, it goes into HCO3- plus H+. 41 00:02:19,656 --> 00:02:21,257 Now, here's the thing. 42 00:02:21,257 --> 00:02:23,359 OK, what is the shell made of? 43 00:02:23,359 --> 00:02:30,333 Well, the shell that's dissolving, the core material 44 00:02:30,333 --> 00:02:32,001 is calcium carbonate. 45 00:02:32,001 --> 00:02:35,138 So that's CaCO3. 46 00:02:35,138 --> 00:02:36,272 That's the shell. 47 00:02:36,272 --> 00:02:40,577 And the shell also has an equilibrium reaction 48 00:02:40,577 --> 00:02:41,945 that happens. 49 00:02:41,945 --> 00:02:46,916 The shell of a sea creature is in dynamic equilibrium 50 00:02:46,916 --> 00:02:48,451 with the ocean. 51 00:02:48,451 --> 00:02:50,019 And so it's going like this. 52 00:02:50,019 --> 00:03:00,330 It's going to, well, OK, Ca2+ and CO3 2-. 53 00:03:00,330 --> 00:03:03,299 OK, but the thing is, it has an equilibrium constant. 54 00:03:03,299 --> 00:03:06,536 All these have equilibrium constants. 55 00:03:06,536 --> 00:03:10,473 So for example, for this one, the Ksp, 56 00:03:10,473 --> 00:03:12,208 the solubility product constant-- 57 00:03:12,208 --> 00:03:13,409 because this is a solid. 58 00:03:13,409 --> 00:03:16,478 This is the solid shell, solid, going 59 00:03:16,478 --> 00:03:18,047 to ions in aqueous solution. 60 00:03:20,783 --> 00:03:25,155 So the Ksp for that is somewhere around 5 times 10 61 00:03:25,155 --> 00:03:28,958 to the minus ninth, 5 times 10 to the minus ninth. 62 00:03:28,958 --> 00:03:30,093 Yeah, but here's the thing. 63 00:03:30,093 --> 00:03:32,362 We just went through this. 64 00:03:32,362 --> 00:03:36,031 If I consume one of these or change the concentration of one 65 00:03:36,031 --> 00:03:39,702 of these and not the other-- 66 00:03:39,702 --> 00:03:40,537 we just did this. 67 00:03:40,537 --> 00:03:42,338 If I could change the concentration, 68 00:03:42,338 --> 00:03:46,976 if I consume any of these, then I might drive the reaction-- 69 00:03:46,976 --> 00:03:48,711 consume or produce. 70 00:03:48,711 --> 00:03:51,514 If I change any of these independently, 71 00:03:51,514 --> 00:03:54,784 I'm going to drive the reaction, because that's 72 00:03:54,784 --> 00:03:58,788 how we keep to our K. That's what Le Chatelier's 73 00:03:58,788 --> 00:04:00,323 principle tells us. 74 00:04:00,323 --> 00:04:09,632 And so what ends up happening is you've got the extra H+ ions. 75 00:04:09,632 --> 00:04:11,601 So these are ions in solution. 76 00:04:11,601 --> 00:04:12,635 Where did they come from? 77 00:04:12,635 --> 00:04:16,139 They came from the CO2 giving us carbonic acid, 78 00:04:16,139 --> 00:04:17,906 which then gave us H+. 79 00:04:17,906 --> 00:04:19,841 Those are what I'm talking about. 80 00:04:19,841 --> 00:04:26,950 Well, they react with the CO3 2-. 81 00:04:30,587 --> 00:04:36,259 This lowers the CO3 2- concentration near the shell-- 82 00:04:36,259 --> 00:04:36,960 [STUDENT SNEEZES] 83 00:04:36,960 --> 00:04:37,659 --right? 84 00:04:37,659 --> 00:04:38,261 Gesundheit. 85 00:04:38,261 --> 00:04:40,897 And if I lower this, because I've taken some of this now 86 00:04:40,897 --> 00:04:44,234 and I've reacted it, so now I've got less of it. 87 00:04:44,234 --> 00:04:46,703 And because of what we just saw, if I've got less of this, 88 00:04:46,703 --> 00:04:50,106 you're going to drive this way, which is going 89 00:04:50,106 --> 00:04:53,810 to dissolve more of the shell. 90 00:04:53,810 --> 00:04:55,345 That's why this works. 91 00:04:55,345 --> 00:04:58,748 Well, that's why this happens. 92 00:04:58,748 --> 00:05:02,518 Works sounds like a positive thing. 93 00:05:02,518 --> 00:05:10,460 So this lowers the concentration of CO3 2-, 94 00:05:10,460 --> 00:05:17,734 and that drives more dissolution. 95 00:05:17,734 --> 00:05:19,168 That is what's happening. 96 00:05:19,168 --> 00:05:21,938 And we now can understand it in terms of the concepts 97 00:05:21,938 --> 00:05:24,907 that we've just learned. 98 00:05:24,907 --> 00:05:26,843 Historically, I mentioned 50 million years. 99 00:05:26,843 --> 00:05:29,312 Actually, by some accounts, it's 300 million. 100 00:05:29,312 --> 00:05:33,149 It depends on which studies you read. 101 00:05:33,149 --> 00:05:36,552 But for at least 50 and maybe as much as 300 million years, 102 00:05:36,552 --> 00:05:41,591 the ocean has had a pH of 8.18. 103 00:05:41,591 --> 00:05:45,128 Now, where's the-- oh. 104 00:05:45,128 --> 00:05:56,205 So let's just say last, oh, 50 to 300 millionish years, 105 00:05:56,205 --> 00:06:02,945 the ocean pH was 8.18. 106 00:06:02,945 --> 00:06:09,852 And today, it's 8.07. 107 00:06:09,852 --> 00:06:17,994 And the prediction is that in 2100, it will be 7.8. 108 00:06:17,994 --> 00:06:20,296 Now, as we will see in a little bit-- 109 00:06:20,296 --> 00:06:22,065 and you say, what's pH? 110 00:06:22,065 --> 00:06:23,633 And many of you probably already know, 111 00:06:23,633 --> 00:06:26,035 but I will tell you what it is in a little bit. 112 00:06:26,035 --> 00:06:28,671 But because this is a logarithmic thing, 113 00:06:28,671 --> 00:06:30,940 this is a lot, right? 114 00:06:30,940 --> 00:06:33,609 Today the ocean is 25% more acidic 115 00:06:33,609 --> 00:06:36,412 than it's been in 300 millionish years. 116 00:06:36,412 --> 00:06:41,183 And in 2100, it will be 126% more acidic. 117 00:06:41,183 --> 00:06:47,190 That's why they use 7.8 in the experiments of the pteropods.