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Science Education Focus
"Peace, mercy and blessings of God be upon you. How are you guys doing? I hope you are all well."
"Thank God we're finished. God willing, we'll see you in another session."
This video effectively combines educational content with motivational elements, making it a valuable resource for students aspiring to excel in science and pursue further studies in STEM fields. The approach taken by the presenter highlights the importance of understanding foundational concepts in chemistry, which is critical for success in any scientific endeavor.
Peace, mercy and blessings of God be upon you. How are you guys doing? I hope you are all well. This is Mohamed El-Hader from Sadat City, and today is our second science session at Sadat City. Let's begin. The first thing we will start with is the periodic table. We all know that this periodic table includes the elements that have been discovered since the beginning of what elements are, up to the present day. The one who made this periodic table was the scientist Mendeleev, and he arranged the elements according to atomic weight. After him came the scientist Moseley, who modified the periodic table and found that the elements actually acquire their properties according to the atomic number, not the atomic weight. Therefore, the elements are arranged according to their atomic number. That is why, if we notice, iodine, even though it is less than trillium in atomic weight, is next to it. Why? Because it has a higher atomic number, meaning a higher number of protons. When they divided the periodic table, they divided it into four categories: the S category, this category, the B category, and the S category. The S category includes two groups. The first group, which is this, is called the alkali metals. The second group, which is this, is called the alkaline earth metals. Okay, let's look at this category, which is in the middle. This whole category, what are they called? They are called metals. They are called transition elements. Okay, let's look at the next one. Let's look at this group. Let's look at these few, which are in green. What are these few in green called? Post-transition elements or weak metals. Let's look at the ones in light brown. These elements are called metalloids. Let's look at the ones in blue. What are they called? The nonmetals... Now let's move on to the noble gases. They're called noble gases, and you need to memorize them. What does that mean? You need to memorize them because there are many questions about them. Say them with me: Helium, Neon, Argon, Krypton, Xenon, Rhodon, Ogazone. Okay, let's move on to the last two. The first row is called Lansides. What's Lansinides called? The second row is called Actinides. And that's it, I think. We've finished everything in the periodic table. Next, we move on to the chemical reaction series, which you should memorize almost as well as your own name because there are many questions about it in chemical equations. Focus on it. Say them: Potassium, Sodium, Barium, Calcium, Magnesium, Aluminum, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Mercury, Silver, Platinum, Gold. Now let's move on to the first question: What is the smallest particle of matter? We all know that the smallest particle of matter is... Now, someone might ask me why I'm talking about the atom, specifically the electron or nucleus. They might ask why I'm using the electron or nucleus, arguing that these are smaller than the atom. But I've already explained that the electron and nucleus are part of the atom. The nucleus represents the energy level, and electrons orbit within it. If you combine several electrons, they won't make matter, and similarly, several nuclei won't create matter. However, if you combine several atoms, they will form matter. A molecule is composed of more than one atom. Therefore, the correct answer is the atom. Now, let's look at some more information about the atom. The atom is the smallest particle, the smallest building block of matter. All matter is made up of a group of atoms. The components of an atom are positively charged protons, neutrally charged neutrons, and negatively charged electrons. The components of the nucleus are protons and neutrons, while the electrons outside the nucleus orbit it. An energy level is the electrons, and every element in the periodic table has a unique type and number of atoms. For example, if I told you that an element with atomic number 11 is known to be sodium, and then I told you that this number increased to 12, would it still be sodium? No, now the element has completely changed. Now it's magnesium. So, every element has its own atomic number. Okay? And this atom comes from a Greek word called 'atomos'. Okay? What does 'atomos' mean? It means indivisible. And you can't see the atom with the naked eye; you have to see it with an electron microscope. And that, I think, is everything about the atom. So, let's solve the questions. The second question asks which of the following is found inside the nucleus of the atom. It gives you one: protons, two: neutrons, three: electrons. I just said above that the atom contains the nucleus and electrons. What does the nucleus contain? Protons and neutrons. So, the correct answer is only one and two. Okay? Which of the following does not have a positive charge? We know that the one with a positive charge was the proton. The proton is the one that had a positive charge. So, we will choose an option that does not contain a proton. What is the only option that We have no protons, only electrons and neutrons. Electrons are negatively charged and neutrons are neutral. Okay, let's move on to the next question. It asks you, in the diagram shown in front of you, what is the atomic number, mass number, and number of neutrons, respectively? Now, here's an important point: what is the atomic number and what is the mass number? The atomic number is the number of protons inside the nucleus. So, the nucleus is the number of positive protons inside it. This is called the atomic number. Okay, while the mass number is the sum of the protons and neutrons inside the nucleus. Okay, and the atomic number equals the number of protons equals the number of electrons, but why in a neutral atom? Because if an atom were to enter an ion, or be involved in a chemical reaction, it would lose or gain electrons depending on its state— metal or nonmetal. Therefore, if the atom is neutral, meaning in its neutral state, the atomic number will equal the number of protons equals the number of electrons. But if it's not in its neutral state, we can't say that. The third thing I want you to know about the atomic number is that it's the basis for arranging the elements in the modern periodic table. As I mentioned earlier, the scientist Masley rearranged the elements based on their atomic number because he discovered that elements acquire their properties from their atomic number, not their atomic weight. And as I said, it's what determines the identity of the element. So, the 1 in atomic number is the symbol for the atomic number of NA. But if we make it 12, we completely change it to MG. So, that's what I want you to know about the atomic number and the mass number, which is the total number of protons and neutrons inside the nucleus. Okay, and this is a very, very important piece of information: the atomic number, or mass number, I mean, does not equal the mass. Why, sir? Because we all know that the mass number is the sum of the protons and neutrons, we completely forgot about electrons. Wait a minute, guys, we completely forgot about electrons! Even though electrons, yes, their weight, size, or mass is very small, they do have mass, so we have to consider them. And we have a very important rule that you need to know: the number of neutrons equals the mass number minus the atomic number. Okay, that's the rule we'll use to solve this problem. So here it tells you that you have, in order, the atomic number, the mass number, and the number of neutrons. We know that the atomic number will be 1 and the mass number will be 23. The atomic number is on the bottom and the mass number is on the top. Now we want to know the number of neutrons. We subtract the mass number from half the atomic number, which gives us 12. So therefore, the answer will be the atomic number 11, the mass number 23, and the number of neutrons The answer to the question " What is the answer to the question about 12 neutrons?" is correct. Now, let's move on to the next question: An atom of an element has 12 protons and 1 neutron. What could its atomic number and mass number be? We just said that the atomic number is the number of protons, so the atomic number is 12. We also said that the mass number is the sum of the protons and neutrons. Therefore, the mass number would be 12 + 12, which equals 24. So, the correct answer is... Now, let's move on to the next question: Which of the following elements is considered a metallic element? Here, we come to an important concept: metallic and non-metallic elements. We all know that non-metallic elements are characterized by a metallic profile, good conductivity of heat, good conductivity of electricity, and so on. But this question doesn't focus on all of that. It focuses on what the outermost energy level of a metal is: one, two, or three. A non-metal's outermost energy level is either... Five, six, or seven—that's the point he's focusing on here. So, if we start distributing what he's given us, we'll find that we'll begin with the first element, which is 1k. You might say, "But it's the last one; it should be a metal." Well, no, this is the biggest trap you could fall into. You might think it's hydrogen, and we all know hydrogen is a nonmetal. That's why he gave it as the first option, to trick you, even though it's the last one. It's not a metal; it's a nonmetal. Okay, let's distribute the next one. We'll find lmn. This will be in 2, 8, 8, 2, 8, 10, 8, 12, 2, 8, 10, and 8, 18. What's left at the end? What's ne to make 20? Here, at the end, we find that nene has an ane, and we said that metals end with either 1 or an ane. Therefore, the correct choice is b. Okay, let's move on to the next question. It asks you to imagine that the world is facing a major problem. To solve this problem, a specific chemical reaction is needed. Which of the following elements can be used? We mentioned the inert and noble gases above, and we heard them. We said that inert gases have very low reactivity because their energy level is already full. They do n't participate in chemical reactions under normal conditions. When we heard them, we said they are helium, neon, argen, krypton, xenon, and radon. So, the answer would be xenon. But if you notice, all the other elements can participate in chemical reactions without any problem. Now, let's move on to the next question. It asks you to choose four elements with atomic numbers 8, 11, 15, and 16. Yes, 16 is the correct answer. They are below each other, meaning they are in the same group. Since they are in the same group, the outermost energy level has the same number of electrons. However, if they are in the same period, they have the same number of energy levels, but the number of electrons in the outermost energy level changes as they move from one group to another. So, first, we'll distribute these elements. First, we'll distribute element 8. Okay, here it is: KLM 6. Now, let's move on to the next element: element 1, KLM 2, 8, 1. Next, element 15, KLM 2, 8, 5. And finally, element 16, KLM 2, 8, 6. As we said, since they are in the same group, the number of electrons in the outermost energy level will be the same. If we look at the element that has the number of electrons in the outermost energy level, we'll see the number of electrons in the outermost energy level. Six, six, and here too, the number of electrons in the outermost energy level is six. Therefore, we conclude that the correct answer will be 8 and 16, which is C, which is C. Okay, let's move on to the next question: Which of the following classifications of elements is correct? Here, he's dividing them based on what? Metal and non-metal. If we look at the first ones: potassium, fluorine, and lithium. We know that potassium is a metal, fluorine is a non-metal, and lithium is a metal. So, from the beginning, this is wrong. Let's move on to the next ones: lithium, sodium, potassium, and the second one is chlorofluorine. We all know that lithium, potassium, and sodium are all metals, and these are all non-metals. Therefore, this is the correct answer, which is answer B. Let's move on to the next question: When moving from cesium to sodium in the periodic table, does the atomic size decrease, increase, decrease, increase, or not change? This one will lead us to the question: What is atomic size? And what is it, I mean its specifications, like atomic size, this means the size of the atom, what is the size of the atom? The larger the size of your atom, the more energy levels it contains. Okay, so here it tells you that if we move from sodium to estizium to sodium, we all know estizium is at the end and sodium is above. Here in the group, I will tell you something, that in the group and here in the course, in the group, as you go down, the atomic size increases, and in the course, as you go up, the atomic size decreases. Okay, you will ask me why, as you go up in the course, the atomic size decreases even though it is supposed to increase, because you are increasing the number of electrons. I will tell you here, as the number of electrons increases, then consequently the force of attraction of the protons to it will be greater. Why? Because it means that if you have tweezers here and tweezers there, they will attract each other, just like if there were five here and five here. If there were five here and five here, you'd find them pulling each other right away. But if there were one here and one there, they might not attract each other at all. You might ask me now, "When you go down, the group also gets bigger." I'll tell you that every time you go down, you increase an energy level, and this is a known fact. So, as long as you're increasing an energy level, you're increasing the volume. He's telling you that if we move from cesium to sodium—meaning, if we go up— what will happen if we move from cesium to sodium? If we go up, then the atomic volume will decrease, contrary to what we wrote here, which is that when you go down, it increases. He's telling you that when you go up, it decreases. Okay, let's move on to the next question. He asks you which of the following elements has the greatest tendency. Electronic. The first thing we need to understand is what electron mileage actually means. Electron mileage is the amount of energy released when an element gains an atom of electrons. You might say you still don't understand what that means. I'll simply tell you that an element with a high electron mileage gains more electrons and releases a lot of energy when this happens. It's worth noting that the element with the highest electron mileage is chlorine, and chlorine has an atomic number of 17, so the answer will be 17. I think the question is easy. Now, let's move on to question 12: A chemical element has three electrons in its principal energy level. What is its position in the periodic table? Since it has three electrons in its principal energy level, and the principal energy level of hm is hm, we'll do this: the nucleus is hm, and we'll put 2, 8, 3. And here's what it tells you? We know that a period is the number of energy levels, while a group is the number of electrons in the last energy level. So how many energy levels do we have? 1, a, 3. So it will be in the third period. So we eliminate a and eliminate c. And here it has how many electrons in the outermost energy level ? So, we will eliminate B, and the correct answer will be D, I think. The question is easy. Let's move on to the next question: In which category of the periodic table do the atmospheres of metals fall? We said above that the S contains what are alkali metals and alkaline earth metals, and the D contains what are the transition elements. We came to the F and said it contains lansanides and actinides. We came to the B because it is diverse. We found in it first the weak metals and some transition elements, and then after that the metalloids, and then after that we found the nonmetals, and then after that we found the noble gases and inert gases. So, where do the metalloids come from? You come in the group, in the category, let's move on to the next question. It asks you, in the image in front of you, what is the name of the group and what is its valence? Here, it gives you the information that the Y group has an atomic number of 11. So when we divide it, when we, I mean, when we distribute it, we find that the nucleus is 2, 8, 1. We find that the outermost energy level has one electron. Since there is one electron, then this is Group 1A. And since it is Group A, its valence is one. When it participates in chemical equations or reactions, it loses only one electron, so its valence is one. So the correct answer is Group 1A, and its valence is one. Which of the following elements can give a positive ion? The one responsible for giving a positive ion is the metal. We know that helium... we all know that helium... One of the inert gases that doesn't participate in reactions at all, so we exclude chlorine, which we all know is a non-metal, so we exclude fluorine, the same applies, it's a non- metal. Therefore, the correct answer is NA, a positive ion. This is what, when you distribute it, gives you a positive ion. Let's try to do it. First, NA in the neutral state will be like this: 281281. We will convert it to an ion, we will put 2, close the bracket, and put it here plus one, so it becomes positive one because it has lost an electron and a positive one has been put in its place. Therefore, the only thing that forms a positive ion when it participates in a chemical reaction is what? Metals. Now, let's move on to the next question, which asks how many elements are in the compound N1N3. We will count them like this: first sodium, then sodium, then nitrogen, then oxygen. So how many elements are there? I think this is one of the questions that came up. Let's move on to the next question. It asks you about the conversion of sodium to a phi ion. Which of the following is incorrect? When we convert sodium to an ion, we just converted it up there. We converted sodium to an ion. It asks you which of the following is incorrect: The number of protons is greater than the number of electrons. We all know the number of protons doesn't change. Okay, when we enter the reaction or when we convert to an ion, so the number of protons will be 11 and the number of electrons in the ion will be 10. So this is correct, not wrong. Focus, it says it's incorrect, so this statement is correct: The number of occupied energy levels decreases. Here, there were three before, now there are two, so this is also correct. The mass number decreases. We said that protons and neutrons have nothing to do with the reaction that will occur; electrons are what enter the reaction. So the mass number will remain the same. What is it? This is the wrong sentence. This is the incorrect sentence. The number of electrons decreases. Yes, here the number of electrons was 11 and here it was 10, so this sentence is correct. Here the only sentence that is incorrect is: The number of books decreases. Okay, guys, let's move on to the next question. Question number 18 asks you about the type of chemical bond present in the H2 molecule. This question has a nice twist. It asks you about the type of bond present in the molecule. You'll automatically say, "I mean a single covalent bond." Okay, why? Because when you draw water, you usually draw HH. But if the question asks you about the bond between water molecules—it doesn't say "between," meaning within the water molecule—it asks you about the bond between the molecules themselves. If it asks you about the bond between the molecules, you'll draw a molecule, and you'll find that the bond between them is a hydrogen bond, not a single covalent bond. So focus on this point. This is strong because it is important. If he tells you that in a molecule of H2O it will be a single covalent bond, but if he tells you that between molecules it will be a hydrogen bond, let's move on to the next question. Question number 19 tells you that when two atoms of an element are bonded together, the element is in group 6A, so the type of bond formed is... Here, the two atoms are in group 6A, and what do they both want to do ? They want to fill their outermost energy level, so this one will share, and this one will share two, and this one will share two. When this one shares two, then this one will have a total of 1. And when this one also shares two, then this one will have a total of 8. So, since this one shared two and this one shared two, then the bond here will be a double covalent bond. Focus on these questions, they are easy, and these are the ones that should earn you marks. So, let's look at question number 20. It says that an ion that carries two charges has an atomic number of its atoms. It carries two charges. Here, let's draw each one. When it transforms into an ion, 17, when it transforms into an ion, will be like this: 28. And it will close. This will be negative one, but okay. Since there is negative one here, then if we decrease one, there will be negative two. Okay, since if we decrease one, there will be negative two, then the correct answer is 10. I mean, C. Which is 16, but let's distribute the rest so you don't get stressed. We'll distribute the two, and it will be like this when it turns into an ion, and there won't be anything here because we know that these two are gases, inert or noble gases, which is helium. We'll distribute the 10 again, and we won't find the same thing either. We'll add a German one here, which is neon. So what will the correct answer be ? So, 16 will be fine. Now, let's move on to the next question: Which of the following represents the ion of an element? The ion of an element is Mg-241. It tells you that it represents its ion. When we draw the Mg ion, we'll first do what we've done. Here, up here, there's an empty space. Here's Mg. Okay, when we draw its ion, we 've drawn its ion. We all know that the number of protons and neutrons doesn't participate in the reaction, so the number of protons, which is 12, will remain constant. So, we'll eliminate a and b. Okay, and we just said above that the number of neutrons equals the mass number minus the atomic number, 24. Na = 12, which gives us 12. Okay, we're stuck between this and that. Now, let's look up because the number of electrons is 10. Because the number of electrons decreased since Mg is a metal, and since the question asked, the number of electrons will be 10, not 12. This answer is also ruled out, so the correct answer is S. Let's move on to the next question. Question 22 asks you if the order of the elements according to chemical activity is ABCD, where A is more chemically active than B, B is more chemically active than C, C is more chemically active than D, and D is more chemically active than D. It then asks which of the following reactions is impossible. Which of these reactions is truly impossible? Let's start with the first reaction. The first reaction tells you that A will give ISO4+A. We know that A has a higher activity than A, so it can replace it, and that's correct. Next, C and D. C has a higher activity than D, so it can replace D, and that's also correct. Now, D wants to replace B. But here I'll stop. B is more active than D, so D cannot replace B; it will stop there. Therefore, this answer is the one that is truly impossible. It's impossible. So the answer is C. Okay, let's move on to the next question. It asks if an element in group 6 of the modern periodic table gains two electrons. The element that causes this is in group 6. We know that as long as an element is in group 6, it's a non-essential element. And as long as an element is non- essential, it will gain electrons. Since it will gain electrons, we need something else to lose electrons so that it can give them what it lost. So, we need something that is in group 6. Therefore, we will eliminate this answer and this answer along with it because it has a third element. We will then have group 3 and group 2. If you notice, its valence is triple, meaning it loses three electrons, while group 3 has a divalent valence, meaning it loses two electrons. And we already know that it has electrons, so the correct answer will be B. Okay, let's move on to the next question. 24 asks what the moment of the world is that Arrange the elements in ascending order according to their atomic weights. We said that the one who arranged them according to atomic weight was Mendeleev, and the one who modified the arrangement to be according to atomic numbers was Moseley. So the correct answer is C. These scientists' questions are general. Either you know the scientist and say it, or you don't know. There's no guesswork involved. Let's remind you once of the scientists you learned about in the first year of middle school. I hope I haven't forgotten anything. First, we start with the scientist Mendeleev. He is the one who developed the modern periodic table based on atomic weight. After him came Moseley, who modified the periodic table and arranged it based on atomic number because he found that elements acquire their properties according to atomic number, not atomic weight. After him came the scientist Rutherford, who made the first nuclear model of the atom and discovered the protons. After him came Bohr, who discovered the energy levels, and how many were there ? Seven, then we come to Dalton, who discovered the atomic theory, that matter is composed of indivisible atoms. Next, we come to Newton, who discovered the laws of motion and gravity. Then we come to Einstein, who discovered the theory of relativity, which describes the relationship between energy and mass. Next, we come to Thomas Edison, who invented the light bulb, and also Mendel, who taught us the laws of heredity in the third year of middle school. Then there's Robert Hooke, who first observed the cell under a microscope, and then Charles Richter, who developed the Richter scale, which measures the intensity of earthquakes. After that, we come to Watson and Crick, who were the first to develop the double helix model of DNA. So, I think that's all the scientists you have. If I forgot anything, leave it in the comments. And then we come to question 25, which asks which scientist discovered the protons. We just said that the scientist who... The one who discovered the protons was Maine Krasner Ford. He discovered the protons and created the nuclear atom model. The next question is: 26. The scientist who discovered the principal energy levels, who was this scientist? We all said it was Bohr. We just said that Bohr discovered the principal energy levels and there are seven. Now we come to the next question: Which of the following options correctly describes the location and characteristics of the transition elements in the periodic table? We said where the transition elements were located in the periodic table? In this group, and this group is located in the middle, the only one that is actually in the middle is this one. It is located in the middle of the periodic table and has electrons in this group that are not filled. Therefore, the correct answer is: Now, let's look at question 28. Which of the following elements belongs to the alkali earth group? We said that the alkali earth group was what group? 2. We said the first one was called the alkali metals, and the second one is the alkaline earth metals, which is the alkaline earth group. So, we will distribute all these elements. First, we will distribute X: 11, X is 2, 8, 1. So, it is in group 1, i.e., not aniine. Therefore, this is impossible. Now, let's distribute some of the 18 elements. We will find that the 18 have the same distribution, but this one will be 8. So, it is in group 0, not in group 2. Therefore, this is impossible. Now, let's distribute the 20 elements. When we distribute the 20 elements, we will add aniine here as well. So, this is the one that In Group 2, the answer is C. Okay, let's move on to the next question. Why are noble gases considered the least reactive elements in the periodic table? We all know that noble gases have a full outer energy level, and we know that elements become reactive to fill their outermost energy level. So, the outermost energy level is already filled. Therefore, the correct answer is that the outer energy levels are completely filled with electrons; they don't need to fill anything else. It's already a full energy level, so what more can you do? That's why they only become reactive under certain conditions. Question 30: Which of the following is a chemical reaction? A piece of wax melts. Water evaporates when heated. An iron nail rusts after being left in water. A bottle breaks into pieces. Look, a small chemical reaction requires something new to emerge; it can't be the same as before, otherwise it's called a chemical reaction. Take wax; it's a piece of wax, and when you melt it, it will still be almost the same. Similarly, when water evaporates, it turns into water vapor, but if it evaporates, it will remain water. Breaking glass is still glass, just a small piece. But a nail... a nail is made of iron, which is iron oxide. When we leave it in water and expose it to oxygen, it transforms into a layer called Fe₂O₃, which is iron oxide. So, this is the correct answer: the iron nail after being left in water. Now, let's move on to the next question, number 31. This question is based on the periodic table. This shows the number of periods: 1, 2, 3. This shows the periods: 4, 5, 1. This shows the groups: 1, 2, 3. 4, 5, 1, so it tells you that silicon, which is like this, SI 14, 28, tells you which of these symbols it belongs to: ABCD. Let's distribute it, we won't boil it. When we distribute it, it will be 2, 8, 4, 1, 8, 1, 4. So if we put it in the place of one of the existing symbols, it has how many periods: 1, 2, 1, 2, 1, 3, so it will be here, okay? And it has V, V, 4, 1, V, so it will be in group 4, 1, 2, 1, 2, 3, so the correct answer is B. Its place will be here, SI will be here, so the answer will be B. Now let's move on to the next question: Which of the following reactions is a reaction of the current state? Now we've entered into reactions and this nonsense stuff. Let's explain it to you simply. First, the types of chemical reactions. First, why does the atom, why does the element resort to entering into chemical activity, as I said before? This is so that it completes its last energy level in order to reach the stages where it is satiated and does not want anything more. Chemical reactions are of several types. The first type is the substitution reaction. The first type is the combination reaction. A reaction called the combination reaction. What is the combination reaction? This is two compounds, meaning two elements that combine to form a compound, and its general formula is a plus b. Let's take an example of it: the formation of water. The easiest example is hydrogen plus oxygen. What does that give us? Water. This is the first reaction we have. Okay, let's erase this. The second reaction we have is the decomposition reaction, and it has several types, but generally, we will take it in a general formula. What is the decomposition reaction? What is a decomposition reaction? The compound IB that we made can be reconstituted as I + B, and so on. The most famous example of this is the electrolysis of water. 2H2O will give us 2H2 + O2 by electrolysis. Now, there are the thermal decomposition reactions that we have all been studying. Now, let's move on to the next type. Just a second, let's move on to the next type, which is simple displacement reactions. Simple displacement reactions, what are they? They are based on the principle of chemical activity. Element A enters the compound PC, takes the place of the element and removes it, resulting in the compound AC + B. The most famous example of this is the example of ZnZn + 2HSL, which will give us ZnSL2 + H2. Now, let's move on to another type of reaction, double displacement reactions. Just a second, let's move on to double displacement reactions. What happens in these double displacement reactions? It involves an exchange between two complex ions to produce two new compounds. What is its general formula? A plus CD gives us AD plus CB. An example of this is N ASL plus EG3 gives us N3 plus EGSL. This will be a white precipitate. Okay guys, let's move on to the next type, which is combustion reactions that occur in the presence of oxygen. What are combustion reactions? Combustion reactions are those where there's oxygen and a spark. Once there's a spark and oxygen, the reaction is complete. If you're burning an organic material, you'll get CO2 and O2. For example, if we put CH4 with oxygen, we'll get CO2 and O2. But when we balance the equation, we'll find that there's an a and a two, so we add two, and the equation will be balanced. I think that covers all the types of reactions you know. Now let's solve the problems. It asks which of the following is a thermal decomposition reaction. We're still on thermal decomposition, which is something that breaks down and returns to its original state or simpler compounds. The only thermal decomposition here is CO3, which gives CO. So, CO + CO. Okay, guys, let's move on to the next question: Which of the following is a simple displacement reaction? A simple displacement reaction is when an element becomes higher than The chemical element replaces the hydrogen in its compound. The answer that matches what I said is number B: Zn replaces H in its salt solution, resulting in Zd₂O₄ + H₂. Now, let's move on to the next question: Which of the following is a double displacement reaction? A double displacement reaction, where both ions exchange, is the same example we mentioned: ICl + IGN₃ gives N₃ + IGCCl. This reaction, my friends, is called a double displacement reaction because IGCCl is a white precipitate that doesn't dissolve in water. Next, the question asks which of the following elements reacts with water the fastest. Since it reacts with water the fastest, it has a greater ability to displace hydrogen and replace it. Therefore, it will be the most chemically active element, which is potassium. Let's review the sources of chemical activity: potassium, sodium, barium, calcium, magnesium, aluminum, zinc, iron, tin, and lead. Hydrogen, copper, mercury, silver, platinum, gold. You absolutely must memorize these like your own name because they will be incredibly useful, even in exams. For example, if you encounter a problem, you might be able to solve it. Honestly, I used to solve it using these methods. Now, let's move on to the next question: Which of these represents the concentration of reactants and products during a chemical reaction? Look, we learned in middle school that as the reaction progresses, the concentration of reactants decreases, and conversely, as the reaction progresses, the concentration of reactants and products increases. So, at the very beginning, the concentration of reactants is 100% and the concentration of products is 0%. Then, at the end, the concentration of products is 100% and the concentration of reactants is 0%. Therefore, during a chemical reaction, what happens is that the concentration of reactants decreases and the concentration of products decreases. That's the answer. Okay, everyone, let's move on to the next question: Which of the following three reactions is expected to occur most rapidly? To answer this question more quickly, the answer might be a bit long, but seriously, the question is good. The general answer will be A. Why? Because any ionized solutions in water can easily react as soon as the two solutions are mixed. That's why it says ionic reactions in aqueous solutions are very fast because the movement of molecules and electrons is easy, and they collide quickly. This collision is what actually causes the reaction. Okay, you might ask why not B or C, or that's the mistake in B. When hydrogen and oxygen gases form water, the reaction is slow under normal conditions because it requires heat or a liquid. The gas reaction, in general, depends on the collision of molecules, and it's less efficient because the molecules in the air—you know, gas molecules move randomly, not in a regular motion—so the percentage of them colliding with each other is low. Therefore, the reaction will decrease. Let's move on to number C because C, C, and O need a very high temperature to combine to form O2 for complete combustion. Solid materials like carbon react slowly because of the limited surface area in which it reacts with oxygen. The last one is sugar with acid. Heating reactions require heating and a high concentration of acid and take a long time to complete. In addition, organic reactions in general are complex and occur in stages, so the fastest reaction will be 1000. Okay, let's move on to question number 38. What is the name given to reactions in which a catalyst is added to increase their speed? We all know these are positive catalytic reactions. Number 39: The graph opposite, any curve representing the general reactants and products, is the catalyst, respectively. In this question, we said at the beginning that the concentration of the reactants is 100%. What here has a 100% concentration? C and D. If you notice, the concentration is 100%, and the concentration is... The products are 0%. What here has a 0% concentration? It's reactant A. It's the only one with a 0% concentration. The catalyst is unaffected throughout the reaction. So, the answer would be that the reactants are C and D, the products are A, and the catalyst is... (This is the answer to question number 40). A student conducted two experiments to accelerate the breakdown of starch into sugar. In the first, he added a catalyst, and in the second, he added human saliva. After a few minutes, he noticed that the breakdown was faster in the second experiment. What is the scientific explanation for this? The scientific explanation is that human saliva contains a substance called amylase. It's an enzyme that accelerates chemical reactions, specifically the digestion of starch and sugar. That's why, if you notice, after eating starch, you feel it has a sugar content because this breakdown happens quickly. You understand. Therefore, the correct answer is that saliva contains an enzyme that acts as a catalyst... The reaction speed without being consumed, because we already know that the catalyst isn't consumed throughout the entire reaction period. So, it's introduced to accelerate the next reaction. They mention heat in the experiment; yes, heat will have a factor, but its effect isn't significant. It's not directly involved in the reaction itself; it will increase the speed. Saliva is acidic, but not acidic enough to cause dissociation. The sugar produced from dissolution caused an increase that wasn't actually related. So, the goal is to achieve that. And that's it, guys. Thank God we're finished. God willing, we'll see you in another session. Peace out, guys. Peace. Salam.
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