# CZ2 SALTS

This eighth-grade science lesson is about chemical compounds. It is the 10th lesson in a sequence of 12 lessons on salts. The lesson is 45 minutes in duration. There are 30 students in the class.

TimeCaption
00:00:03I'm going to-
00:00:05Why don't we all stand up. Please be quiet. You may sit down.
00:00:17I would like to find out, who's missing?
00:00:21So, that will be- (Novakova) and (Kolarova).
00:00:27(Novakova) and (Kolarova).
00:00:58Today, we're going to start off, by giving someone an oral quiz. It's going to be (Straka). Take the chalk and stand up behind the blackboard.
00:01:09(Stojkova) is next. (Stojkova). Please take the chalk and stand behind the second part of the blackboard.
00:01:21(Terner) and (Vojtikova). You two will write up at the front of the blackboard.
00:01:25The entire class will open their notebooks from the back. Everyone else- as always, we'll write formulas.
00:01:38Okay, let's begin. Is everyone ready? I would also like to divide the class into two groups of A and B.
00:01:56Okay, let's begin. Calcium chloride, calcium chloride.
00:02:09Potassium sulphite, potassium sulphite, potassium sulphite.
00:02:26The next formula is, ammonium bicarbonate, ammonium bicarbonate, ammonium bicarbonate.
00:02:54The next formula is, copper sulfate.
00:03:23The last formula is very difficult. It's called, sodium tetraborate, sodium tetraborate.
00:04:14Those of you who are sitting alone, can offer their work to anybody in the class. Okay, we're finished.
00:04:25Now, we're going to correct and check our work. Let's start with the students, who are up here by the board.
00:04:37The first one is calcium chloride. Which formula is correct and which one isn't?
00:04:46CaCl2.
00:04:47CaCl2. What about here- why did you write CaCl? Why did you write CaCl? Can you explain it to us?
00:05:01Because I thought that the oxidation value of the chlorine is negative one.
00:05:06Very good. So, you knew that the oxidation value of calcium is two and the oxidation value chlorine is negative one. Very good.
00:05:18How about the second formula. Okay?
00:05:35Sulphite-
00:05:38//K2SO3.
00:05:40Is it correct, everyone?
00:05:42Yes.
00:05:43Yes. Okay, both formulas are correct. This was supposed to be ammonium bicarbonate. Which one of those formulas is correct?
00:05:54Is it correct? Did one of them, write it correctly?
00:05:56This one, here. Dusan's.
00:05:58Yes. So-
00:05:59I have it in the inside.
00:06:01This formula is correct, this formula is incorrect. Completely wrong. Okay? The next formula is supposed to be anhydrous copper sulfate. Is it correct?
00:06:14Yes.
00:06:15Yes, it is. This one is not even here. And the last one is sodium tetraborate. Is this formula correct?
00:06:26Yes, yes.
00:06:28Those of you that agree with him, please raise your hand. Okay, good.
00:06:33Sodium tetraborate is okay because the oxidation value of boron is-
00:06:38Three.
00:06:39Three. Very good and let's sit down. Now, we'll assign grades. Okay.
00:06:46All these formulas here were correct. We'll give an A grade. This one has two incorrect and one is missing so we'll give it a C grade.
00:07:05On this side of the board- we'll just confirm the formulas. Correct, correct, correct. This one is also correct, yes? This one is also correct.
00:07:17This student gets an A. And here? This student gets an A as well. Everything is correct. So that one gets the letter grade A and so does this one.
00:07:29Please step away from the board. Now, everybody in class, please open your books. Group A, will look up page 114. There is a table, number nine.
00:07:56Please fill out the table with your pencil. Okay? Group B of the class, turns to page 118.
00:08:05It's the assignment number five and there is a table. Fill it out with your pencil as well.
00:08:12And those of you up here, we will continue. I will ask you some questions and you will answer them. Okay? Fertilizers.
00:08:23Fertilizers are actually-
00:08:26They are substances, which give nutrients to living plants and soil, during the vegetation growth.
00:08:36During the vegetation growth. Can you name some fertilizers?
00:08:41Mineral fertilizers.
00:08:42Mineral fertilizers. Can you think of other fertilizers?
00:08:45Organic fertilizers.
00:08:46Organic fertilizers. Can you name some organic fertilizers?
00:08:48Those can be found on ranches and farms.
00:08:50And they are?
00:08:52Manure, sewage.
00:08:55Sewage.
00:08:57And wastewater.
00:09:00The wastewater. Are there any other organic fertilizers, which you can name?
00:09:04No. You've mentioned all of them. What is a mineral fertilizer? Do you know of any mineral fertilizers?
00:09:10Potassium chloride, for example?
00:09:14Yes, it may be potassium chloride. But what about some different ones, can you name any?
00:09:21Crushed limestone.
00:09:23Crushed limestone, excellent. What fertilizers, other than organic, do you know of?
00:09:28Industrial fertilizers.
00:09:29Industrial fertilizer. Can you name a few?
00:09:31Those are-
00:09:32The rest of you, must do your work quietly.
00:09:36Single element fertilizers and the multiple elements fertilizers.
00:09:38Single element fertilizers and the multiple elements fertilizers. Name some single element fertilizers?
00:09:42Phosphate, nitrogen, and potassium.
00:09:48Potassium fertilizers, yes. Nitrogen, phosphate- please do your work quietly. Okay, next one.
00:09:57The ceramic industry, creates ceramics. What kind of ceramics do we know?
00:10:04The standard kind, for example.
00:10:05The standard. What is considered the standard ceramics?
00:10:09The (inaudible).
00:10:17Okay. What is considered the standard ceramics? Please name a few, for us?
00:10:22The sink.
00:10:24The sink, for instance.
00:10:25Tiles.
00:10:26Tiles, tiles.
00:10:28Toilets.
00:10:29Toilet sinks, correct. Anything else? What other ceramics do you know?
00:10:34Rough ceramics.
00:10:35Rough ceramics. Name some rough-
00:10:37Rough ceramics. Those are mostly ceramics, which are used in construction. Roof tiles, for example.
00:10:44Roof tiles. Can you think of other items? How would we categorize pottery, for instance?
00:10:53Those fall under rough ceramics.
00:10:56It falls under rough ceramics as well. Are there other ceramics?
00:11:00It could be plates or (inaudible) and vases.
00:11:06Okay. What are these items made of?
00:11:12Clay and (glass).
00:11:15We've said that the fine ceramic is made out of what? Of what?
00:11:22Kaolin.
00:11:23It's made out of kaolin. Yes. It's made out of kaolin. What is the kaolin? What is the kaolin? Is it being mined in the //Czech Republic?
00:11:31//Yes.
00:11:32Yes, what is produced- it's clay, which is being mined in this country. At what part of the country is kaolin being mined?
00:11:42The Czech Heights.
00:11:45Well, around major cities. Can you name a city?
00:11:49Karlovy Vary.
00:11:50Karlovy Vary, for instance. Very good. Now everyone, grab a piece of chalk because you will write your grade.
00:12:00This student gets a B grade, you get an A, you get a B and you get an A. Those are your grades.
00:12:09And for the final evaluation, please write some chemical reactions. How about the reaction of hydrochloric acid with sodium hydroxide.
00:12:20Hydrochloric acid plus sodium hydroxide. Sodium hydroxide. Everyone is doing it on their own. Sodium hydroxide. Okay.
00:12:34Do you know how to complete the chemical reaction?
00:12:42Okay? Underneath that, please write, what type of reaction is it? What kind of reaction is it?
00:12:56Okay. Very good, very good.
00:13:09And it is a neutralization. This one is correct. Very good. You may go back to your seats and I'll give you your grades.
00:13:16So, I think (Straka) will get an A because he did a remarkable job. Next student is (Terner), he will also get an A.
00:13:34(Stojkova).
00:13:35(Stojkova) gets a lower A grade and...
00:13:41(Vojtikova).
00:13:42(Vojtikova) also gets an A minus. Over all, it was pretty good. Please sit down.
00:13:53Okay. Now I would like to ask the entire class- on page one- 114. The table. Which of you did not fill it out?
00:14:08Obviously, those of you, that were up here, did not do the table. Did anyone not complete it? Did anyone have difficulties with anything?
00:14:15No? Okay. You did? Okay, what's the problem?
00:14:19Bluestone.
00:14:20The bluestone. What is it that you don't know? The chemical formula?
00:14:24Yes. No, the chemical name.
00:14:26The chemical name. Which of you knows the chemical name of the bluestone?
00:14:31Copper sulfate pentahydrate.
00:14:32Copper sulfate pentahydrate. Come up here and write up the formula. Copper sulfate pentahydrate.
00:14:40May I take this book with me?
00:14:41No, just come up here to the board really fast, so you don't waste time. Copper sulfate pentahydrate.
00:14:52Okay. So the only thing that you had trouble with was the name, bluestone.
00:14:57Yes.
00:14:58Okay. Please sit down. Very good. The second table graph, letter B. It's on page 118. Which of you had trouble with this one?
00:15:10Okay, which one?
00:15:11The common name for calcium sulfate hemihydrate.
00:15:14Okay. Calcium sulfate hemihydrate. Who knows the name of- hemi means, half of something.
00:15:23Plaster.
00:15:24Yes, it is plaster. It's a baked plaster. Okay, we all write the baked plaster in our tables. Any other problems?
00:15:33Okay. We-
00:15:35The name of potassium permanganate.
00:15:36The name of potassium permanganate. Wait a minute, we can already derive that one, we already have the formula of KMNO4. Which one is it?
00:15:45Manganese potassium.
00:15:46Excellent. It's the manganese potassium.
00:15:49Okay, I'm not going to go over your correct answers because I want you to use the answers in the following table, which we'll be working on.
00:16:01In this class, we have to discuss the use of the salts and the chemical reactions with salts. Okay. Please erase the board, erase the board, quickly.
00:16:24While he's erasing the blackboard, we can distribute the following tables. Okay? Here, distribute these all over the classroom.
00:16:37You, as well. Let's speed it up. Why don't you distribute these as well?
00:17:02No, no. That's enough.
00:17:19Okay. In our previous lesson, we've introduced the chemical nomenclature of salts, how to write the formulas, and what some of the salts look like.
00:17:29And today, we'll finalize all this information and we'll complete the table, which is in front of you.
00:17:38I will turn off the lights, so we can take a look- everyone can orient themselves, so I know where-
00:17:48We'll view the table on the overhead projector. Everyone will orient themselves. Okay. Everyone at the same time.
00:18:02Here we have the first salt. What is the first salt called? Who can tell us?
00:18:08Potassium chloride.
00:18:09Potassium chloride. It's here. Can we write the formula?
00:18:14KCl.
00:18:15KCl. Please fill in KCl in the- into the table. Potassium chloride. Do you know the common name or do you know the name of the mineral in which-
00:18:30Rock salt.
00:18:31No, it's not rock salt. Potassium chloride or sylvine. Okay, so why don't you write sylvine, sylvine. It's a mineral, which is potassium chloride.
00:18:54The next thing is, coming up with an example of the usage. Can you recall a situation, where the potassium chloride can-
00:19:02Industrial fertilizer.
00:19:03Yes, it is the industrial fertilizer. Why don't you write, industrial fertilizer. Okay.
00:19:13KOH can be also produced from it. What is the KOH?
00:19:17Potassium hydroxide.
00:19:18Potassium hydroxide. Very good. Please write, KOH. Okay. The next- the next one is?
00:19:29(inaudible).
00:19:30We have NaCl. What is it?
00:19:33Sodium chloride.
00:19:34Sodium chloride. Yes. The name of this formula is sodium chloride.
00:19:41Can anyone tell me the common name or mineral?
00:19:48Rock salt.
00:19:49Rock salt. Have you ever seen it?
00:19:52Yes.
00:19:53Where have you seen it?
00:19:55In the household.
00:19:56In the household, which is in the kitchen. I brought you a large piece of salt. I'm sure, you've never seen this kind before.
00:20:03Here, take a look. This large piece is only one crystal.
00:20:06We've seen this before.
00:20:07You've seen this in your geology class, for instance. Okay. So this is a solid salt crystal. Yes. Beautiful crystal.
00:20:19Very good. Okay, what is the salt being used for?
00:20:24In the household.
00:20:25At home as seasoning. What else is it used for?
00:20:32For cleaning of the surface of the metals.
00:20:34I don't think so. I would say-
00:20:39For animals?
00:20:40Food additive for animals. But what can be produced from it? Some kind of hydroxide. What kind?
00:20:49Sodium.
00:20:50The sodium, yes. Why don't you write, the production of KOH- NaOH. Good. The next salt on the list is? Let's take a look.
00:21:03Ammonium chloride. Please take good notes because this table will be used as the review. Everything you write in, you must memorize. Okay.
00:21:16Ammonium chloride. What is the formula for that?
00:21:19NH4Cl.
00:21:20Excuse me?
00:21:22NH4Cl.
00:21:23NH4Cl. Yes. NH4Cl. Do you know the common name?
00:21:30Sal ammoniac.
00:21:31Sal ammoniac. Very good. Sal ammoniac. Can someone tell me- has anybody seen the sal ammoniac? The look of it?
00:21:41(Maybe).
00:21:42No, you haven't seen it. I brought these tools here, to show you how easily it can be produced. What is the sal ammoniac produced from, what do you think? Take a look here.
00:21:55(inaudible).
00:21:57Yes. So, we're going to use hydrochloric acid.
00:22:00Hydrochloric.
00:22:01Hydrochloric acid. Let's take a look here. The hydrochloric acid. I'm pouring a small amount, into the graduated cylinder. It only takes a very small amount.
00:22:16And what is the second matter, we'll be using?
00:22:19Ammonia.
00:22:20Ammonia, very good. It's also called ammonium hydroxide. Yes. Ammonium hydroxide. Take a look what is being created. It's going to be sal ammoniac.
00:22:34Take a look. Do you see it? Here it is.
00:22:41It's very beautiful. So these white vapors are sal ammoniac. Okay?
00:22:48Is it poisonous?
00:22:49Well it's not poisonous. But- are you familiar with term sal ammoniac, what is it used for? I have already heard it here-
00:23:00For cleaning.
00:23:01Yes, very good. For cleaning. I will cover the beaker, so it doesn't stink up the room. Okay. Sal ammoniac.
00:23:15What is the next salt, is on the list?
00:23:20Sodium nitrate. Sodium nitrate is poisonous. What is the formula? Everyone will write the formula. Please write it down. You wrote it down already?
00:23:32NaNO3.
00:23:34NaNO3 is sodium nitrate. Okay.
00:23:38Is it poisonous? I got it mixed up with silver sodium. I was ahead of myself. The sodium nitrate is not poisonous.
00:23:47But it's- what is the common name for it? What is it?
00:23:53Saltpeter.
00:23:54Saltpeter. Very good. It's saltpeter. Why don't you write saltpeter?
00:23:59Okay. Nitrate- where is saltpeter being used?
00:24:04Fertilizer.
00:24:05The saltpeter fertilizer. Very good. Why don't you write, saltpeter as the fertilizer. Okay?
00:24:13In the table, we'll skip potassium nitrate because it's very similar to the previous one. Okay? Just tell me the formula.
00:24:22KNO3.
00:24:24KNO3. Fill in your table for potassium nitrate. The silver nitrate. The formula for that is? Please raise your hands.
00:24:38AgNO3.
00:24:39AgNO3. Is everyone keeping up with the writing? Yes. The silver nitrate. Where can we find that?
00:24:49Caustic.
00:24:50Caustic. What does caustic mean?
00:24:52Warts.
00:24:53For warts. Correct. So, where is it being used?
00:24:57The pharmacy.
00:24:58In medicine, for example. Yes, in medicine.
00:25:02Why don't you, Jonasi, read the next formula, which is in the table. It's this one. It's this formula.
00:25:13(inaudible)?
00:25:16Yes.
00:25:17CuSO4, 5H2O.
00:25:19Can you read the written format?
00:25:21Copper sulfate pentahydrate.
00:25:25Copper sulfate pentahydrate. Correct. Everyone will write, copper sulfate pentahydrate. What is the name of it?
00:25:37Blue vitriol.
00:25:38Blue vitriol. Did you all see blue vitriol? I took the opportunity to bring in- show you from the laboratory, these crystals or blue vitriol.
00:25:54Why don't you take a look at this beautiful-
00:25:56We've done that as well.
00:25:57You've experimented with this matter already? During-
00:25:59During our chemical experimenting.
00:26:00During your chemical experimenting. Okay. That's how blue vitriol looks like, which you observed this summer in your study.
00:26:11Where is blue vitriol being used?
00:26:14For controlling the growth, for example.
00:26:15Excuse me?
00:26:16For controlling the growth, for example.
00:26:17Very good. Why don't you write... you can even write, disinfectant products against mold or the controlling of growth against mold.
00:26:30And as metal coating, for instance. Okay? We have the word green below that. Yes? What word is missing there? What is-
00:26:41Green vitriol.
00:26:42Green vitriol. What actually, is green vitriol? There is a formula of FeSO4 times 7H2O. How would you read that?
00:26:56Iron sulfate heptahydrate.
00:26:58Iron sulfate heptahydrate. Very good. Who has seen the green vitriol? No one. It's a good thing that I brought it with me.
00:27:09Unfortunately, I left it upstairs, so I don't have it here. It's green and very similar to the crystal matter. It's used against the moss. Okay?
00:27:22Why don't you write, the moss. Okay, the next one is CaSO4. CaSO4 times 2H2O. How do we read the formula, for that one?
00:27:34Not everyone has been raising their hands. How about back there. Shirek?
00:27:38Calcium sulfate.
00:27:39Excuse me?
00:27:40Calcium sulfate.
00:27:41But the 2? H2O?
00:27:44Calcium sulfate dihydrate.
00:27:45Calcium sulfate dihydrate. Yes. What is the common name? Dehydrated-
00:27:53Gypsum.
00:27:54It is gypsum. Correct. It is gypsum. What is gypsum used for?
00:28:03The production of plaster.
00:28:04The production of plaster. Let's all write, the production of plaster. The production of plaster.
00:28:12Very good. The next one is, sodium carbonate. What is the formula for sodium carbonate?
00:28:21Na2CO3.
00:28:22Na2CO3. Na2CO3. Which of you have seen the word, soda.
00:28:30(inaudible).
00:28:31Soda. That's the common name. So, the common name is soda. But be careful. Soda must have what?
00:28:43(inaudible).
00:28:44Excuse me? It must include water. Now I want to show all of you the soda. I brought it with me.
00:28:55So it's- it's not- soda is a crystal matter. Here, take a look at the soda. Please take a look at the soda.
00:29:06What does it look like? How would you characterize it?
00:29:10White, powder.
00:29:12White, without color. White, crystallized matter. Okay?
00:29:17Everyone can see the soda. What is soda used for?
00:29:22The production of soap.
00:29:24The production of soap. Very good. So, why don't you all write the production of soap? //Anywhere else?
00:29:28//Glass.
00:29:29The glass. Excellent. Is it also being used somewhere in the household?
00:29:33Softening water.
00:29:34The softening of water. Okay. So, the softening of hard water. Okay?
00:29:48The next one is? The formula is, NaHCO3. What is that?
00:29:55Sodium hydrogen carbonate.
00:29:56Sodium hydrogen carbonate. Sodium hydrogen carbonate. Does anybody know- did someone come across it?
00:30:06Sodium bicarbonate.
00:30:07Sodium bicarbonate. Very good. Sodium bicarbonate. Good observation. Excuse me?
00:30:13The common name.
00:30:14Well, we can use it as the common name. Sodium bicarbonate. Has anyone used sodium bicarbonate? What is it good for?
00:30:24For the stomach.
00:30:25To prevent stomach acid. Good. The prevention of stomach acid.
00:30:32We're going to skip the carbonated potassium because it's being used for- we'll leave it alone. Calcium carbonate. Calcium carbonate?
00:30:44CaCO3.
00:30:45CaCO3.Everyone should write, CaCO3. What is the name of the carbonate- as a mineral? How about you.
00:30:56Calcium.
00:30:58Me?
00:30:59Yes.
00:30:59Calcium.
00:31:00Or what's the other word?
00:31:01Limestone.
00:31:02So that is a mineral.
00:31:03Mountain limestone.
00:31:04Mountain limestone. Yes, the limestone. Can someone tell me- we've already seen the solidification of cement, slaked lime?
00:31:18So, what is it used for? What is the limestone used for?
00:31:22Burned lime.
00:31:24Burned lime. So, why don't you write, the burning of lime.
00:31:29Can someone tell me, what the burned lime is? What is it?
00:31:34CaO.
00:31:35CaO. You've had geology, earlier today. Correct?
00:31:38Yes.
00:31:39In your previous class. I wanted to ask you, didn't you also learn-
00:31:44Limestone.
00:31:45Limestone. And what is created from the limestone?
00:31:48(inaudible).
00:31:49The limestone or the karst-like process. Yes? Do you know the main reason for the karst-like process?
00:31:57Sun and... limestone precipitates out.
00:31:59Well, limestone precipitates, it creates calcite. And what grows from that? //Stalagmite.
00:32:06//Stalagmite
00:32:07Yes. The stalagmite grows from it. What else do we- I brought a sample. I'm sure you've seen it before, but I brought some //limestone here, just in case.
00:32:19//Is it the chalk?
00:32:20It is not a chalk. It's the limestone. It's white limestone. Okay?
00:32:29The next one on the list is the second to last. It's KMnO4. What does that mean?
00:32:38Potassium manganate.
00:32:39Potassium manganate. Potassium manganate. What is it- from the table?
00:32:48Potassium permanganate.
00:32:49Potassium permanganate. It is given in the table. Potassium permanganate.
00:32:55Do you know what potassium permanganate- you may have heard it somewhere. What is it used for?
00:33:02As a disinfectant and oxidizing agent. Write down, disinfectant and oxidizing agent.
00:33:31Calcium phosphate.
00:33:33Calcium phosphate. Calcium phosphate. What is the common name for it? Do you know?
00:33:41Apatite.
00:33:42Well, the super phosphate is commonly used. It's a mineral, whose name is?
00:33:48Apatite
00:33:49Apatite. Phosphate, apatite. Phosphate and apatite.
00:34:02I would like to return to the potassium permanganate. I brought one, for you to see. You probably can't see it.
00:34:10I'm going to demonstrate- yes it dissolves into a purple liquid.
00:34:19Let's take a look here, at this Petri dish and I'm going to place several crystals and pour in some water.
00:34:39It is very interesting.
00:34:42Very good. What kind liquid is it? You can all see that it's-
00:34:49Pink color.
00:34:50The pink liquid. This has disinfecting qualities.
00:34:55In the civilian world, for example, kids are taught to use potassium permanganate, for disinfecting masks and so on.
00:35:12Do you see it? We're not going to add anymore. You can see, it's a pink liquid. Okay?
00:35:22I think we're done with the table. Why don't you study the table? The next topic is, the reaction.
00:35:32I had prepared another table. I would like you to take a look at it. It is a very difficult theme. Can you see it?
00:35:53Yes.
00:35:54Okay. I'm sure, you're going to recognize the formulas. Let's go over it. Can somebody tell me what that is? The chemical formula.
00:36:06Calcium carbonate.
00:36:07Calcium carbonate. And what is this?
00:36:09Calcium oxide.
00:36:10Calcium oxide. Can someone write up the equation? How calcium carbonate turns into calcium oxide. Go up to the board and write the formula.
00:36:22In the meantime, you'll write the formula into your notebooks. Write the formula into your notebooks.
00:36:35CaCO3.
00:36:38Here is number two.
00:36:40It derives- so the arrow should be pointing, what direction?
00:36:43Is the calcite created from that? What is created from that?
00:36:48You need to reverse it. Yes. Okay.
00:36:54I'm going to turn on the light, so we can have more light.
00:37:03Okay. CO2 is created and what is CaO?
00:37:07(inaudible).
00:37:08Calcium oxide and what else?
00:37:11Carbon dioxide.
00:37:13Carbonated, yes. I would like to ask you kids, what is the common name for CaO? What is the common name for CaO?
00:37:22We should see more hands up. We've already covered this material.
00:37:27Okay. (Antolova)?
00:37:30Burned lime.
00:37:31It is burned lime. Very good. Okay. How about the second formula? Who can outline the second formula? Everyone should write the second formula.
00:37:52The formula is Ca and we want to turn it into Ca(OH)2. How are we going to do that? How are we going to formulate the second equation?
00:38:05Plus H2O.
00:38:06Yes. Very good. Plus H20- Jan has said it. Okay. Plus H2O. What formula comes out of that? What will be the equation?
00:38:14Ca.
00:38:15What do we come up with? Ca(OH)2- but what else is there. Or no?
00:38:23No, no.
00:38:25Ca(OH)2. Ca, plus-
00:38:29Ca(OH)2-
00:38:32Ca(OH)2. Why don't you, (Dubravska), come up to the board and write it up. Hurry up.
00:38:40You mean the entire formula?
00:38:41Yes.
00:38:46No. Not that. You're supposed to write the second one. Ca, which is lime. Ca plus H2O- as we've said. The result is? Ca(OH)2.
00:39:05But something is still missing there. What is it?
00:39:10Plus H2O.
00:39:12Yes. Plus H2 is still missing. So, what is H2?
00:39:18Hydrogen.
00:39:19Hydrogen. We still need to fill in the formula with?
00:39:242H2O.
00:39:252H2O. Very good. Now let's concentrate on- formula number seven. Let's take a look at it.
00:39:44The number seven formula is CaOH-
00:39:48Number two.
00:39:50Number two and the result is CaCl2. Let's write the formula. Which student- which student will come up to the board and write it?
00:40:07Jakube! Why don't you come over here?
00:40:09Me?
00:40:10Yes, you. Jakube, why don't you write the formula which is on the sheet? CaCl2, CaCl2, draw an arrow- you can probably add something-
00:40:26(inaudible).
00:40:27Wait a minute. That derives from- so the arrow-
00:40:30(inaudible).
00:40:31Yes. Very good.
00:40:33And it's, Ca(OH)2.
00:40:37Number two. Okay. Jakube, I'm going to ask you and the entire class. What is Ca(OH)2?
00:40:46Hydroxide.
00:40:47Hydroxide and what's on the right side?
00:40:49That's... chloride. Chloride.
00:40:53What type?
00:40:54Calcium...
00:40:55Chlo... chloride.
00:40:57Calcium. Very good. Now, why don't you tell me, what exactly is the calcium chloride. What are the substances in the //calcium chloride?
00:41:04//Salt.
00:41:05Salt. Very good. How is salt created?
00:41:08The neutralization of acids and hydroxide-
00:41:10Excellent. The neutralization of hydroxide and acids. So, why don't you write- what kind of acid?
00:41:17HCl.
00:41:18HCl. Very good. HCl. What else evolves out of that?
00:41:31H2O.
00:41:37H2O, yes. H2O. How do we complete the reaction?
00:41:542H2O, yes. Okay? 2H2O, very good. Take a look. I would like to show you this experiment.
00:42:05So, here we have calcium oxide or...
00:42:08//Burned lime.
00:42:09//Burned lime. We put out the lime. What do we use to put it out?
00:42:15Water.
00:42:16Water. What happens then?
00:42:19Slaked lime.
00:42:21Slaked lime or the chemical term is?
00:42:23Calcium hydroxide.
00:42:25Calcium hydroxide. How can we prove, that the calcium hydroxide is present? Does anyone know?
00:42:32Some kind of indicator.
00:42:33An indicator. Do we know of some kind of indicator?
00:42:36The one you're holding.
00:42:37This one here. And what do we call it?
00:42:40(inaudible).
00:42:41No. Can you name some indicators?
00:42:45(inaudible).
00:42:47Litmus.
00:42:48Litmus, very good. Any other indicators? I'm sure you've studied it last year.
00:42:55Phenolphthalein.
00:42:56Phenolphthalein. I have a phenolphthalein in my hand. I'm going to drop some into the liquid. Take a look. It turned-
00:43:05Purple.
00:43:06Purple. I have to- here it is. Can everyone see the color?
00:43:12Yes.
00:43:13Okay? Now, watch please. What do we have to do, in order to produce salt?