This eighth-grade science lesson is about the chemical properties of metals and non-metals. It is the fourth lesson in a sequence of 30 lessons on elements and the Periodic Table. The lesson is 33 minutes in duration. There are 30 students in the class.

00:00:55Come on, come on. Right-o ladies and gents. Let's go back over yesterday. We talked about elements in the Periodic Table. We said that elements are matter.
00:01:14They are therefore composed of- they're therefore composed //of? Of particles.
00:01:21These particles are called?
00:01:25These particles are called molecules.
00:01:31These molecules are made of?
00:01:34Okay. Joined together by?
00:01:38By chemical bonds.
00:01:39By chemical bonds. Okay. Because they're- because elements are a pure substance.
00:01:51The same.
00:01:52All molecules are?
00:01:53The same.
00:01:54Are the same. We said yesterday in elements, what are the particles inside the molecules?
00:02:08Are called atoms. Inside the molecule are?
00:02:17The particles.
00:02:18The particles. What about the particles?
00:02:21They're all the same.
00:02:23They're the same. And we gave some examples. The examples we gave were these ones here in which there were?
00:02:33Three (inaudible).
00:02:34No. There were, these- these indicate.
00:02:38These indicate? No, they're- what are these?
00:02:40They're the molecules. Indicated that inside the molecule there is only?
00:02:49One atom. Those kinds of molecules are referred to as being?
00:02:56Monatomic. In these ones here there are-
00:03:03Two? Two.
00:03:04Two atoms inside the molecule, and these ones are referred to as being?
00:03:09Diatomic. These indicate- these- the Y's indicate the?
00:03:19The atoms. This line here indicates the-
00:03:24The chemical bond. And what exists between this molecule here and this molecule here? Some kind of?
00:03:37Some- Not a chemi- not a strong chemical bond but a?
00:03:40Weak. Different.
00:03:41But a different kind of bond that joins?
00:03:45Molecules together. What do we break when we melt an element?
00:03:50The bonds.
00:03:51We break- which bonds do we break? The ones inside or the ones between?
00:03:55The ones between. These ones here have got?
00:03:58Four atoms.
00:04:00Four atoms inside the molecule and therefore are called?
00:04:04Polyatomic- ah, Polly the parrot isn't it? So these are- right-o.
00:04:11What we've also got are elements that have got huge numbers, huge numbers of atoms inside each molecule, and they're going to be the metals. Okay.
00:04:24What we need to do is to look- go back to the periodic table from yesterday, and we come down here. Not a good spot for it, is it? I'd better bring that up the front. I thought you'd be further down.
00:05:02We said yesterday that these elements- these elements over here are?
00:05:08Are non-metals. They're the ones with
00:05:11One atom. Oh, they're gases. One atom in the molecule. These ones are- these ones have two atoms in the molecule. These ones here have- are polyatomic with small numbers, P four and S-A.
00:05:23Right. These are the non-metals. But carbon has got lots of atoms inside the molecule. All these ones over here are shiny and these ones over here are the?
00:05:34Are the metals. What we need to do now, and this is what this lesson's about. I want you to be able to find ways of distinguishing between metals and non-metals. All right?
00:05:46And there are two ways of doing it. Elements have physical properties which we'll be talking about in the future, but elements also have chemical properties.
00:05:58So we're going to look at the chemical properties of two non-metals, those two there, phosphorus and sulfur and we're going to look at a chemical property of this one here, which is magnesium, and this one here which is iron.
00:06:15All right. And the chemical property we're going to learn about is what happens when we burn them and then dissolve the product in water? Is that fair?
00:06:25Okay. What you- but- and the only way we're going to do that is by?
00:06:30Is by experiment. I can't tell you about it. You can only find out if you-
00:06:34Do //it.
00:06:35//Learn it. Now once we do it you've got a problem. The problem is that you have to write it down in a form that is- that you understand. Right?
00:06:48So not only do we have to do the experiment, and watch me do a demonstration over there, you have to write it down in a form that you understand. Okay? That's good for you.
00:06:59And we'll put- we'll put a summary on the blackboard. So, what I'd like you to do, we've got one, two, three, four, five groups.
00:07:07So what I'd like you to do is to get one of these trays and bring it back to your bench please, so could one person from this side pick up the trays and take one for this bench and one for that one please.
00:07:39What flame have I got it on?
00:07:43It's on the safety flame.
00:07:49We'll get that on in a sec. We need to share one between two-
00:08:17We're not-
00:08:18Do we need water?
00:08:19Oh we'll- you'll have to share that. I've got one lot of water between the two. Okay, now, what we're going to do is to burn some magnesium. The magnesium is the?
00:08:29(That bit).
00:08:30This piece, piece of wire. Magnesium is a very active metal and it burns very, very easily. Iron is not an active metal. If I used a piece of iron like that I couldn't get it to? I couldn't get it to burn.
00:08:42What I've got to use is a piece of iron which is steel wool which is very finely divided and then it will burn. I'm not going to be able to make it happen with that flame am I?
00:08:53So what flame are we going to have to change it to?
00:08:54Heat. Blue heat.
00:08:55So when we're going to do- when we do the heating we change it to the blue. All right? Second thing, magnesium burns with a very, very bright flame. You don't stare at it. All right?
00:09:06You can look and watch the flame. But don't stare at it. If you do it then you can hurt your eyes a little bit. All right. It also burns?
00:09:14Very hot. If it burns very hot what I don't want you to do is?
00:09:18Touch it.
00:09:19Touch it. Right, so in order to do that I've given you a pair of wooden tongs. All right. Anyway so don't- when I, when you put it in there I fold it over, fold it over so it makes a double piece like that.
00:09:35All right. Now. You also have a little beaker. I want you to put a piece in some water in the beaker. That's- oh, too much. About that much. And a few drops of universal indicator in it.
00:09:51And you'll need to share those b- those big beakers of water with the be- with the bench beside you. Right, put the universal indicator in now.
00:10:00How many drops?
00:10:01About four or five. Pass the water over please ladies... Right. When you put the universal indicator in, the universal indicator will be that colour.
00:10:16Right, that indicates that the unit- that the solution in there is neither acid nor alkaline, acid or basic. It is neutral. Okay. That's the green colour.
00:10:27Right-o. A few drops. Now. Next bit. I want you to turn the flame to the?
00:10:39Blue heat.
00:10:40To the heating flame. Away from the safety. You know how to do that. If you don't, you've forgotten from last year. Turn the air hole. Put the magnesium in the flame. Right.
00:10:56Once it starts to burn, look away and bring it over and put it over the top of the beaker. Right.
00:11:03This one or the-
00:11:04No, the little one. The one with all the stuff in it.
00:11:09Put it in, sir?
00:11:11Yep, once it's all burned, put a drop- undo- just unclip it and put it in. Has there been a change in colour?
00:11:28Yeah, it went a brighter green.
00:11:30A brighter green, I wouldn't have called it a brighter green. It's (inaudible), gone a bit.
00:11:35We've got to leave it there- oh hang on, we've stopped. Didn't burn it all. You panicked. Goodness gracious. Panic merchants.
00:11:45That's what you're going to be doing.
00:11:47What a chemist.
00:11:57I'm going to get a migraine tomorrow from this because the flames hurt my eyes. Okay, now, ladies and gents. Stop for a sec. Are we all done?
00:12:15You all done?
00:12:17We've got one more to do, sir
00:12:18I know that. Have we got the- have we burnt the magnesium? Have we put it into the solution? What colour has the solution gone?
00:12:25Green. Blue. Green.
00:12:26Has- it's gone a blue colour. Right?
00:12:28Yes. Yeah.
00:12:29Let it stand for a little while and as it- as it stands it will go blue. Let it stand for a little while. Right. The one that I did worked, look. Right, the one that I did worked. It's gone a blue colour.
00:12:43What does that indicate? That it's a?
00:12:46It's alkaline.
00:12:49Yep. That's just fine. Okay, can you come back, can you sit down please. No, whoops. That's all right. Hold it up, hold it up, hold it up. Let it burn. Move it forward a bit. Move it forward.
00:13:07Now let it drop. Let it drop. Good boy. Okay. Let it stand for a little while. What, to me please. Magnesiums combined with oxygen in the air to form a new compound called magnesium oxide.
00:13:30All right? What we're finding is now is what happens when that magnesium oxide dissolves in water. Fair? Not a problem? What I want to do now. Gentlemen. Watch me.
00:13:47You don't learn by watching that for the minute. I want to do now is to take a non-metal. We're going to take phosphorus and we're going to take sulfur. And I'm going to burn those.
00:13:57I don't want you to do it. The reason I don't want you to do it is I don't want to fill the room with?
00:14:02Smelly gasses.
00:14:03With smelly gasses. Right. So I'll do it over here. And the other thing is that I'll do it a f- the other thing is that I'll do it in a fume cupboard.
00:14:11And I'll do it in a fume cupboard so any excess fumes go-
00:14:13Up. (inaudible).
00:14:14Out into the atmosphere. Right, so over here.
00:14:29Now. What I'd like you to do, the people up the back, if you can come up to here please and say you- and sh-share the seats over here, or maybe come around the front.
00:14:49Turn the fume cupboard on so that we won't fill the air with noxious fumes. The other part of the problem is this little spoon is called a deflagrating spoon. Deflagrating is a word meaning?
00:15:07Burning. Right. It's got a lid on here that fits over the top of the gas jar. Right. So I'll start it burning-
00:15:28And phosphorus burns with a?
00:15:31White smoke?
00:15:32With a white smoke. Keep it burning in there. Right. Now what will happen is the white smoke, you got a white powder before?
00:15:45Yeah. Yes.
00:15:46The white smoke will now dissolve in the water.
00:15:49What happens when the white smoke-
00:15:52It goes red.
00:15:53It's gone red. What- what colour did metals go, when- when metals burnt they formed a?
00:15:59White powder. That white powder dissolved in water and made the- made the universal indicator go?
00:16:07Blue. The non-metals burn in air to form a white powder. That white powder dissolves in water to form a solu- a substance which turns that indicator red. That indicates that a substance is an acid.
00:16:22Right? For some reason- see why only one person did it? I've got the coughs. For some reason they call that white powder there is an- it's an oxide. It's called a, an acidic oxide. Why is it called an acidic oxide?
00:16:41(inaudible) acid.
00:16:42Because it dissolves in water to form an?
00:16:45Acid. Right. Just do that one. I'll put a bit more in so it's a bit more obvious. Second one is that this is another non-metal and I want to watch this one carefully. This one smells the worst.
00:16:59(inaudible) Rotten (inaudible) gas.
00:17:01It doesn't make rotten egg gas, it forms sulfur dioxide. And sulfur dioxide's a gas that's used in industry, particularly in the wine industry to- and the beer industry to- to sterilise bottles.
00:17:12It sterilises bottles because it kills any kind of bugs that are in there. Sulfur is a? Yellow powder. Now. The sulfur, oh hang on, what has it done?
00:17:27What's it done?
00:17:29How much te- how much heat did it take to melt it?
00:17:31Not much.
00:17:32Oh. What does that say about the bonds which are joining the molecules together?
00:17:37Not very strong.
00:17:38They're not very strong at all, they're easily broken. Okay? Now, to start it burning-
00:17:49It's started to boil now, and it's burning with a? Burning with a?
00:17:57What colour flame?
00:17:59Blue flame. Whoops. This is the one that's got to go in there. That's got to go in there because it's got a really bad smell.
00:18:13And the fume cupboard is not working particularly well and that's a bit of a problem. Sulfur burns in air to form? Tell me? Magnesium burnt to form? Magnesium oxide. Phosphorus burnt to form?
00:18:27Phosphorus //oxide.
00:18:28//Phosphorus oxide. Sulfur burns to form?
00:18:30Sulfuric //oxide.
00:18:31//Sulfur oxide. See the fumes coming out the top? Dissolves in water to form?
00:18:37Red (inaudible).
00:18:38Make it go red, the indicator go red, that- therefore is called an?
00:18:43An acidic oxide. It forms an acid. How can you tell the difference between- if these- sorry let's try again.
00:18:50If those two non-metals burn in there to form an oxide which dissolves to form an acid, what would you assume? That other non-metals will do?
00:19:00The same.
00:19:01The same thing. For example. Carbon's a non-metal. It burns in there to form?
00:19:08Carbon oxide.
00:19:09Carbon oxide. Carbon oxide dissolves in water to form? An acid. Do we ever use that acid? How many of you have seen carbonic acid? What a load of rubbish.
00:19:20You drink it every time you have a mouthful of coke. You drink it every time you have a mouthful of soft drink. You drink it every time you have a mouthful of? How do you make any kind of soft drink? Out of?
00:19:32Out of C-I beg your pardon?
00:19:33Carbonated water.
00:19:35What is the carb- what do you do to carbonate water? What do you do to carbonate water? You put into it?
00:19:42Carbon oxide. Carbon dioxide.
00:19:45Is that like when, um-
00:19:47Why does- sorry go on.
00:19:49The things where you make your own soft drinks with a gas bottles?
00:19:52How about that. What's inside those- what's inside those little bombs you put- you screw in the top?
00:20:01Dioxide. It dissolves in water to form? Carbonic acid, which you love. Right. No, you don't like it as soda water do you?
00:20:11But you do when you put some-
00:20:13Flavour in it.
00:20:14Some flavour in it. Okay. That makes sense?
00:20:18So how do we tell the difference be- how do we tell the che- what's the difference, chemical di- in chemical properties between a metal and a non-metal?
00:20:24Metals burn (inaudible).
00:20:26Ahh, metals burn in air to form?
00:20:29White powder.
00:20:30To form?
00:20:31White powder.
00:20:32That white powder. That white powder dissolves in water to form?
00:20:38A blue solution which is an alkaline. Right? That particular alkaline made in there is called milk of magnesia. What do they use milk of magnesia for?
00:20:51It's a medicine given to babies to cure... indigestion. Right?
00:20:57So it's not really strong.
00:20:59No, not real strong at all. You wouldn't give it to a baby to cure indigestion if it was real strong. What gives you indigestion? Too much?
00:21:07Ah, not too much food. What does your stomach make to digest the food?
00:21:12Acids. So why do you take milk of magnesia, or those things?
00:21:16Because (inaudible).
00:21:17Because it's alkaline that takes the acid away. Right. How do you make an acid?
00:21:22By burning a non-metal.
00:21:25By burning a non-metal and forming a white- an oxide. That oxide dissolves in water to form an acid. Any questions? Is there a distinct difference between metals and non-metals in their chemical properties?
00:21:38Yes. Yeah.
00:21:39Yes there is. Oh, guess what? Nature doesn't go one kind of substance, boom, new kind of substance. Non-metal, boom, metal. What do you think nature does? Ladies.
00:21:54Makes a mixture.
00:21:56No, it grades. So there are some of those metals on that per- ah, that table over there, which have got the properties of met- the chemical properties of metals, and the chemical properties of?
00:22:08Non-metals. And they're the ones which are in between and they're called amphoteric and we'll talk about those later on. Okay?
00:22:15Have you got the um, (inaudible) purple. (inaudible). Put-put one of them in because red and blue makes purple so we'd get purple.
00:22:21No, if we- if you put- both put some of that in and some of those in, that acid would use up that alkaline, and it would go back to being?
00:22:30Green. Back to be-go back to being neutral.
00:22:34Okey dokey. Would you like to go to sit down please, you need to put some stuff in your notebooks. Oh no, before we do that. Before we do that, can you rinse out those- those beakers down the sink.
00:22:47Rinse the beakers out down the sink. Put some more water in it. Rinse them out down the sink, put some more water in it. I think I'll have to open- open some windows.
00:23:00Sir, is there wa-
00:23:03No don't- no the water's here. A little rinse and guess- and change it- just swap some water over. Here we are. Rinse it out. Rinse it out, quick. Put some water in it. Put some indicator in it.
00:23:20Now what do you need to do? Now what do you need to do? You need to burn the steel wool, allow it to burn and then drop that into the water. Heh. Just pick it up in the tongs.
00:23:39Give it a- when you pick it up in the tongs, when you pick the steel wool up in the tongs, have it like that- right? Just pinch a little tiny bit at the end, put it in the flame, in the hot flame.
00:23:52Got to open the top. Oh my goodness, give it a blow on it. Heat it up and blow on it. Over the top. Blow on it, blow on it. I've turned that he- the heater off, Bunsen off, didn't I?
00:24:10Give it a good burn. Does it form a white powder?
00:24:19Does it form a white powder?
00:24:21No (inaudible).
00:24:22No, it forms a?
00:24:25A blacky kind of powder. Anyone know what that powder is called?
00:24:30Not iron but we- we had magnesium form magnesium oxide, sulfur forms?
00:24:36It's called iron oxide. Right. Another name for iron oxide is? Rust. Put it now into the water and see what happens. See if it changes colour... Put it- give it another heat. Has it all burnt?
00:24:56Oh. It will now. Okay, now put it in.
00:25:07It stays green.
00:25:08It stayed green? Goodness. Ladies and gents-
00:25:13It stayed green.
00:25:14To me please, to me please... To me please. Did it go- did it stay green?
00:25:29Yeah. Yes.
00:25:30Oh. Does iron oxide form an alkaline?
00:25:36No. Alkali- metal ox- listen time. Listen time. Metal oxides that dissolve in water form alkalies and that are bases, right, they form alkalies.
00:25:53Metal oxides which don't dissolve in water are simply called bases. Right? They're not alkalies because they don't dissolve. This one doesn't dissolve. Because it doesn't dissolve, what doesn't it do?
00:26:06Doesn't change.
00:26:07Doesn't change the colour. Right? In fact-
00:26:12What did we-what did we say the Periodic Table form is for?
00:26:15To make it easier.
00:26:16Make it easier to learn about?
00:26:19Elements. Right-o. See these ones here, this group down here and this group down here, they're the ones that form the alkalies.
00:26:28They're the ones when you burn them they form an oxide that dissolves in water and makes that water go blue, right, or purple.
00:26:36All of these ones over here, they just burn in there to form an oxide and they don't make it turn blue. Is that fair? But they're still called ba- er gives us- it's a chemical word, we call them?
00:26:49A base. Anybody got a problem? Okay, what have we got to work out now?
00:26:57I beg your pardon?
00:26:59We've got to work out what we're going to put in our books don't we? Right? Do I write that?
00:27:04No. No.
00:27:05No way. Who writes that?
00:27:07We do.
00:27:08We do in a form that you can-
00:27:11Understand. It's 12:43. What time's the bell go?
00:27:20About (inaudible).
00:27:23The (inaudible) bell sheet //over there.
00:27:25Mr.(inaudible), (inaudible).
00:27:33Okay. We said that-
00:27:49Oh, where have I put my chalk? Where did I put my chalk... Where did I put my chalk? Sorry Dave. Can you hang on- can you hang on for a minute.
00:28:10Okey dokey.
00:28:12We're having our lesson video taped. Right-o ladies and gents. Ladies and gents, watch.
00:28:24Metals do what? You can turn the Bunsens off if you like. Metals do what?
00:28:31They- no don't put them- you just turn it off. Metals do what?
00:28:37When we heat them up what do they do?
00:28:39They went white.
00:28:41They burn in air-
00:28:50To form a substance called, a new substance called an?
00:28:54An oxide. What have they reacted with?
00:29:08Why- what have they reacted with to form an oxide?
00:29:30Right-o. What- I won't- won't call it an oxide, I'll call it a metal. What did some of those do? What did some of those do? Dissolved in water to form a?
00:29:51Ah, ah, ah. What colour did it make it go? With the metals?
00:29:55Made it went blue, therefore it forms an?
00:29:58An alkali. Dissolves in water-
00:30:09To form an alkali. Is that //fair? Right-o-
00:30:19Non-metals do what? Non-metals do what?
00:30:25Burn in air.
00:30:26Burn in air to form a?
00:30:28(inaudible). Acid.
00:30:30No, no, no. They burn- metals burn in air to form a new substance called a?
00:30:34Metal oxide.
00:30:35A metal oxide. Non-metals burn in air to form a new substance called a? Oh, dear oh dear oh dear. Metals form- burn in air to form a new substance called a metal oxide.
00:30:51Non-metals burn in air to form a?
00:30:54Non-metal oxide.
00:30:55A non-metal oxide. Thank you.
00:31:04Because they have reacted with the oxygen in the air. Right? These ones dissolve in water... to form what?
00:31:19An acid
00:31:21An acid. How do we know?
00:31:24Because they went red.
00:31:26Because the indicator turned?
00:31:28Red. And when we compare it with the scale it means it's acid. Okay. Therefore, what do we call a metal oxide? What do we call a metal oxide?
00:31:43It's not a- what's the special word I used instead of alkali? //Started
00:31:47Base. So this one's called a-
00:31:54And this one dissolves in any metal to form an acid so it's called an... it's called an?
00:32:03Acid oxide.
00:32:05It's called an acid oxide. Now your work to do now, there's the summary. How do we use that to tell the difference between metals and non-metals of chemical properties?
00:32:20How do we use that information to tell the difference between metals and non-metals? Yep.
00:32:25You burn the non-metals (inaudible)
00:32:28It will form an, yeah.
00:32:31(inaudible) alkaline.
00:32:32Absolutely. Not a problem. Okay. What have you got- what's your homework? Two sets. Number one, describe the experiments we've done.
00:32:45Number two, make a general statement about what we've just learned. Any problems? Ladies and gentlemen thank you for your attention. Do you want to go to maths now?
00:33:09Are you right? What time's this bell go?
00:33:16Five minutes.
00:33:17About five minutes... This is, the writing part is groupwork. Right? This is not me, this is groupwork, so it's time for you now to get organised within your group to write down what you've- what we've learned. What?
00:33:34What's the second part?
00:33:36Second part of the- huh, first part was to describe the experiment. Second part was to say what we- indicate what- how do we tell the difference between metals and non-metals.
00:33:55Sorry, yep?
00:33:58I've got some um (inaudible) universal reactors.
00:34:01Not a problem. Just rinse it off with a bit of water. Just go to the tap and rinse it off with a bit of water.
00:34:06It's not a problem, it's only methylated spirits on you.
00:34:08Oh so it's okay.
00:34:09Not a problem. Yep.