1 00:00:00,000 --> 00:00:00,560 2 00:00:00,560 --> 00:00:03,580 In the last video we touched on the three states of matter 3 00:00:03,580 --> 00:00:06,990 that are really most familiar to our everyday experience. 4 00:00:06,990 --> 00:00:12,410 The solid, the liquid, and the gas. 5 00:00:12,410 --> 00:00:14,910 And I kind of hinted that there is a fourth state, which 6 00:00:14,910 --> 00:00:17,309 I don't cover, because it's usually not the domain of an 7 00:00:17,309 --> 00:00:18,559 introductory chemistry course. 8 00:00:18,559 --> 00:00:20,750 But a little bit of a discussion ensued on the 9 00:00:20,750 --> 00:00:22,339 message board for that video. 10 00:00:22,339 --> 00:00:24,910 So I thought I would at least touch on that fourth stage. 11 00:00:24,910 --> 00:00:26,579 And that's plasma. 12 00:00:26,579 --> 00:00:30,969 I'll do it in a suitably bright color. 13 00:00:30,969 --> 00:00:32,039 Plasma. 14 00:00:32,039 --> 00:00:34,109 And people consider it a fourth state because it has 15 00:00:34,109 --> 00:00:36,479 some properties of gases. 16 00:00:36,479 --> 00:00:39,429 In some ways it's almost a subset of gases. 17 00:00:39,429 --> 00:00:42,880 But it also has properties of conductivity that you normally 18 00:00:42,880 --> 00:00:46,350 wouldn't associate with a gas. 19 00:00:46,350 --> 00:00:50,100 And just so you know, when you first hear it you think, oh 20 00:00:50,100 --> 00:00:52,990 that's a fairly exotic thing, plasma. 21 00:00:52,990 --> 00:00:55,450 And in the first video, I said it's only something that 22 00:00:55,450 --> 00:00:56,690 occurs at high temperatures, which isn't 23 00:00:56,689 --> 00:00:58,369 exactly 100% right. 24 00:00:58,369 --> 00:01:00,119 It doesn't have to be at high temperatures. 25 00:01:00,119 --> 00:01:02,729 I really should have said that under extenuating 26 00:01:02,729 --> 00:01:04,670 circumstances where you have a very strong 27 00:01:04,670 --> 00:01:06,040 electromagnetic field. 28 00:01:06,040 --> 00:01:10,550 Or something has to happen to essentially bump the the 29 00:01:10,549 --> 00:01:14,579 electrons, or move the electrons off of gases that 30 00:01:14,579 --> 00:01:16,409 would've otherwise have kept their electrons. 31 00:01:16,409 --> 00:01:18,539 So it's kind of analogous to what happens in metal. 32 00:01:18,540 --> 00:01:21,170 When we talk about metal bonds, we talk about this 33 00:01:21,170 --> 00:01:23,469 notion of a sea of electrons. 34 00:01:23,469 --> 00:01:26,150 Let's say if we talked about iron. 35 00:01:26,150 --> 00:01:30,130 What happens with most metals is that they have so many 36 00:01:30,129 --> 00:01:33,219 electrons, and they are so willing to give them, that the 37 00:01:33,219 --> 00:01:37,989 electrons just kind of float outside of the atoms 38 00:01:37,989 --> 00:01:41,250 themselves and create this kind of big sea of electrons. 39 00:01:41,250 --> 00:01:43,760 And then the atoms themselves become 40 00:01:43,760 --> 00:01:47,109 positively charged ions. 41 00:01:47,109 --> 00:01:49,019 Because they essentially donated some 42 00:01:49,019 --> 00:01:49,869 electrons to the sea. 43 00:01:49,870 --> 00:01:52,219 So they're attracted to the sea and that's what makes them 44 00:01:52,219 --> 00:01:54,480 malleable and even more importantly what allows them 45 00:01:54,480 --> 00:01:55,510 to conduct electricity. 46 00:01:55,510 --> 00:01:58,300 But they're all really packed closely together and it's a 47 00:01:58,299 --> 00:01:59,709 very dense structure. 48 00:01:59,709 --> 00:02:03,319 Plasma is a situation where if you take gases, and remember, 49 00:02:03,319 --> 00:02:05,639 in gases things are pretty far apart. 50 00:02:05,640 --> 00:02:07,700 So you take a bunch of gases and they have 51 00:02:07,700 --> 00:02:08,699 high kinetic energy. 52 00:02:08,699 --> 00:02:12,340 Although, they don't have to be, that could be under very 53 00:02:12,340 --> 00:02:12,969 low pressure. 54 00:02:12,969 --> 00:02:14,949 But they're moving around and bumping into each other. 55 00:02:14,949 --> 00:02:16,739 But they're not close to each other. 56 00:02:16,740 --> 00:02:19,450 They don't have a fixed structure with each other. 57 00:02:19,449 --> 00:02:21,139 Or they're not rubbing against each other like in 58 00:02:21,139 --> 00:02:22,429 the case of a liquid. 59 00:02:22,430 --> 00:02:26,159 But what happens in a plasma, or one situation is, that you 60 00:02:26,159 --> 00:02:29,770 apply such a strong electromagnetic field that the 61 00:02:29,770 --> 00:02:32,460 electrons want to disassociate. 62 00:02:32,460 --> 00:02:34,129 So let's say these electrons start 63 00:02:34,129 --> 00:02:37,219 bumping off of the plasma. 64 00:02:37,219 --> 00:02:40,530 And so a solid has its own shape. 65 00:02:40,530 --> 00:02:43,300 A plasma will take the shape of its container like a gas. 66 00:02:43,300 --> 00:02:46,350 And sometimes it is described as an ionized gas. 67 00:02:46,349 --> 00:02:47,810 And it's described as ionized because 68 00:02:47,810 --> 00:02:49,849 electrons are bumped off. 69 00:02:49,849 --> 00:02:52,319 And when the electrons are bumped off, the otherwise 70 00:02:52,319 --> 00:02:57,310 neutral atoms now have positive charges. 71 00:02:57,310 --> 00:02:59,830 And what this allows is, essentially a conduction of 72 00:02:59,830 --> 00:03:00,450 electricity. 73 00:03:00,449 --> 00:03:02,959 Because now these electrons are free to move. 74 00:03:02,960 --> 00:03:06,460 You might say that sounds like a bizarre state of matter, 75 00:03:06,460 --> 00:03:07,550 where does it exist? 76 00:03:07,550 --> 00:03:10,930 Well, probably closest to home, it exists in lightning. 77 00:03:10,930 --> 00:03:13,939 78 00:03:13,939 --> 00:03:16,579 And that's worthy of an entire video. 79 00:03:16,580 --> 00:03:19,300 But the idea is that you start having a huge potential 80 00:03:19,300 --> 00:03:22,765 difference between the clouds and the ground. 81 00:03:22,764 --> 00:03:26,149 82 00:03:26,150 --> 00:03:28,480 And then because you have this huge voltage difference 83 00:03:28,479 --> 00:03:31,709 between the two, you have electrons that are essentially 84 00:03:31,710 --> 00:03:35,090 wanting to go into the ground. 85 00:03:35,090 --> 00:03:42,400 You have a build-up of electrons up here that want to 86 00:03:42,400 --> 00:03:44,270 go into the ground. 87 00:03:44,270 --> 00:03:46,870 They can't because air is normally 88 00:03:46,870 --> 00:03:50,390 a fairly bad conductor. 89 00:03:50,389 --> 00:03:51,250 It's an insulator. 90 00:03:51,250 --> 00:03:53,490 But what happens is because there's so much 91 00:03:53,490 --> 00:03:56,540 electropotential here, the electrons that are close in 92 00:03:56,539 --> 00:04:01,099 the molecules up here, at least how I visualize it, 93 00:04:01,099 --> 00:04:04,889 their electrons want to escape from these clouds. 94 00:04:04,889 --> 00:04:06,979 So their electrons start to want to move 95 00:04:06,979 --> 00:04:09,299 away in the air molecules. 96 00:04:09,300 --> 00:04:11,130 Whether you're talking about the air is a mixture of 97 00:04:11,129 --> 00:04:13,750 oxygen, and nitrogen, and carbon dioxide. 98 00:04:13,750 --> 00:04:15,780 They start wanting to get away from the clouds. 99 00:04:15,780 --> 00:04:19,079 So they start disassociating and start forming 100 00:04:19,079 --> 00:04:20,949 this ionized air. 101 00:04:20,949 --> 00:04:24,519 And eventually, at some point, this happens to such a degree 102 00:04:24,519 --> 00:04:28,209 that you can actually get conduction from the cloud to 103 00:04:28,209 --> 00:04:29,609 the ground. 104 00:04:29,610 --> 00:04:35,850 And that conduction is when the air is in a plasma state. 105 00:04:35,850 --> 00:04:38,550 The conduction allows extremely high temperatures 106 00:04:38,550 --> 00:04:41,620 and the electrons to flow all the way to the ground. 107 00:04:41,620 --> 00:04:44,750 The other common example, you might see something like this, 108 00:04:44,750 --> 00:04:47,410 well actually not like this, but at least a plasma state, 109 00:04:47,410 --> 00:04:48,360 is in stars. 110 00:04:48,360 --> 00:04:50,389 And that's because you have extremely strong 111 00:04:50,389 --> 00:04:54,399 electromagnetic fields, extremely high pressure, and 112 00:04:54,399 --> 00:04:58,479 in that type of environment, once again, I'm old super over 113 00:04:58,480 --> 00:05:00,870 simplifying it, you can get to a state where the electrons 114 00:05:00,870 --> 00:05:04,579 can get disassociated from things that otherwise wouldn't 115 00:05:04,579 --> 00:05:05,620 want to give up their electrons. 116 00:05:05,620 --> 00:05:07,410 I thought I would touch on that because it's an 117 00:05:07,410 --> 00:05:08,470 interesting subject. 118 00:05:08,470 --> 00:05:11,820 And it exists in the universe. 119 00:05:11,819 --> 00:05:14,759 On the universal level, because stars are pretty much 120 00:05:14,759 --> 00:05:18,295 all plasma, it is actually the most common state of matter in 121 00:05:18,295 --> 00:05:19,000 the universe. 122 00:05:19,000 --> 00:05:22,410 Although in our everyday life, we probably encounter solids, 123 00:05:22,410 --> 00:05:24,420 liquids and gases a lot more. 124 00:05:24,420 --> 00:05:27,590 And one other thing I want to maybe clarify from the last 125 00:05:27,589 --> 00:05:29,299 video is, I talk about the bonding 126 00:05:29,300 --> 00:05:32,350 between water molecules. 127 00:05:32,350 --> 00:05:34,180 And let's say we're talking in the solid state. 128 00:05:34,180 --> 00:05:38,660 So I have an oxygen, a hydrogen, a hydrogen. 129 00:05:38,660 --> 00:05:41,720 And I have some electrons here, some electrons here. 130 00:05:41,720 --> 00:05:46,866 Let's say there's another hydrogen here, an oxygen, and 131 00:05:46,865 --> 00:05:48,069 a hydrogen. 132 00:05:48,069 --> 00:05:50,839 Maybe there's an oxygen here. 133 00:05:50,839 --> 00:05:52,125 That has hydrogen. 134 00:05:52,125 --> 00:05:58,709 135 00:05:58,709 --> 00:06:00,129 And then this has a hydrogen. 136 00:06:00,129 --> 00:06:03,370 And it has two electrons, two electron pairs. 137 00:06:03,370 --> 00:06:07,139 So I talked about the notion, and we talked about it many 138 00:06:07,139 --> 00:06:07,620 times before. 139 00:06:07,620 --> 00:06:10,139 That oxygen is so much more electronegative that it hogs 140 00:06:10,139 --> 00:06:11,349 the electrons. 141 00:06:11,350 --> 00:06:13,100 And so the oxygen side starts to have a 142 00:06:13,100 --> 00:06:15,060 partial negative charge. 143 00:06:15,060 --> 00:06:16,899 While the hydrogen side starts to have a 144 00:06:16,899 --> 00:06:17,949 partial positive side. 145 00:06:17,949 --> 00:06:19,420 Because with the hydrogen, essentially all of its 146 00:06:19,420 --> 00:06:23,730 electrons are hanging out close to the oxygen, hydrogen 147 00:06:23,730 --> 00:06:25,590 ends up just becoming like this proton that's 148 00:06:25,589 --> 00:06:26,129 floating out there. 149 00:06:26,129 --> 00:06:27,310 Because we said it doesn't even have 150 00:06:27,310 --> 00:06:29,180 neutrons in most cases. 151 00:06:29,180 --> 00:06:30,620 So this has a slightly positive charge. 152 00:06:30,620 --> 00:06:32,399 This one has a positive charge. 153 00:06:32,399 --> 00:06:38,560 And the positive polar end of the water molecule is 154 00:06:38,560 --> 00:06:40,290 attracted to the negative polar end. 155 00:06:40,290 --> 00:06:45,730 And I called it polar bonds, and it shows you my memory 156 00:06:45,730 --> 00:06:48,745 from high school chemistry is not ideal, I really should 157 00:06:48,745 --> 00:06:52,280 have called it hydrogen bonds. 158 00:06:52,279 --> 00:06:56,009 So this is a hydrogen bond, and this is a hydrogen bond. 159 00:06:56,009 --> 00:06:58,810 It's just a matter of the name I used. 160 00:06:58,810 --> 00:07:00,780 I just want to clarify that because that is what's 161 00:07:00,779 --> 00:07:02,479 typically used in your chemistry class. 162 00:07:02,480 --> 00:07:03,620 I don't want to confuse you. 163 00:07:03,620 --> 00:07:08,680 And that is just the bond that exists from a partially 164 00:07:08,680 --> 00:07:10,530 positive hydrogen atom. 165 00:07:10,529 --> 00:07:14,399 Because its electrons are hanging out near the oxygen. 166 00:07:14,399 --> 00:07:18,979 And a partially negative oxygen atom 167 00:07:18,980 --> 00:07:20,200 in the water molecule. 168 00:07:20,199 --> 00:07:22,920 Because it has stolen all of these 169 00:07:22,920 --> 00:07:24,580 electrons from the hydrogen. 170 00:07:24,579 --> 00:07:26,680 You draw it like that, it's called a hydrogen bond. 171 00:07:26,680 --> 00:07:31,959 And hydrogen bonds tend to form between hydrogen or 172 00:07:31,959 --> 00:07:35,739 really only a handful of super electronegative atoms. And 173 00:07:35,740 --> 00:07:40,500 that's nitrogen, fluorine, and oxygen. 174 00:07:40,500 --> 00:07:44,230 And these are actually the three most electronegative 175 00:07:44,230 --> 00:07:54,680 atoms. So the nitrogen, NH3, when it bonds with hydrogen, 176 00:07:54,680 --> 00:07:56,939 is essentially so electronegative that you have 177 00:07:56,939 --> 00:07:58,209 the same situation. 178 00:07:58,209 --> 00:08:00,409 All the electrons hang out here, so you have a partial 179 00:08:00,410 --> 00:08:04,770 negative charge, partial positive on the hydrogen ends. 180 00:08:04,769 --> 00:08:08,839 Same thing with hydrogen fluorine. 181 00:08:08,839 --> 00:08:11,409 You get the same HF. 182 00:08:11,410 --> 00:08:13,740 You get the same type of hydrogen bonds. 183 00:08:13,740 --> 00:08:17,280 And so in this case, these guys would be attracted to the 184 00:08:17,279 --> 00:08:19,189 nitrogen part of other molecules and would form 185 00:08:19,189 --> 00:08:19,819 hydrogen bonds. 186 00:08:19,819 --> 00:08:21,339 I just want to get that out of the way. 187 00:08:21,339 --> 00:08:23,719 And with that done, I think we can return to some of the 188 00:08:23,720 --> 00:08:31,200 ideas of the last video and actually do some problems. 189 00:08:31,199 --> 00:08:32,450 Let's take the case with water. 190 00:08:32,450 --> 00:08:36,950 191 00:08:36,950 --> 00:08:39,780 Actually, let me just state the problem first. So let's 192 00:08:39,779 --> 00:08:43,600 say that we have a 193 00:08:43,600 --> 00:08:44,802