[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.69,0:00:02.28,Default,,0000,0000,0000,,- [Lecturer] Almost all\Nthe matter in the universe
Dialogue: 0,0:00:02.28,0:00:05.22,Default,,0000,0000,0000,,is made from a few, about\N100 different elements,
Dialogue: 0,0:00:05.22,0:00:07.89,Default,,0000,0000,0000,,kind of like how all the English words
Dialogue: 0,0:00:07.89,0:00:09.45,Default,,0000,0000,0000,,and sentences in all the books
Dialogue: 0,0:00:09.45,0:00:13.02,Default,,0000,0000,0000,,and poems are made from just 26 letters,
Dialogue: 0,0:00:13.02,0:00:14.25,Default,,0000,0000,0000,,and of course, some spaces.
Dialogue: 0,0:00:14.25,0:00:15.66,Default,,0000,0000,0000,,But what I love about this analogy
Dialogue: 0,0:00:15.66,0:00:17.13,Default,,0000,0000,0000,,is we can take it one step further.
Dialogue: 0,0:00:17.13,0:00:19.59,Default,,0000,0000,0000,,Just like how letters can\Ncombine in interesting ways
Dialogue: 0,0:00:19.59,0:00:22.23,Default,,0000,0000,0000,,to form lots and lots of words,
Dialogue: 0,0:00:22.23,0:00:24.81,Default,,0000,0000,0000,,these elements can combine\Nin some interesting ways
Dialogue: 0,0:00:24.81,0:00:28.02,Default,,0000,0000,0000,,to form substances,\Nwhat we call compounds,
Dialogue: 0,0:00:28.02,0:00:30.39,Default,,0000,0000,0000,,and that's what we wanna\Ntalk about in this video.
Dialogue: 0,0:00:30.39,0:00:32.31,Default,,0000,0000,0000,,Well, first things first,\Nhow did we figure out
Dialogue: 0,0:00:32.31,0:00:34.77,Default,,0000,0000,0000,,that elements can combine\Nto form compounds?
Dialogue: 0,0:00:34.77,0:00:37.56,Default,,0000,0000,0000,,Well, when we took naturally\Noccurring substances
Dialogue: 0,0:00:37.56,0:00:41.55,Default,,0000,0000,0000,,with metals in them, which\Nwe call ores, for example,
Dialogue: 0,0:00:41.55,0:00:42.99,Default,,0000,0000,0000,,cinnabar is an ore
Dialogue: 0,0:00:42.99,0:00:47.49,Default,,0000,0000,0000,,because it contains mercury metal in it.
Dialogue: 0,0:00:47.49,0:00:51.45,Default,,0000,0000,0000,,And when we heated it, we were\Nable to extract that metal,
Dialogue: 0,0:00:51.45,0:00:52.53,Default,,0000,0000,0000,,we were able to get that metal,
Dialogue: 0,0:00:52.53,0:00:54.28,Default,,0000,0000,0000,,so we were able to get\Nthe mercury out of it,
Dialogue: 0,0:00:54.28,0:00:57.51,Default,,0000,0000,0000,,and some other substances as well.
Dialogue: 0,0:00:57.51,0:00:58.86,Default,,0000,0000,0000,,From this, we were able to guess that,
Dialogue: 0,0:00:58.86,0:01:01.66,Default,,0000,0000,0000,,hey, look, cinnabar is\Nmade from the combination
Dialogue: 0,0:01:01.66,0:01:03.87,Default,,0000,0000,0000,,of different elements.
Dialogue: 0,0:01:03.87,0:01:05.97,Default,,0000,0000,0000,,So cinnabar is probably your compound.
Dialogue: 0,0:01:05.97,0:01:07.44,Default,,0000,0000,0000,,And there are other examples.
Dialogue: 0,0:01:07.44,0:01:09.33,Default,,0000,0000,0000,,For example, if you take the ore of gold,
Dialogue: 0,0:01:09.33,0:01:10.65,Default,,0000,0000,0000,,which we call calaverite
Dialogue: 0,0:01:10.65,0:01:12.78,Default,,0000,0000,0000,,Yeah, these ores have very fancy names.
Dialogue: 0,0:01:13.77,0:01:14.88,Default,,0000,0000,0000,,Then if you heat that up,
Dialogue: 0,0:01:14.88,0:01:17.92,Default,,0000,0000,0000,,we will be able to extract\Nmetal, the gold out of it
Dialogue: 0,0:01:17.92,0:01:19.77,Default,,0000,0000,0000,,and some other elements as well.
Dialogue: 0,0:01:19.77,0:01:22.77,Default,,0000,0000,0000,,And again, you can see\Ntherefore calaverite,
Dialogue: 0,0:01:22.77,0:01:24.96,Default,,0000,0000,0000,,this ore is a combination\Nof these elements,
Dialogue: 0,0:01:24.96,0:01:26.46,Default,,0000,0000,0000,,and that's how we are able to guess
Dialogue: 0,0:01:26.46,0:01:28.86,Default,,0000,0000,0000,,that elements can combine\Ntogether to form compounds.
Dialogue: 0,0:01:28.86,0:01:30.78,Default,,0000,0000,0000,,And that's also the reason\Nwhy the periodic table
Dialogue: 0,0:01:30.78,0:01:31.92,Default,,0000,0000,0000,,does not have these compounds,
Dialogue: 0,0:01:31.92,0:01:34.92,Default,,0000,0000,0000,,because they are not\Nfundamentally new elements.
Dialogue: 0,0:01:34.92,0:01:36.01,Default,,0000,0000,0000,,These are the elements,
Dialogue: 0,0:01:36.01,0:01:39.66,Default,,0000,0000,0000,,and these are formed by\Ncombination of elements.
Dialogue: 0,0:01:39.66,0:01:41.91,Default,,0000,0000,0000,,But of course, let's be very concrete now.
Dialogue: 0,0:01:41.91,0:01:44.43,Default,,0000,0000,0000,,What exactly are compounds?
Dialogue: 0,0:01:44.43,0:01:46.29,Default,,0000,0000,0000,,Well, we define compounds are substances
Dialogue: 0,0:01:46.29,0:01:49.30,Default,,0000,0000,0000,,which are made from chemical combinations
Dialogue: 0,0:01:49.30,0:01:52.66,Default,,0000,0000,0000,,of two or more different elements.
Dialogue: 0,0:01:52.66,0:01:55.35,Default,,0000,0000,0000,,For example, if you look\Nat water, it's a compound
Dialogue: 0,0:01:55.35,0:01:57.45,Default,,0000,0000,0000,,because it's made from\Nthe chemical combination
Dialogue: 0,0:01:57.45,0:02:00.66,Default,,0000,0000,0000,,of two elements, hydrogen and oxygen.
Dialogue: 0,0:02:00.66,0:02:02.19,Default,,0000,0000,0000,,But what does it mean?
Dialogue: 0,0:02:02.19,0:02:03.36,Default,,0000,0000,0000,,What does it mean to say
Dialogue: 0,0:02:03.36,0:02:05.91,Default,,0000,0000,0000,,that they are a chemical combination?
Dialogue: 0,0:02:05.91,0:02:07.98,Default,,0000,0000,0000,,Well, for that, let's zoom into it.
Dialogue: 0,0:02:07.98,0:02:09.18,Default,,0000,0000,0000,,If you could zoom into water
Dialogue: 0,0:02:09.18,0:02:11.22,Default,,0000,0000,0000,,and look at the smallest bit of water,
Dialogue: 0,0:02:11.22,0:02:13.01,Default,,0000,0000,0000,,then we would see something like this.
Dialogue: 0,0:02:13.01,0:02:17.61,Default,,0000,0000,0000,,We would find that one\Noxygen atom is combined,
Dialogue: 0,0:02:17.61,0:02:21.00,Default,,0000,0000,0000,,it's connected to two\Nother hydrogen atoms.
Dialogue: 0,0:02:21.00,0:02:25.44,Default,,0000,0000,0000,,This is what we call a molecule of water.
Dialogue: 0,0:02:25.44,0:02:27.69,Default,,0000,0000,0000,,But what keeps these atoms together?
Dialogue: 0,0:02:27.69,0:02:29.22,Default,,0000,0000,0000,,Why are they connected like this?
Dialogue: 0,0:02:29.22,0:02:30.99,Default,,0000,0000,0000,,Well, it turns out that\Natoms can have a force
Dialogue: 0,0:02:30.99,0:02:32.70,Default,,0000,0000,0000,,of attraction between them.
Dialogue: 0,0:02:32.70,0:02:33.99,Default,,0000,0000,0000,,And this force of attraction
Dialogue: 0,0:02:33.99,0:02:36.45,Default,,0000,0000,0000,,is what we call a chemical bond.
Dialogue: 0,0:02:36.45,0:02:37.35,Default,,0000,0000,0000,,Again, don't worry too much
Dialogue: 0,0:02:37.35,0:02:40.53,Default,,0000,0000,0000,,about where this chemical bond\Ncomes from and all of that.
Dialogue: 0,0:02:40.53,0:02:42.54,Default,,0000,0000,0000,,We'll study more about that\Nin high school chemistry.
Dialogue: 0,0:02:42.54,0:02:45.30,Default,,0000,0000,0000,,But what's important is that\Nwhen atoms combine like this,
Dialogue: 0,0:02:45.30,0:02:48.25,Default,,0000,0000,0000,,that's what we call as\Na chemical combination.
Dialogue: 0,0:02:48.25,0:02:51.74,Default,,0000,0000,0000,,And so look, water is\Na chemical combination
Dialogue: 0,0:02:51.74,0:02:54.90,Default,,0000,0000,0000,,of two or more different elements.
Dialogue: 0,0:02:54.90,0:02:57.18,Default,,0000,0000,0000,,And so it's made of billions
Dialogue: 0,0:02:57.18,0:02:59.29,Default,,0000,0000,0000,,and trillions of these molecules.
Dialogue: 0,0:02:59.29,0:03:00.99,Default,,0000,0000,0000,,Let's take another example.
Dialogue: 0,0:03:00.99,0:03:02.34,Default,,0000,0000,0000,,If we consider carbon dioxide,
Dialogue: 0,0:03:02.34,0:03:05.34,Default,,0000,0000,0000,,which we usually find in\Nsmoke, then we'll find
Dialogue: 0,0:03:05.34,0:03:09.96,Default,,0000,0000,0000,,that it's made of two\Nelements, carbon and oxygen.
Dialogue: 0,0:03:09.96,0:03:12.39,Default,,0000,0000,0000,,And again, if we could zoom into it
Dialogue: 0,0:03:12.39,0:03:14.39,Default,,0000,0000,0000,,and look at the smallest\Nbit of carbon dioxide,
Dialogue: 0,0:03:14.39,0:03:16.29,Default,,0000,0000,0000,,this is what we would find.
Dialogue: 0,0:03:16.29,0:03:20.94,Default,,0000,0000,0000,,We would again find that look,\None carbon atom is connected
Dialogue: 0,0:03:20.94,0:03:24.30,Default,,0000,0000,0000,,to two other oxygen\Natoms forming a molecule
Dialogue: 0,0:03:24.30,0:03:25.20,Default,,0000,0000,0000,,of carbon dioxide.
Dialogue: 0,0:03:25.20,0:03:28.02,Default,,0000,0000,0000,,And again, it's a chemical combination.
Dialogue: 0,0:03:28.02,0:03:31.47,Default,,0000,0000,0000,,And that's why carbon\Ndioxide is a compound.
Dialogue: 0,0:03:31.47,0:03:35.43,Default,,0000,0000,0000,,It's called dioxide because\Nthere are two oxygen atoms.
Dialogue: 0,0:03:35.43,0:03:37.14,Default,,0000,0000,0000,,Okay, let's take one last example.
Dialogue: 0,0:03:37.14,0:03:39.22,Default,,0000,0000,0000,,If you were to look at the\Nsmallest bit of oxygen,
Dialogue: 0,0:03:39.22,0:03:40.95,Default,,0000,0000,0000,,you would see something like this.
Dialogue: 0,0:03:40.95,0:03:44.28,Default,,0000,0000,0000,,Two oxygen atoms are combined\Ntogether to form a molecule.
Dialogue: 0,0:03:44.28,0:03:46.13,Default,,0000,0000,0000,,So do you think oxygen is a compound?
Dialogue: 0,0:03:47.13,0:03:49.98,Default,,0000,0000,0000,,Well, remember, compounds\Nrequire chemical combination
Dialogue: 0,0:03:49.98,0:03:52.80,Default,,0000,0000,0000,,of two or more different elements.
Dialogue: 0,0:03:52.80,0:03:55.71,Default,,0000,0000,0000,,This is a chemical combination\Nof the same element,
Dialogue: 0,0:03:55.71,0:03:58.48,Default,,0000,0000,0000,,and therefore this is not a compound.
Dialogue: 0,0:03:58.48,0:04:00.45,Default,,0000,0000,0000,,Okay, now that we understand\Nwhat compounds are,
Dialogue: 0,0:04:00.45,0:04:03.21,Default,,0000,0000,0000,,let's finally see how to\Nwrite their chemical formulas.
Dialogue: 0,0:04:03.21,0:04:04.17,Default,,0000,0000,0000,,So if we go back to water,
Dialogue: 0,0:04:04.17,0:04:06.67,Default,,0000,0000,0000,,we saw that oxygen atom is connected
Dialogue: 0,0:04:06.67,0:04:09.39,Default,,0000,0000,0000,,to two other hydrogen atoms, right?
Dialogue: 0,0:04:09.39,0:04:10.59,Default,,0000,0000,0000,,So guess what?
Dialogue: 0,0:04:10.59,0:04:12.27,Default,,0000,0000,0000,,This ratio stays the same.
Dialogue: 0,0:04:12.27,0:04:14.43,Default,,0000,0000,0000,,One oxygen atom will always be connected
Dialogue: 0,0:04:14.43,0:04:16.50,Default,,0000,0000,0000,,to two other hydrogen atoms
Dialogue: 0,0:04:16.50,0:04:18.24,Default,,0000,0000,0000,,when it comes to a water molecule.
Dialogue: 0,0:04:18.24,0:04:19.77,Default,,0000,0000,0000,,And so the way we write this
Dialogue: 0,0:04:19.77,0:04:22.23,Default,,0000,0000,0000,,is we write the chemical formula as H2O.
Dialogue: 0,0:04:23.88,0:04:27.03,Default,,0000,0000,0000,,Notice that the two over here\Nis written as a subscript,
Dialogue: 0,0:04:27.03,0:04:30.52,Default,,0000,0000,0000,,which represents that there are\Ntwo hydrogen atoms connected
Dialogue: 0,0:04:30.52,0:04:33.30,Default,,0000,0000,0000,,to one oxygen atom.
Dialogue: 0,0:04:33.30,0:04:36.30,Default,,0000,0000,0000,,We'll not write it as H2O2, or HO.
Dialogue: 0,0:04:36.30,0:04:37.29,Default,,0000,0000,0000,,This would be all wrong.
Dialogue: 0,0:04:37.29,0:04:40.71,Default,,0000,0000,0000,,And fun fact, H2O2 is\Ncalled hydrogen peroxide,
Dialogue: 0,0:04:40.71,0:04:42.08,Default,,0000,0000,0000,,which is poisonous,
Dialogue: 0,0:04:42.08,0:04:45.24,Default,,0000,0000,0000,,which is ironic because\NH2O, which is water,
Dialogue: 0,0:04:45.24,0:04:48.37,Default,,0000,0000,0000,,it gives us life, but add\None more oxygen atom to it,
Dialogue: 0,0:04:48.37,0:04:50.31,Default,,0000,0000,0000,,it becomes poisonous.
Dialogue: 0,0:04:50.31,0:04:53.43,Default,,0000,0000,0000,,Okay, similarly, if you were\Nto look at the chemical formula
Dialogue: 0,0:04:53.43,0:04:54.99,Default,,0000,0000,0000,,for carbon dioxide,
Dialogue: 0,0:04:54.99,0:04:58.29,Default,,0000,0000,0000,,because I have one carbon\Nattached to two oxygen atoms,
Dialogue: 0,0:04:58.29,0:05:01.59,Default,,0000,0000,0000,,and that will always be the\Nfixed ratio for carbon dioxide.
Dialogue: 0,0:05:01.59,0:05:04.44,Default,,0000,0000,0000,,The way we'll write this is CO2.
Dialogue: 0,0:05:04.44,0:05:06.92,Default,,0000,0000,0000,,Again, notice we have written\Ntwo over here as a subscript
Dialogue: 0,0:05:06.92,0:05:11.40,Default,,0000,0000,0000,,because one carbon is\Nattached to two oxygen atoms.
Dialogue: 0,0:05:11.40,0:05:14.52,Default,,0000,0000,0000,,And we can have much bigger molecules.
Dialogue: 0,0:05:14.52,0:05:17.52,Default,,0000,0000,0000,,If you have ever put, sugar in lemonade,
Dialogue: 0,0:05:17.52,0:05:20.16,Default,,0000,0000,0000,,then you worked with a\Nmolecule called sucrose.
Dialogue: 0,0:05:20.16,0:05:21.51,Default,,0000,0000,0000,,It is a big molecule.
Dialogue: 0,0:05:21.51,0:05:24.69,Default,,0000,0000,0000,,And let's now look at its\Nchemical formula, C11H22O11.
Dialogue: 0,0:05:27.00,0:05:28.35,Default,,0000,0000,0000,,So this tells us
Dialogue: 0,0:05:28.35,0:05:29.88,Default,,0000,0000,0000,,that there are 11 carbon atoms
Dialogue: 0,0:05:29.88,0:05:34.02,Default,,0000,0000,0000,,attached to 22 hydrogen atoms,\Nattached to 11 oxygen atoms.
Dialogue: 0,0:05:34.02,0:05:36.78,Default,,0000,0000,0000,,This is one single molecule of sucrose.
Dialogue: 0,0:05:36.78,0:05:38.60,Default,,0000,0000,0000,,All right, putting it all together,
Dialogue: 0,0:05:38.60,0:05:40.20,Default,,0000,0000,0000,,all matter in this universe
Dialogue: 0,0:05:40.20,0:05:42.63,Default,,0000,0000,0000,,is made from a few, about\N100 different elements.
Dialogue: 0,0:05:42.63,0:05:45.18,Default,,0000,0000,0000,,And when these different elements combine
Dialogue: 0,0:05:45.18,0:05:48.01,Default,,0000,0000,0000,,together chemically, we get compounds.
Dialogue: 0,0:05:48.01,0:05:50.61,Default,,0000,0000,0000,,The ratio of the elements is always fixed
Dialogue: 0,0:05:50.61,0:05:51.45,Default,,0000,0000,0000,,in these compounds,
Dialogue: 0,0:05:51.45,0:05:54.45,Default,,0000,0000,0000,,and that's represented by\Nthese chemical formulae.
Dialogue: 0,0:05:54.45,0:05:57.03,Default,,0000,0000,0000,,And these compounds can be\Nrepresented by these molecules,
Dialogue: 0,0:05:57.03,0:05:59.94,Default,,0000,0000,0000,,which act like a single unit over here.