LAST MIN IGCSE CHEMISTRY PAPER 6 ATP REVISION | Planning, Seperation Techniques, Tips and More!!!

Added: 2026-05-13

[00:00:00]Hello guys and welcome back to one more IGCSE chemistry paper 6 video. So if you haven't seen I highly urge you guys to watch the previous last year's paper 6 video. This is um sort of an extension to that. It covers some other points and if that video or this video does help you please like and subscribe to this channel. It really helps the channel get going. And let's start. So we'll start with the planning question first and then we'll cover this exam question from the uh latest paper which is from the October November 2025. Um okay. Now um when solving planning question you should know the apparatus that's needed to answer that question. You should also review common chemistry techniques for example rusting electroplating and electrolysis. You should know them because you can be asked to set up an experiment for this, right? And sometimes you can be asked to find the formula, right? Which is percentage composition by mass. That means you have to find the mass of um for example, if you have an impure substance. Let's say this is calcium carbonate solid and it has some impurities. So percentage composition would be um the amount of calcium carbonate in grams divided by the whole um the gram or the mass of the whole substance. Now um what are the steps to do such kind of planning questions? You should identify the method and the apparatus. What is the technique that you're using? What are the steps that you're going to follow?

[00:01:23]And what is the paradise that you're going to need? What is the method for that? You have to think logically. For example, if you're in a science lab, how are you going to do that experiment?

[00:01:33]Electroplating, how is the setup? What are some uh steps that you should take?

[00:01:36]Any safety precaution? Whatever. But you know, just think logically. And then any control variables how to and how are you going to what's the apparatus how are you going to measure the variables that you need and um the other variables the control variables would be at constant you can even say use known concentration or volume and then when you're repeating that when you're repeating the experiment uh use the same amount of the same concentration or volume. Okay. And then after you're done with the experiment to improve accuracy, repeat three times, take the average and then to in order to analyze results, you have to um maybe find out the formula. Maybe observe the change to notice something.

[00:02:14]Okay, so let's start with this question.

[00:02:17]When a solid metal is added to an aquis salt of a less reactive metal, a reaction takes place. Okay, so you have um a container of a less reactive metal.

[00:02:29]It is a liquid. It's aquous, right? So the salt is dissolved in water. Okay.

[00:02:33]Sometimes you can even be asked to define what is aquis. Aquis salt is basically a salt which is dissolved in waters. Okay. So that can be an um one more question maybe and then you're adding a solid metal into this and a reaction occurs. Okay.

[00:02:50]The reaction is exothermic. That means the heat energy is given out to the surrounding and the temperature of the reaction mixture increases obviously. So you might need a thermometer. The larger the difference in the reactivity of two metals between uh this metal and the metal that's dissolved here, the more exothermic the reaction. That means the greater the change in temperature.

[00:03:10]Cobalt, manganese, nickel are three metals which are all more reactive than copper and react with aquis copper sulfate. All right, so we just found out that this is the aquis copper sulfate solution and you're going to be adding these metals. The temperature of the reaction mixture increases during each reaction. plan an investigation to find the order of reactivity of the three metals um cobalt, manganese, and nickel.

[00:03:36]Your plan should include how you can use the results in order to find the order of reactivity of the three metals.

[00:03:42]Right? So, the general idea is that you're going to have um a beaker or a container and you're going to add a known volume of copper sulfate and then you're going to keep a thermometer inside and measure the initial temperature. add the first solid which might be cobalt and then observe the increase in temperature for let's say after for some time okay for a period of time and then repeat the same experiment for manganesees and uh nickel now we can also talk about some control variables or some ways to increase accuracy control variables use the same concentration and same volume of copper sulfate use the same mass of solid that you're adding these are the steps you're going to add a known volume of copper proper sulfate solution using a bureid into a beaker. Why are we using a bureid? Because that is going to increase the accuracy of the volume measured. Okay, you could have even used a measuring cylinder, but beard is more accurate. And then um using a thermometer, dip that thermometer in in the beaker and measure the initial temperature of this copper sulfate solution. And then you're going to carefully add a known mass of cobalt into the beaker. Now, this is a planning question, but let's say it was some other kind of question. And they would ask you why do you have to add this carefully? Let's say this is your um beaker. Okay. And you're adding uh you just throw it inside. Okay. And then if you just throw it inside and let's say this was full to the top, you will have some splashes, right? So some copper sulfate might splash out and that is going to reduce the volume and you might get wrong results. For example, if you're measuring the volume or something like that, after the reaction, let's say, or you know, whatever the question is, it's going to reduce the accuracy.

[00:05:22]And then you're going to measure the highest temperature reached. You um you're going to repeat the same repeat the experiment with same mass of other two metals and the same concentration of copper sulfate. The highest increase in temperature is for the most reactive metal. So some other questions that could have been asked if this was um a normal question would be how to improve the accuracy of this. Now you are measuring the change in temperature, right? So instead of using a normal beaker, you could use a plastic cup instead of let's say if you're taking the thermometer out to measure that's um that might change the temperature. So keep the thermometer inside. So make sure you're measuring the most accurate uh temperature. The answer is given here for you to double check. Let's move on to this. Now, apparatus is very important. It's the most probably the easiest way to collect marks in paper six. So, let's try to um answer these questions on the way. A is thermometer.

[00:06:20]Now, you can obviously this is a fractional distillation experiment. You should know this experiment as well. Um we'll label this and we'll then go through the experiment. B is the beaker.

[00:06:31]D is the condenser.

[00:06:34]This is fractionating column C is going to be this is a tripod stand.

[00:06:44]You should also be able to identify that you have heat under that. So it could be some flame by one simmer but mention heat. Okay, that's enough. So now this is useful for fractional distillation right when you have a mixture of liquids that could be separated because they have different boiling points. Now let's say if we have um ethanol and water uh mixture. Okay, water boils at 100° and ethanol boils at around I guess 80°C. Okay, now you could do that. But the thing is ethanol is a flammable material, right? So you could be asked this question. Why is it not a good idea to use um open flame for example with the Benson burner when you have this mixture? This is because ethanol is flammable, right? So you have to use an electric heater in that case. Okay. So now let's say if you have another mixture of um two other or three other multiple liquids that are here, how will you do it? So you're basically going to set up an experiment like this. You'll keep your mixture of liquids here and then you're going to heat it. Now you have let's say two substances. Substance A boils at 60°C, substance B at 70 and uh C at 80. Okay. So, you're going to heat this. When it reaches 60°C, A is going to boil and it's going to raise the fractionating column and it's going to reach the condenser. At the condenser, it's going to um because there's cool water coming in. This is going to cool down the the evaporated gas and it's going to turn back into a liquid and it's going to fall here.

[00:08:19]Right. After that, all of that has um reached here, you're going to remove the beaker and bring in another beaker. And then you're going to increase the heat until the the until this reaches 70°C.

[00:08:32]You're going to separate it, change the beaker, and then increase the heat until it reaches 80°C. And then um you will be you will separate these three liquids really easily. These are some other experimental setups. So um this is a conical flask.

[00:08:51]A is a funnel. I think it's a thistle funnel. And then C is an inverted measuring cylinder.

[00:09:00]So this can be used to measure the volume of gas.

[00:09:10]And then over here you can say this is the Bunson burner because that's used to heat up that limestone.

[00:09:19]And then that's a retort stand.

[00:09:22]Over here you have um a dropper that is used to drop some water on this lime.

[00:09:29]Okay. Okay. Now here you have three different paradise measure volume. First one is um a pipet.

[00:09:39]Second one is a bureet and the third one is a measuring cylinder. The thing is three of these substances are used to measure volumes of of liquids but they have their own advantages and disadvantages. Okay, remember measuring cylinder has less accuracy whereas borage has more accuracy and pippet has the most accuracy.

[00:10:07]Disadvantage is that pippet can only measure one volume. Okay. So for example, if this is a 25 cm cube pipet, it can only measure one volume whereas you know with um borit you can measure a range of volumes and here as well. Now um one disadvantage of bureid and pipet is that it's kind of slower to um use compared to a measuring cylinder. You can just pour it quickly. So it can be done very quickly. So this is used for example in titration when you need more accuracy and measuring cler is simply when you want to pour for example in um some liquid in a beaker and you want like rough rough volume you don't want high accuracy that's when you can use a measuring cylinder.

[00:10:51]So some more uh this is the measuring cylinder we do know that this is a tripod stand and this is a spatula.

[00:11:02]This is a glass rod. This is um a mortar and pestl. And this is a filter funnel.

[00:11:08]This is the filtrate. What's going to filter out is a filtrate.

[00:11:14]So you also have a filter paper right here. Chromatography. This is how the chromatography setup looks like. You have a beaker and then you have a glass rod on which the chromatography paper is hanging. So you dip this chromatography paper in a solvent. And the key thing to note about this solvent is that this solvent has to be soluble in your sample. You keep your sample here. If the solvent is not soluble in the sample, these would not separate. Okay.

[00:11:42]So, one thing to note is this. Another thing to note is that this is the baseline which is drawn with pencil.

[00:11:49]This is where you keep your you keep your samples like this.

[00:11:55]One question that you can be asked is which equipment is used to uh draw the baseline. You will say pencil for the solvent. Remember solvent is supposed to be soluble in sample. It should touch the chromatography paper.

[00:12:10]Remember chromatographic paper is also known as the chromatog. Chromatography is a process to separate substances and it can also provide us information to help identify them. Why? Because they have specific RF value. Now, what are what are your steps? First of all, you have to take your sample and crush it.

[00:12:28]If it's a solid, you have to crush it.

[00:12:30]For example, if you have some grass, you take some grass. You using a mortar and a pestl, you're going to And then you will, if it's a liquid, uh you don't have to do that. And place your uh sample on this baseline.

[00:12:44]Now, uh and then uh dip your chromatography paper into the solvent. A very important point to note is that your baseline should not uh should be above the solvent. So it doesn't dissolve. Okay? And then you will lose your sample. So you leave this set up for some time. After some time these sample these travel up they travel to different heights based on their solubilities. Okay. More more distance traveled. If there is a greater solubility of sample in the solvent, the solvent travels up the paper by the capillary action. Now using this you can calculate the RF value. What is RF value? RF value is specific for every substance. So based on the RF value you can identify which substance was in the sample. So after some time you might see something like this. You have to calculate RF value for each of these individual dots. So the RF value is distance traveled by the substance divided by distance traveled by the solvent. So for example, if this was uh 20 and this was 40 cm going to be 20 / 40 equals to 0.5 no unit because this is cm this is centimeter they cancel so there's no units. We have something else as well which is called as a locating agent. A locating agent is used when your sample is invisible. You cannot see the chromatography that has occurred. So you will uh spray the the locating agent on the chromatograph. And the locating agent is going to make the invisible substances visible. It can either make the invisible substances visible or it will flourish under UV light. When you put UV light, it will shine. Now this is another um diagram of chromatography, but there are three mistakes. Can you identify the three mistakes?

[00:14:37]All right. So the first mistake is that the samples that we have they are not on the baseline. They are below the baseline. And why is that important?

[00:14:46]Because how will we calculate the RF value? If we don't know the starting point, how will we know that what is our distance traveled? Another mistake is that you can see these three samples, they're not on the same height. If their starting point is different, their final point is going to be different and it will not again have an accurate RF value. And finally, the last mistake is that if you can see the solvent is not even touching the chromatography paper.

[00:15:14][snorts] If that if it's not even touching, the chromatography won't even occur.

[00:15:20]All right. Now, we have another example of chromatography. Can you conclude three points from this uh from this experiment?

[00:15:28]Okay. So uh let's look at the first one.

[00:15:31]The first one has only one uh spot. This shows that this was a pure substance. It was only made up of one substance. Now the second one, you can see that this did not even move from the from the baseline. This mean it was not soluble in the solvent. Now we cannot identify anything about it. For the third sample, we can see that it was made up of two uh substances. Another thing you can notice is that this one this this pot and this pot are the same height. This means both of them have the same RF value and they're both same substances.

[00:16:08]Now we can move on to another process called as crystallization. So we use crystallization when we want to obtain the the solute from the solvent. For example, if you have a solution a salt solution. If you want to obtain the salt from a salt and water, how do we do it?

[00:16:22]The first step is you're supposed to so you have your solution, right? You put your solution in this evaporating basin and on a put it on a tripod stand and then put a Bunson burner underneath it.

[00:16:33]So you are supposed to heat your solution.

[00:16:37]Then uh when you're heating it, first of all, some water or some solvent will evaporate making it more concentrated.

[00:16:43]After some time uh you you have to keep heating it until it reaches the point of crystallization. What is the point of crystallization? That is where the crystals start to form. In questions like these, you can be asked a lot of one mark questions. So, it's important that you know them. You should know the the labeling of the diagram. You should know what is happening in each of each of these uh steps and why is it happening. All right? So, for when you reach point of crystallization, you're supposed to remove the heat and we're leaving it to cool.

[00:17:14]And then uh when you when you leave it to cool, the crystals start to form as you can see here. And in the next step you will do filtration. The crystals will be filtered out is as a residue and the filtrate it will pass through the filter paper. Now one more question that you can be asked is why are you doing filtration to separate this the crystals from the solvent. After this you're supposed to wash your residue to remove any droplets of filter. For example if it was an acid or some other chemical you want to remove any traces of that filterate you have to wash the residue.

[00:17:46]After washing the residue, you have to dry it with an absorbent or filter paper.

[00:17:53]Now, one more important concept that you should know is titration. Titration is uh when you mix two solutions. The most common example is perhaps when you mix acid and base. So, it can be used to determine the concentration of either of them either the acid or the base. You can notice how much acid how much volume of acid is needed to neutralize the alkalion. can also be used to prepare salts because acid plus base is salt and water. Now what is the process? You keep a conical flask. Okay. And then you use a a volumetric pipet. You use a pippet when you need to add a known volume in um in a flask. So here we need to add 25 cm cube accurately. That's why we use this volumetric pipet. We use a filler.

[00:18:36]This helps to pour it down. The next step is you're supposed to add an indicator. What is an indicator? An indicator is used to identify the presence or absence of something and it tells us whether it's acidic or basic something like that. So uh some common examples are phenoline. Phenolin is colorless when it's an acidic solution and in alkali solution it turns pink.

[00:18:59]Another common example is methile orange. This is also very useful for titration examples. In acid it's red and in alkali it turns yellow. In nutrient solution it's orange. Okay, in neutral solutions uh for phenolin that's also colorless in neutral solutions. Now if you have a lipmus paper remember this limus paper is not ideal for titration because how are you going to dip it while you're doing titration? In acidic solution it turns from blue to red. So you have to use um a blue lmus paper it will turn red and for alkala you have to use a red lmus paper and this turns blue. Now what do you do? So after you add your acid uh sulfuric acid and indicator in the conical flask first um you keep a white tile on the stand and then you put your flask and then you will fill your bureete with the alkali.

[00:19:47]So here we have calcium hydroxide. Open this bure allow the alkalide to to come in drop by drop. Make sure that you are constantly swirling it so that it mixes.

[00:19:57]Now whenever the acid and base have neutralized each other it will change color. If you have added phenolin it's going to turn pink. Now what are some points to notice here? We don't you uh use universal indicator. Why not?

[00:20:11]Because universal indicator changes colors so many times from very acidic to acidic to neutral. So it's very hard to know the end point. End point is where one drop like one more drop of the base is going to cause a sharp change. For example, here we can easily identify and then we can measure the volume on the bureet. Now how we're supposed to remove air bubbles from bureid before starting the experiment. How do we do that? Like this. And we have an empty beaker. We run the bureid so that if there are any air bubbles, it will uh it will be gone.

[00:20:44]Now uh you are supposed to repeat until you get a consistent volumes. You can draw a table. Then so this is how your table could look like. You'll have the initial volume from the bureet and then write down the final volume and then uh subtract both of them final minus initial to find the volume used. Now what is the volume used? It's 20. This is just a random number. Now it's uh sometimes you can just continue the experiment. Final volume will now become the initial volume and then you will open the bure until it changes color.

[00:21:17]Let's say maybe this was 20. What is the volume used? It's 20. Now you can have 20 here. But make sure after every experiment you are supposed to change the the conical flask with a fresh flask. Wash your conical flask again.

[00:21:31]Add 25 cm cube of your acid add indicator and keep it there. But you can have the same period. Now you can see so we're getting consistent results and know we have some accurate results. Now we can move on to some general um chemistry paper. Six points. Whenever you're reading experiments like these always read from the lower miniscus.

[00:21:49]Okay. So this is going to be 46.1. This is not 46. Take care of that. Let's say if this was mercury. Mercury has um an upper meniscus something like this.

[00:22:00]Okay. So you have to read here the upper miniscus which would be 45.5. So take care of that. You will face a lot of questions where you have to find the change in bure reading maybe the volume of substance that reacted. So you just have to subtract this number from this number final minus initial and then you might be asked to plot a graph. So when you're plotting a graph here, they gave you the numbers for the x-axis but not for the y- axis, right? So choose a scale that allows you to make a graph that covers at least more than half of the graph. Okay? If it's less than half, that's not a good idea. Use a pencil.

[00:22:36]Also, when you're plotting, make sure your line goes straight through the points. Don't include anomalous points like that. For example, if you had like a point over here, no need to include that because that is, you know, sort of that's wrong. So you could be asked some reasons why maybe the experiment was not done correctly. For this uh point I'm going to cover some points how you can improve the accuracy of your paper six experiments. Okay. So let's say if you're asked if you're given an analog um apparatus analog stop clock or thermometer. So the obvious um accuracy would be to use a digital stock clock.

[00:23:14]Okay. In uh if asked if you're given a measuring cylinder, the accuracy would be to use a bureet. Even more would be to use a pippet.

[00:23:24]And then for example, change in temperature is measured use and they're using a metal cup without a lid. You have you can use a poly strain or a plastic cup that because that is not going to conduct heat and you're not going to lose that heat in the surrounding. And cover it with a lid. If your thermometer is inside, keep it inside. and then obviously repeat and average for um for best results. But you cannot uh repeat an average if the question asks you to change the apparatus. Okay, so the question says what change in apparatus would change accuracy. Don't mention this point obviously. And then um let's say a question says why have they crushed lumps of carbon carbonate? Why the why would they crush it into powder for reaction? We have crushed it into powder because that is going to increase the rate of reaction. And how? Because the surface area has increased.

[00:24:14]There's more exposed surface area for copper carbonate to react with whatever it is reacting with. Now let's say we have an experiment like this and um this is your salt for example and this is the substance or acid this is going to react with. Why would they keep this set up?

[00:24:29]This is a thread and it is holding your or your solid. This is because there's going to be no gas escape as you're not going to remove the bunk. You're just going to tip this flask and this liquid would um come in contact with the with the solid and the reaction would occur, right? You don't have to remove the bunk. So there's no escape of gases and that's going to increase the accuracy of your experiment. So if we have this these graphs and we are supposed to identify which one is exo and endothermic, we can know that endothermic is this one. Why? Because endothermic takes in in energy.

[00:25:01]Potential energy inside it will increase. Remember endothermic takes in energy. So in the surrounding the temperature will become um cooler. Now it's taking in the heat. On the other hand, this is the exothermic reaction.

[00:25:16]Potential energy of the substances will reduce and it will release heat outside.

[00:25:22]This is exothermic. Exothermic uh reaction will increase the temperature of the surrounding. These represent the activation energy. Now moving on here we have three types of graphs. Now, so on the first graph, this nine had a steeper graph compared to this one. So this means if we're talking about surface area, this one has a greater surface area. Uh the substance is more exposed to react with the other substance, more successful correlations. That's why there's going to be a greater rate of reaction. As you can see with the steeper graph, however, the volume will be same. On the other hand, if the concentration is different, volume is not going to be the same. in the final volume. Why? Because remember concentration means mole per unit volume. There is a greater number of moles that that are going to react per unit volume. So you will have more reaction. Finally, if you have a difference in temperatures. Now more temperature means more kinetic energy successful collisions a greater rate of reaction. You can see the graph is steeper. However, this again volume will be same. Sometimes you will you will be asked to draw two lines like this. For example, make sure that you label that this one is experiment one, the other one is experiment two. Sometimes you will even need to extend the line to 0 0. Everything is going to be mentioned in the question. So make sure that you spend your time and uh understand the question properly. Then sometimes you will even have to extrapolate like this to find the common point and identify the time maybe or whatever that is. Now for test of gases, same test and qualitative analysis. This is given in the end of your paper six but make sure that uh you read it now so that you will be prepared in the exam. Remember to read what these are. Ammonia turns red to paper to blue because when mixed with water like it says here that is damp it it becomes alkaline or milky. Now another name for lime water is calcium hydroxide. Chlorine bleaches a damp litmus paper. Remember it's supposed to be damp. For example, if they ask you if if it was dry, will it work? No, it has to be damp from for a flame test. These are your metal ions, the cations, and these are the flame colors. You uh there's a there was a question in the exam which said, "How can you do flame test?" You need a blue bunil burner flame. The a blue flame is non- luminous. Next, dip your unreactive metal wire into the substance and then expose this metal wire on the flame. I have made a video about this. You can check it in the description. If it was orange, red, it means that some irons were present. Next, for qualitative analysis, again, these are given, but it's a good idea to go through them at home and practice as many questions as you can.

[00:28:07]Um, some things that you can remember is that if you see berium, it it's for sulfate. If you see nitrate, silver nitrate here, silver nitrate, this shows that they're testing for a halid. If they're testing for carbon dioxide gas, it means there is a carbonate present.

[00:28:24]Remember all sulfates except berium and calcium are soluble there. That is why when you see when you have sulfate, we form sulfate berium. This is a white precipitate. All nitrates are soluble.

[00:28:35]That's why we don't have a peripate with nitrate. We have a gas. And then all chlorides except lead and silver are soluble. You can see in chlorides we're using silver nitrate and we get a white peripate.

[00:28:47]So that is all about IGCSC chemistry paper 6. If you have any more questions, do let me know.