Welcome back to the chemistry lesson. So in this lesson we’re going to do somerevision of separating mixtures. Okay so we’re going to work some questionstogether. So let’s start off. The first question we have fill in the blanks. Soquestion A says when crystals of copper sulphate are this sort of in water, the mixture formed is called something. Water is the while coppersulphate is the. So the mixture formed, what is called when we have coppersulphate crystals that are dissolved in water? We have formed a solution. Thenit asks, water is the solvent while copper sulphate is the solution. So we’ve said that the solute dissolves in the solvent to create a solution, B.Solid melts into liquids, while liquids boil to become gas.The temperature at which a solid melts is called, so we have a definition for something,a term or something that when a solid melts, it’s called the, it’s called the melt. point. So when a solid melts it is called the melting point. But when a liquidbecomes a gas, when a liquid boils to become a gas, it is called the boilingpoint. So some mixtures, question C says that some mixtures can be separated byfiltration. Underline which of the mixtures can be separated by filtration.And we have these four. So we have sand and water, we have sand and marble chips, we have alcohol and water,we have sugar and table salt. So filtration. What type of mixture can be separated by filtration?Filtration separates the solid-liquid mixture but the solid to be separated in filtration doesn’tneed to be solid. of alcohol and water I try to put it down the filter paper both of the alcoholand the water would go down to filter paper so I would have nothing. If I havesugar and table salt and I try to put sugar and table salt down the filterpaper both of them again would be stuck in the filter paper and so my mixerwould remain the same. So only sand and water can be separated byfiltration. D. have two water which consists of water and salt. The salts never evaporate, okay? Only the water canbe evaporated and when we boil it the water will turn into water vapor. This can be condensed back,so water can be condensed back and collected as distilled or pure water. So for example,distillation. We’re boiling the water, this is water. and it would go out as water vapor.But if I want to collect the water, the pure water,I condense through a condenser, do water,and I can collect the pure water in a conical flask.So that was question one.Let’s discuss question two.The diagrams below, we have diagram A and diagram B,show the apparatus used to separate

about solid and solid mixtures.And that consists of a solid and a solid,which are mixed together.So we’ve said that we can separate solid-solid mixturesby using a magnet.We can separate by filtration, by chromatography.And today, we’re going to talk about sublimation.So the first thing that we’re going to do in this lessonis to talk about. sublimation. Sublimation is used for solid-solid mixed-chase. So when a fewsubstances, we’ve done what the meaning of sublimation, sublimation is when we havea solid and when it encounters heat it goes directly into a gas phaseand it does not go to a liquid. So when we have a solid directly into a gas that is called sublimation. These type of solids do not have a liquidphase. So for example, this technique of sublimation can be used to separate the components froma mixture which have a solid which is volatile and this one which is non-volatile. So volatilemeans that when heated it would go into a gas and it does sublimation. And when we have a solid which is volatile, which would turn into a gas when heated,and another one which does not turn into a gas when heated.So for example iodine.Iodine is a solid that sublimes, that it turns to a gas directly when heated.So I have a mixture of iodine and sand.And they are in a beaker. How can I separate them?I put this. set up. So I have my bansim bene so that I can heat. I have my gauze or my tripod. I putan evaporating dish or china dish and I do a funnel which is inverted. Now my mixtureis on the china dish or the evaporating dish. So I have my mixture for example iodine andsand which we’re talking about and it would meet a cold surface and as soon as it meets the cold surface it wouldturn a solid again so I have my mixture I heat as soon as I start heating aftersome time the volatile solid which dries in a form of a gas it would touch thefunnel which is inverted and as the funnel is the cold surface it wouldturn back and solid and after all of the volatile liquid has formed here with the funnel thenI have my non-volatile solid which is on the evaporating dish or the china dishand the solid which is on the funnel which is the volatile solid and thatis how we separate solid-solid mixtures when we have one volatile and onenon-volatile mixture. some substances, so we’ve discussed iodine in this case, but other substances that can beseparated by this method are, for example,carbon dioxide, okay, because it’s sublimes, and hydrous iron chloride,aluminum chloride, andsome ammonium compounds, for example, ammonium chloride.Okay, so let’s watch a video together. While I am

Welcome back to the chemistry lesson. So in this lesson we’re going to identifyhow to separate mixed chains in a gas-gas-mixed chain. So by the end ofthis lesson you will be able to identify separating methods of gas-gasmixed chains. So in the last lesson we’ve seen how to separate amixed chains in a gas-gas-mixed chain. solid and the solid mixture by sublimation. So as a quick revision of this sublimationis when we have a solid that when heated turns from a solid and into a liquid sorry and intoa gas it does not turn into a liquid phase and that is called sublimation. Some the sublimationmethod is used when we have a solid which is volatile with when heated goes off as a gas. And the solid, which is non-volatile, which does not go toa gas when heated. And we do this setup over here. Now, for example, if we have iodinesolid and sand solid as well, iodine and sand mixture, solid-solid mixture. So wedo this setup, we put the mixture there, we heat and the iodine since it’s sublines would go off as iodine vapors. As soon asthe iodine would touch the funnel it would go back into a solid state but itwill remain attached with the funnel and like that we would collect the sandwhich will remain in the dish and the iodine which will be as solid on thefunnel and we’ve seen a video of this happening. the last lesson. So we’ve said that there are these, there are a limited number ofsubstances that can use, that can be useful in this method because we needsubstances that can sublime and there are only a few substances that can sublime.Some substances are ammonium chloride for example, carbon dioxide, ammoniumanhydrous iron, trichloride and aluminum chloride and also some ammonium salts. We can use sublimation. Then we’ve seen liquid-liquid mixtures and we’vesaid that in liquid-liquid mixtures we have two types of mixtures. We have the miscibleand we have the immiscible liquid-liquid mixtures. So the miscible, excuse me, the immiscibleliquids are two liquids that you can see line in between them. You can see wherethey separate. For example, when we have oil and water,you can see where is the oil and where is the water.They never mix together.When we have miscible liquids, they are a type of liquidthat there is no layer between themand therefore you cannot see which liquid is whichbecause they mix together.And for this type of solid, of mixtures,liquid-liquid mixtures, we’ve seen that we can separate separating funnel and bifractional distillation. And we’ve seen this, we’ve explained and seenthe videos of this in the last lesson. So in today’s lesson, we’re going to talk aboutgas-gas-mixed chain. So when we have, for example, the error around us, which is composedof a lot of cases, is a mixed chain. So how can we separate one by one? So many mixedchains have start off by liquefaction. What is liquefaction?Liquefaction is the physical conversion of a gas into a liquid.So when we have a gas, such as, I don’t know, water vapor maybe, a simple one,and we turn it into a liquid, what is that process called?When we have water vapor turning into water liquid, that process is called condensation.

Welcome back to the chemistry lesson so we finished off by talking by finishing off separating mixtures topicSo this will be a revision lesson about the topicsoLet’s talk about mixtures and compounds. So we’ve seen what mixtures and compounds areso the main difference between a mixture and attracted to the magnet because the iron still had the properties of the mixturesorry of the element but when iron and sulphur reacts together to create acompound we can see that a new product was formed so a new substance which iscalled iron to sulphide is formed and if I put a magnet next to it nothing willhappen because the compound does not have the properties of the elements and therefore it would bethe compound would have the properties of itself. So new properties with a newcompound would be produced. There we have the reaction for iron and sulphur. We heatup and the iron sulphur compound will be produced. So here we can see thedifferences between a compound and the mixture. So a compound, if we look at a compound first,the composition is always the same.So if I have iron sulfide, FES,the composition would be always the same,one mole reacting with one moleto produce one mole of iron sulfide.However, in a mixture, I can have any proportionas I want.I can have the composition as I want.I can have little sulfur and a lot of iron.I can have a lot of iron and a little sulfur. as I want. Okay, so in a mixture, we can have different varieties of compositions.When we look at a compound, compounds, it is a single substance.It is a new product being formed, but it is only one substance,because we had the iron and sulfur that joined together to produce one compound,a single substance.But when we have a mixture, we can have two or more substances.One… What does this mean?This means that in a mixture, we can have, for example, the air around us.We have oxygen, nitrogen, carbon dioxide, xeon, argon, et cetera, et cetera.And this means that in a mixture, we can have a lot of substances and not only one as ina compound.In a compound, the properties are very different from those to the element, as I’ve saidwith the iron and sulfur. of the new compound are also new for that compound.However, in a mixture, the propertiesare of the individual elements.So each element has the propertiesas it was in the elements.And no new properties are formed for the mixture.The components in a compound can onlybe separated by a chemical reaction.So when we’ve done physical and chemical changesin a compound. we have a chemical change happening, and therefore chemical change can only be separated backby a chemical change, by a chemical reaction. However, in a mixture, we’ve seen a lot ofseparating techniques now. We can separate mixtures differently, but all of theseseparating techniques are by physical means. So we don’t need a chemical changeto separate a mixture. We only need a physical change. Then, the last property for a compound is that a new compound is formed by a chemical change.While in a mixture, no chemical change takes place because there is no new product formed.And then we see how we draw the atoms, how we represent the atoms and compounds.So the atoms are represented just by spheres.Then we have molecules, for example oxygen molecule or hydrogen molecule.

Welcome back to the chemistry lesson. So today we’re going to start another topicWhich is called acid bases and salt and this lesson we’re going to talk about base it sorryWe’re going to talk about acidsSo what is an acid?By the end of this lesson you will be able to define what is an acid you will be able to identify that acidic character can only be seen when in anaqueous solution and you can identify what is as strong and what is as a weak acid.So let’s start off with acids. Most probably you’ve seen thesechemicals in the lab already. So these liquids, they are acids that These are solutions of pure compounds in water, okay?They can be dilute or concentrated.So we don’t understand what dilute and concentrated mean.These acid, if we drop acids or on our skinor on the surface, okay?If they are strong, even if they are weak,but if they are strong mostly, they can hurt us, okay?And they can also tear our clothesor damage the surface that it was poured on. chemical and for acids you will find this symbol for example this symbol thishazard symbol would indicate that the acid if dropped on the skin or on thesurface would damage the surface or your skin okay so we’re here we see here wesee that acids can eat away metals skins and cloths okay so it is verydangerous chemicals I would have they have to be carefully handled Then, we have also some weak acids, okay?For example, a tonoic acid.And it is this acid is found in our foodsbecause a tonoic acid is found in vinegar, okay?So some acids, they are not corrosivesuch as a tonoic acid, cannot be corrosivebecause we use it in our foods.So these are called weak acidswhen they are not corrosive.And for example, a tonoic acid is found in vinegar. that we drink, that is also very acidic.So if you want to do a small experiment at homeand try put the one sense or two sense or five sensewhich is made of copper.And I vary that you put them in a glass of Coca-Cola,they would come out cleanbecause the Coca-Cola is very acidic.Now we have some properties of an acid.So an acid has a sour taste,for example. that we eat, that is acidic as well.And if you taste it, if you buy a lemon, it tastes sour.So acids have a sour taste.They turn blue litmus paper red.So we’ll see what that means.When they react with metals, they produce hydrogen.We’ll see as well what that means.And they dissolve carbonate saltsand they give out carbon dioxide. Also, they are corrosive, as we’ve said.Now, let’s start to talk about what is an acid.So what causes these properties in acids?So acids, when we mention acids, we have a group of chemicals that are called acids.And they are called acids for a reason, because they have something in common.Acids, all of them contains a certain type of iron.And that iron… is the H plus iron, the hydrogen iron. So any type of acid has to have H plus ions,okay? So the H plus ions make acids act as acids. So acids are solutions of purecompounds in water. So for example, if I have hydrogen chloride, HCl, and hydrogenchloride gas, okay? It does not act as a-

welcome back to the chemistry lesson so in this lesson we’re going to continue to talk about acids but in this lesson we’re going to talk about basicity and the properties of acids so by the end of this lesson you will be able to define what basis it is and determine the properties of acids and how they react so let’s do some revision that we’ve done in the last lesson. So we said that acids have H plus ions. So we said that acids have distinct in common and there is some distinct in common is that all of the acids when dissolved in water give H plus ions. In fact here it is highlighted okay because acids are a solution of pure compounds in water. We said that for acidic properties to be seen the acids must be dissolved in water so the H plus ions are when the acid is dissolved in water. So when in water the pure compound the molecular acids break down and form ions and an acid always gives H plus ions. Then we’ve seen this example for hydrochloric acid. For hydrochloric acid, when hydrochloric acid as an acid is not dissolved in water, it doesn’t behave like an acid. But once it has dissolved in water, it will split into ions. Once it has split into these ions, then it will start to behave like acid. And we can see here that HCl would give us H plus ions. and Cl minus ions and therefore since it gives H plus ions hydrogen ions it will behave like an acid. And here we are writing the equation for the dissociation of hydrochloric acid and water. So hydrochloric acid which is aqueous would dissolve in water to give H plus ions hydrogen ions and chlorine ions as we can see in this picture. put, we’re putting HCl, we’re dissolving HCl in water and it will dissociate with H plus and Cl minus. Okay, so we’ve said also that the more hydrogen, hydrogen ions that we have in solution, the more strong is the acid. So the more H plus ions there are in solution, the more acidic it is. And we’ve described strong and weak acids so we can see the distinction in this picture so we said that in a strong acid nearly all acid molecules form ions so when we dissociate such as HCl when we put HCl dissolve it in water it will be a strong acid because all of the HCl will dissociate in water, as we can see in this picture, all of the hydrogen chloride dissolved in water to give H plus ions and Cl minus ions. However, in weak acid, only some of the acid molecules form ions, so not all of the molecules form ions and therefore we have few H plus in weak acids, as you can see in this picture. ethanoic acid, for example. So you have the molecules here which are not separated, which were not separated in water, okay? Which did not dissociate in water. However, we have only one molecule that dissociated in water. And therefore, since only one molecule from the rest dissociated in water, few atoms dissociated in water, we can say that it is a weak acid. So a weak acid always has a lower pH than a strong acid. And we will discuss pH meters in more detail in the next lessons. But you can see that the 7 is neutral, like the water that we drink. Then we have the acids which go underneath 7. So the weak acids are somewhere here, between 3 and 6.

Welcome back to the chemistry lesson. So in this lesson, we’re going to talk aboutalkalies and their reactions. So we’re going to talk about the reaction of alkalies.So by the end of this lesson, you will be able to understandthebases and how they react. You will be able to understand the reaction of alkalies with ammonium salts understand why calcium oxide and calcium hydroxide are used to neutralize soiland you will learn the term neutralization. So let’s do some revision first. So in thelast lesson we’ve discussed the properties of acids and the properties ofalkali. So the properties of acids for the first property is that acids have taste. Obviously we cannot taste acids in the lab so do not try it but if you tastea lemon lemon is acidic and you can taste that it has a sour taste right but if wego to the alkalis they have the opposite they have a better taste obviouslyalkalis we cannot taste them. They also have a soapy feeling so alkalis and have a soapy feeling. How do we know the soapy feeling that alkalis have?This is because soap has alkalis in it and therefore we know that they have a soapy feeling.Also, we’ve discussed indicators in the last lesson. So acids turn blue litmus paper red.So if we dip a blue litmus paper in acid, it will give red and that will show usin the soapy feeling. solution that we have is an acid. Alkalies on the other hand turn redlitmus paper blue. What if, what if I dip blue litmus in alkali? What do you thinkwill happen? If I dip blue litmus in alkali the blue litmus would not changeand would stay the same. The same happens if I dip a red litmus in anacid. If I have a red litmus litmus paper and they dip it in an acid it will stay red. The disadvantage that litmuspaper has is that from a litmus paper you only know if it is an acid or analkali because you cannot know the pH of a solution. Only the universal indicatorshows if it’s a strong or weak acid or it’s a strong or weak alkali. Now, as we’re talking about strong and weak, we have acids which have a pH number lessthan 7.So between 6 and 0 are the acids.On the other hand, the alkalis have a pH between 8 and 14.The 14 shows the strongest alkaline while the 8 is the weakest alkaline.On the other hand, 6 is the weakest acid while 0 is the strongest acid. then we have electricity.So, when we conduct electricity, as we’ve said, we need ions.If we don’t have ions in solution, we cannot conduct electricity.So, when we have a lot of ions in solution, so we have a strong acid,we have a bulb that would light up bright.However, if we have few ions in solution,we have a…

welcome back to the chemistry lesson so in this lesson we’re going to continue to talk about acids and we’re going to continue to talk about acid reactions so by the end of this lesson you will be able to identify general trends of the products that produced from the following reactions and appreciate some limitations of these reactions. So let’s do some revision of the previous lesson. So in the previous lesson, we’ve talked about basisity. What is basisity? So basisity, we said that acids produce H plus ions when in an aqueous solution. So when acids dissolve in water, they give, the acids dissociate and gives H plus ions in solution. So, basicity is the number of H plus ions, so the number of hydrogen ions, which I produced per molecule and that is called basicity. So, basicity is the number of hydrogen ions that I produced per molecule of acid. So, for example, we Hydrochloric acid, hydrochloric acid formula is HCl. So HCl is H and the chlorine. So when it dissociates in water, it would dissociate in H plus and the chlorine minus. When the molecule dissociates in water to give only one H plus ion, it is called mono basic. More or no, because it gives only one hydrogen ion in solution. What about sulfuric acid? Sulfuric acid is H2SO4 from the previous lesson. How many hydrogen ions do you think sulfuric acid can give us? Sulfuric acid can dissociate in water to give two H-plus ions and sulfate. So since sulfuric acid has 2H in the chemical formula, it can give 2H+, it can give 2 hydrogen ions. And therefore we do not call sulfuric acid as monobasic. We can say that it is dibasic because sulfuric acid can give 2 hydrogen ions per sulfuric acid molecule. What about phosphoric acid? Phosphoric acid has a chemical equation of H3PO4. So, from the chemical equation and from your previous knowledge, what can phosphoric acid give us? Phosphoric acid would dissociate in 3H+, and phosphase ions. And therefore, it is neither monobasic. It is not dibasic, and it is called tribasic, because phosphoric acid… gives 3H-plus perimolecule. Then we have nitric acid, which we discussed some reactions in the previous lesson. Nitric acid is mono-basic, and therefore, we say that it gives H-plus ions. It gives only one H-plus ion perimolecule. Now, then we discussed these reactions. We had reaction of magnesium, zinc. zinc and iron with hydrochloric acid and with sulphuric acid. So we’ve seen that magnesium reacts with dilute hydrochloric acid and sulphuric acid the same. So magnesium gives, when we have a magnesium ribbon put in hydrochloric acid, it would show a free essence, rapid free essence, and it would form hydrogen. This is also seen. in sulfuric acid, and it also gives hydrogen in sulfuric acid. The remaining solution, both of the acids, is colorless. So after the reaction, the solution that remains is colorless. And we write the chemical equations. So magnesium with hydrochloric acid would be magnesium chloride and hydrogen. Magnesium with sulfuric acid gives hydrogen.

welcome back in the chemistry lesson today we’re going to continue to talk about acids bases and salt but in this lesson we’re going to talk about alkali now in the previous lessons we’ve seen what is an acid but now we’re going to start talking about what is an alkali so by the end of this lesson you will be able to define And we have some examples. For example, we have magnesium reacting with the lute sulphuric acid to give magnesium sulfate and hydrogen. How can we test for hydrogen? Yes, we can test for hydrogen by putting a lighted splint at the tip of the test tube and it would burn with a pull. So, in this reaction we can see that the material is displacing hydrogen to get the salt then the hydrogen is get driven off as a gas now when we have acids with base acids with base they would give a salt and water so as we’ve said bases are compounds that react with acid to give only salt and water we can have metal oxides and we can have metal hydroxides so for example copper oxide and for example sodium hydroxide. Now for example we have these reactions here so we have hydrochloric acid with sodium hydroxide which is a base and we would get sodium chloride as the salt and water. Then we have another example with so with here we had with metal hydroxide then we have another example with metal oxide so we have sulfuric acid which obviously is the acid then we have the copper oxide and this gives the copper would displace the hydrogen and this gives copper sulphate and water we’ve also seen in the previous lesson acids with carbonate. Acids with carbonate would give a salt and water but they would give an extra product that extra product is carbon dioxide. So for example if we have calcium carbonate with hydrochloric acid it would give the salt which is calcium chloride, water and carbon dioxide. Then we’ve seen another reaction which is not mentioned here. The other reaction is metal, sorry is acid with sulphides. Acid with sulphides would give us salt and water with an extra product of sulphur dioxide. Let’s talk about alkali’s. What are alkali’s? So we’ve seen that acids dissociate in water to give H plus ions but alkali’s are given other type of iron. When dissolving water, alkali’s produce OH minus ions. So when we have a substance that is dissolving in water to give OH minus ions can say that it is an alkali. For example, we have sodium hydroxide which dissociates in water to give Na plus iron and OH minus iron. Since we have the OH minus iron, we can say that it is an alkali. So if we look at this diagram, we have the sodium hydroxide and we are dissolving it in water. The sodium hydroxide will dissociate in the sodium ion and the hydroxide ion, okay? So it will dissociate in hydroxide ion and sodium ion. Once we see that hydroxide ions are being produced when dissolved in water, we can say that this substance is an alkaline. However, for example, we have ammonia now, it dissociates a bit different, but it still gives us a little bit less.

Welcome back to the chemistry lesson.So in this lesson, we’re going to talk about alkalis and the properties of acids.So we will also talk about what are indicators.So by the end of this lesson, you will be able to identify common alkalis,you will identify the characteristics of alkalis and acids,and you will… also know what indicators are used for. So let’s do some revision about the lastlesson. So we said that we have alkalis and we have bases. So we distinguishbetween a base and an alkali. A base we said is a metallic oxide or hydroxidethat reacts with an acid and we’ve seen that metal oxides such as copper the softened water, because an alkali is a soluble, when the softened water it woulddissociate to give OH-. And we have some examples here such as sodium hydroxide,magnesium hydroxide, etc. And we have this diagram to help us out. So we have baseswhich is big in the middle because all of the alkalis are bases. Bases are or hydroxides of metals. As, for example, copper oxide or sodium hydroxide. Then bases can be classifiedinto insoluble bases and soluble bases. The soluble bases are called alkalis. While the insolublebases, they are classified just as base. Then we’ve discussed strong and weak alkali. We saidthat the alkalis is a soluble base with dissociates in waterto give OH minus ions.And we’ve seen an example for sodium hydroxide.Sodium hydroxide, for example this,dissociates in water to give sodium and hydroxide ions.When sodium hydroxide, you have the diagramthat can help us understand.When sodium hydroxide dissolves in water, give it fully dissociates to give sodium and hydroxide ions. Since it sodiumhydroxide fully dissociates to give sodium and hydroxide ions, that sodiumhydroxide is considered as a strong alkali. And therefore this means that themore OH- ions that we have in solution, the more alkaline is a solution. But whenwe look ammonia. Ammonia is a bit different than sodium hydroxide. Ammonia, which isconsidered as NH3, when reacted with water it gives ammonium and hydroxideions. It is an alkali still because it gives hydroxide ions. However, most ofthe ammonia will not dissociate in water and only a few hydroxide ions. will be given in solution and therefore ammonia can be considered as a weak alkali.Ammonia dissociates differently than sodium hydroxide because ammonia has covalent bondingwhile sodium hydroxide has ionic bonding and therefore only few ammonia molecules formions because we’ve seen in the previous lessons that covalent bonding normally do not dissolve in water. However, ionic compounds dissolve in water, such as sodium hydroxide.Now let’s look at some properties of alkalis. So we have alkalis that can have SOP feeling.What does this mean? When you feel alkalis, obviously we cannot touch alkalis in a labbecause they can be corrosive.