This lecture provides a clear and systematic foundation in chemistry, effectively simplifying complex quantitative concepts for early-stage learners. It is a well-structured entry point that prioritizes conceptual clarity for competitive exam preparation.
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Arjuna NEET in English 2027 First Chemistry Class 🚀 Start Your NEET Journey | Gaurav Singh Arora SirAdded:
Good evening. Good evening. Good evening everybody.
Good evening. Yes. So we are live. Good evening everybody. Hello and welcome to PWJ PW need English channel. My dear Arjunas. My dear Arjunas, Peta from today. Hello. Hello BJP for Rajasthan.
Hello Ana, I remember this name. I guess you are coming from for those rene sessions as well. Ana, then we have Torox. Then we have Inaya. Beautiful name. Then we have Maya, Sulena, Cutie.
And then we have Aran Shri. So good evening. Good evening. Good evening everybody. Now uh sir your introduction in Hindi BJP for Rajasthan.
Beta as you can see from the uh channel name beta we have to be compassionate enough. We every every every each each one of practically knows that we live in India and yes we our national language is Hindi but beta why compassion because there are many students and many area of society where Hindi is not a first their mother language and because of that are don't don't those students also deserve to be served with the best possible content yes they they deserve that all the equal opportunities beta And because of that uh we have this separate funnel for English and that's why we are compelled to only speak in hind in in English although I'm quite uh capable of speaking Hindi also Punjabi also but uh the reason we are here a to communicate the complete J and neat level content in English and two to have an environment where all the serious students can join in. Why I'm saying serious? I know you each and every one of you are serious.
But beta even we have observed this those English funnels they are super crowded with all the spams that the the serious doubts all the students who are serious enough and they are joining on a platform because obviously it is quite economical. Uh but they do not connect with their exact questions with the teachers and therefore to create a separate funnel for all the serious crowd. uh the that is the second uh reason for this separate English funnel.
Now, huh? So, it I know I know beta each and every one of you is serious. The only reason is because of few distractions. Some some I mean I will not say every but yes some students get distracted during the journey. Now let us start the uh the class. This is the first class for Arjuna neat in English and obviously I'll be starting with the I'll be your chemistry educator during this journey. I'm my name is Gorav Singhura. I've completed my BTE uh from NIT groupetra long back in the year 2011 I completed uh and yes since that time I have been teaching mostly in an offline funnel but yes thanks to BW I guess uh with previous one one and a half year I have been uh giving my services in the online sector as well. Although although I am telling you as an educator once you go in an offline class beta the teacher do not have to prepare that well once we come in an online platform whatever questions whatever theory we have we we are planning to teach in a class we have to do the complete homework no matter how much confidence or how much experience we have beta we have to work and that's why even I feel even even that is the feeling which I have right now and it has also taken 1.5 years to get that that feeling that why we are getting optimum results in an online platform. So if you are serious enough now what I am not going to discuss any timetable for you because I definitely know you have just cleared your class 10th examination and cl before your class 10th board examination every mentor used to tell you that you should not study the whole night and I know 95% of you have studied that the the the night before your examination and you have scored wonders you have scored wonders with your examination and after giving that examination you must have came back to your place and thought sir if I can study so much in one night wonders I will do if I will be maintaining this place throughout the throughout the year and that's why I know I definitely know you have that intent in you that you can do anything and I am telling you that white coat that beautiful and honorable white coat is waiting for you but in order to in order to wear it with pride the very first thing you need is start now I'm not saying you join Arjuna neat in English you join anywhere but you start right now because what happens is sir is uh whatever you have studied in class 10 the whole complete year syllabus will be done in a in a month I'm not saying 11th is difficult beta I'm not saying need it is difficult but yes it is it requires discipline discipline of what whatever your teacher will be teaching each day you have to make sure that you will be religiously completing the class notes on that particular day. Point one. Point two, attempt the related DPSPs. Point three, if that that topic for you is requiring more questions for practice, then you should practice more questions around it. We you should definitely have those PW modules or if you do not have then for all the serious candidates I'm telling you either go for a proper reference and beta those references also will have limited questions. So rather go for the infinity batch. It is just a top up of I guess 1,100 rupees because anyway for physics, chemistry, bot, zoologology, you will be buying those references. The those four three four references will anyhow make around 1,500.
Uh so I this is just an advice beta because you need to practice but the practice will be built on the foundation and the foundation is completing each and every lecture on the same day. This is point number one. Now, now point number two. Point number two is whenever you are dealing with with a single day's lecture beta in any day, you will not be asked to make build a Taj Mahel on the same day. What becomes difficult for student is that they do not recall the formula there that they must have read 10 days back. So what to do? Whenever I am delivering these lecture notes, most of the students has very sound handwriting so that they can connect with the teacher also. they can listen to the concept also and they can write also particularly if you'll ask me I still remember in 11 12th I was just in my own district and I didn't even prepare for J because I was an MP board student and uh yes we didn't have that much of of of informations around but yes after 12th I thought n I want to if I will be doing engineering I want to do with in an IIT or an NIT then I took a drop I still remember I've gone to uh I I have no problem in saying that because they are my teachers. I have gone to resonance.
I've learned physics through RKV sir. I have learned chemistry through SPR sir but I I learned organic chemistry through Vijay Pratima Mittal VP madam and they all are legends. I completely agree. But SPR sir used to teach in organic chemistry and I mean he used to divide the board into four halves. He used to say everything and he used to write that thing and when he he used to move over here then I used to write that thing. Why? because my writing speed was very slow. So what I'm telling you what I am teaching over here is not your concept. It will become your concept when you will completely copy what I'm writing. No, first if your writing speed is sound enough then okay maintain the pace but if not then after every class during the live class first connect with the teacher after that once you are having because you will definitely be having minimum two classes per day because you are class 11 students you have no backlogs.
Complete the live lecture with the teacher and after the lecture is done post your dinner just spend the another one hour or maybe two hours for two classes and then prepare your notes by yourself not by completely copying what I'm written over here but by writing what you feel that you have been communicated from my side through my lecture notes also and through the recordings also. So beta it will create such an impact inside your head that each and every formula will be recalled inside your brain cells in a zify while giving your examination because 180 minutes 180 questions requires requires requires full and full concentration and absorption of your class notes in your head. How they are going to be absorbed once you are going to revise those class notes each and every day. Sir once after the class you are preparing your notes you are obviously revising you are obviously re reading it again and while reading it again I am telling you and after after every Sunday you will again be revising the complete complete uh week portion weeks labels that you have done. Now let me tell you third last and final third thing.
I have been teaching since 2012. So I have seen series of students coming and passing by. that in the initial 1 month or maybe 1.5 month every student performs to the maximum efficiency and you know what happens as you as I already communicated each day work will be a piece of cake that you will feel our mentors used to say class 11th was very difficult it is halua it is a piece of cake for me then you start missing one day work two day work thinking in mind I'll be completing it on the Sunday on that Sunday you will be having more pressure why because the the the work that you that has been kept pending. Maybe on a Monday the the concept that are thrown to you requires more pro practice but you do not have clarity of the previous three or four class lectures then you will skip that chapter or you will not have that confidence in that chapter and these things start building up when they start building up you will again plan on a Sunday that I'll be completing everything and then the pressure starts building and because of the anxiety that is silently created in the brain cells your efficiency dips take anything and once backlogs start happening beta they are fungus they keep on growing inside your emotions your your I mean you will not try to have those backlogs but they will they will pop up coming and how to avoid them first start from the beginning start your preparation from today as we have already started Arjuna neat in English so this is one option for you but even if you are planning not to join but still join anywhere but start from today. I hope I have made myself clear. So again good afternoon, good evening everybody. Mr. Perfect, SN Biswas, then we have Aran, then we have Manish, Chri, then we have Ratana sir please. Uh okay. So your wish is my command. Yours Sam I am starting and uh the lecture that we have discussed and planned to start is basic concepts of chemistry. The mole concept sir what will be our task for today? Our task for today will be we'll be discussing the basics that you have learned in class 9th and 10. But yes we'll not be spending much time but yes we'll be brushing upon all those basic concepts.
What are those classification of matter?
And then we'll be directly jumping to mole concept. Why? Because this is the first class and because it is coming live in YT obviously once you'll be meet once we'll be meeting regularly in the batches we'll be making the pace quite slow quite relaxed because we have time but today because this is the first class so I'll not be wasting time in those law of chemical combinations because obviously they are there you must read them but they are least important. No, none of the question has came from them in the previous years.
Practically zero questions and uh therefore we will be focusing on the on the most important area which is introduction of mole concept and let's see let's see if in the first class only maybe we can make some J mains and need questions. So move with that intention let us move to what is matter. I hope you know this from class 9th and 10th.
What is matter? So all of you in the comment section can you please reply what is a matter sir? What is this? We all know that matter is anything that has mass and occupies space. But practically whole of this universe is made of what? That the manifested world that we have is basically divided into two parts. The first part is a matter which anything that has mass and occupies space and the remaining part is energy. So energy h and matter has constituted your practically complete manifested universe. Now if you know this that matter is anything that has mass and occupies space. Now give me a practical answer first. Beta I have a picture over here of a candle which is burning which is lighten lightened up. So this lightened candle has two parts. This is the solid candle and this is the flame that it is creating. First you answer me what answer to me that what this candle is.
It is a matter or energy.
What is it? This candle is matter or energy. This candle is matter or energy.
I want everybody to answer in the I I'm not giving you any poll for today because obviously those polls yes no everything we have in our live batches but no poll for today because I want to maximize the discussion for today. So come on tell me what uh the candle that you have is a matter or energy. Come on.
Ah yes yes definitely everybody's right.
Everybody's right.
This is a matter.
This is a matter. Why sir? Because it this this wax has definitely mass and it occupy a volume. We know we can see that matter. Definitely correct. Now you tell me this flame this flame is a matter or energy. This flame this flame is matter or energy. The flame that that creates the illumination inside your room that flame is a matter or energy.
Wax is matter. Flame is energy. Amit is saying then uh bod is saying it is energy. Okay. Flame is energy. Flame is energy. Flame is energy. Flame is energy. Everybody is incorrect. Flame is also a matter.
Eh hey sir you said hey sir you said anything that has mass and occupies space is matter flame is a matter that means we have either you are telling us wrong or we have read the wrong definition beta that is the beauty of science now it the the actual science has started your ninth and 10th mentors must be telling you that keep on asking question now I'm asking you question. How you are seeing that flame? You are seeing that flame because com combustion of unburnt carbon because combustion of atmospheric gases because combustion of those dust particles those gaseous components are taking place. You know why you see that flame? Because the combustion what is combustion? It's a reaction with oxygen.
So who is reacting with oxygen and creating that combustion? Some some in unburned carbon and some gaseous particles are undergoing reaction with oxygen. Sir those molecules are made of atoms and atom is the basic constituent of matter. That means the flame that you are seeing you are you are only seeing it because ma because there is chemical reaction. What is combustion reaction of oxygen is taking place with somebody that somebody are molecules. So that molecules undergoing reaction is making that illumination.
So that means this flame is definitely also a matter.
Then sir we should need a practical definition. Now those bookish definitions is not going to help you for your practical. So let us start studying science practically. I will give you a definition of matter. A practical definition of matter. Now let me first give you that practical definition of matter. What you know sir we know anything that has mass and occupies space is matter. But now sir practically we are modulating practically we are modulating what is a matter. So anything now the definition the practical definition yes many many will say sir this is uh uh because in your class 11th and 12th you are not supposed to give the definition of matter. That was till class 10th. Now you just have to know so sir how you have written the definition by observing and examining all the possible options that are thrown at you by J obviously we are being exam focused so how I am defining matter for you so that it can give you a practical definition also so anything [clears throat] if you can see it if you can see that thing it's a matter you can see that flame no that's it that means it's a matter so if you can see it it's a matter but but that converse is not true always. That means if you if some if something is matter then you can definitely you can see it. No, because air is also a matter. Air air is a composition of oxygen, nitrogen and various other gases. You can't see those gases. So if you can see anything that is definitely a matter but you must have done that till till class 10th mathematics because the vice versa is not true always but if you can see it you can easily and comfortably and and uh practically you can obviously say that this is a matter then that flame will also be defined as a matter because now we have defined matter that if you can point blank see it if you can see it it's a matter I hope I hope everybody got that if you can see it that's a matter now I will challenge that also how comment about thunderbolts and lightning the monsoon is already near us and many parts of India is is of already observing this this rainfall so during that rainfall you see those thunderbolts can you comment those lightning in the sky those thunderbolts are matter or energy they are matter or energy The thunderbolts, the lightning in the sky, they are matter or energy.
Lightning in the sky is matter or energy. Answer. Rajan is saying energy.
Uh then Nimsh is saying matter. Then Zyrus is saying matter.
Then uh Mahek is also saying energy, energy, energy. So many energy.
Thunderbolts are made of ions. Amit is saying uh okay so people are m mixed do you not matter it's energy so people are practically voting on energy uh beta remember if you can see it if you can see it if you can see it if you can see it I hope now everybody is answering if you can see it it's a if you can see it it's a matter but yes but yes but yes in In order to say these these thunderbolts actually what happens is one whenever actually what happen is whenever you have those lightning then during that lightning flow of billions of electrons takes place and that billions of electrons when they flow they superheat everything around them.
Both they superheat all the all the gaseous particles and and species around them and may make them highly temperature hottest temperature ions.
And actually that that those hottest temperature ions that are created during the during the exact time of lightning because of those billions of electrons actually you cannot even define those.
Yes, because you can see it so it's a matter but because you cannot even define that those characteristic with your s with your basic understanding of solid, liquids and gas because actually during that during that thunderbolts those thunderbolts are actually defining the the characteristic of a state of matter which is independently existing in nature. Yes, definitely you must have read that name plasma. Plasma has different property than solid, liquid and gas. Apart from solid, liquid and gas, you have two more physical two more states of matter which is plasma and both the Einstein condensate. Yes, they are not even uh there in your syllabus. But but but actually that thunderbolts are plasma and because they are having super supersonic energy and because of that energy BS there may be many people who will technically have a contradiction to it and they say this is energy. So, so what science is doing?
You people are are firsthand examples of of having this feeling that how science evolves. Remember that COVID time 2020 many of you have got those those vaccination shots and 95% maybe 99% of you ask your parents you are not even sure that if you have not taken those shots whether they have make some whether they had made some difference in your physical well-being or not. We are still not sure but still we did it because this is how science evolves beta. It is all hit and trial method. So we can't just be point blank and be definite about anything. This is how the the you must have seen that evolution of medical science around you after covid.
Similarly this way it has happened in the history also and that's how we have evolved and came around science. So again it's a controversial thing and definitely for for thunderbolts you can say they are both it can be said as matter also and it can be said as energy also. It can only be defined as matter in a more percentage of of of terminologies and conceptual understanding because it is creating the definition of a of a fourth state of matter which is plasma. But the reason sir then you are making things very complex beta the only reason I'm telling you this is because till date whatever atomic structure you have read that atomic structure is wrong. There is no dammer road around a nucleus where electron is making a circular path because mass of electron is 9.1 into 10^ - 31 kg. It is negligible. Maximum property of electrons can only be understood when you consider those electrons as energy.
So but electron has mass that mass we know also that's why I'm saying that even when we'll be when we'll be studying atomic structure we'll be saying that we do not know how these electrons are distributed. We just know the their the probability of finding those electrons. We are not even sure to this date that how and where the electron is actually situated. We just we have created a mathematical modeling around it. Yes, a beautiful mathematical modeling. But that modeling is also just giving us the probability of finding an electron. I cannot be sure. I am still not sure, science is still not sure that what is the exact atomic structure. we are just working on the probability of finding an electron. This is the beauty of science and because the science is so beautiful and because we want to we want to empathize with the beauty of science and that therefore for that for that for that level of empathy towards science we need to invest time not just by mugging things but yes by conceptually making discussions and this is what the intent is and this is what you should also do.
So let's I hope uh so again this candle is a matter this flame is a matter but this lightning yes because we have defined matter anything you that you can see is a matter so if you hold my neck I can I will say that uh thunderbolts and lightning is also a matter because you can see it but because it will only be defined as matter once you know what is plasma. Therefore for some conceptual justification somebody can even call it energy. So for for being safe for just getting those uh corona shots whether they are helping us or not we or scientific community will answer that these thunderbolts are both matter also energy also sir if it is coming in our uh innate examination these controversial questions will never come but still I'm again telling you if you grab my neck then I will be placing my single choice on matter why because we have defined matter as anything you can see is definitely a matter. So now sir, we know what is a matter. Anything that you can see is a matter. Then what will be non- matter? Non-matter is everything that has no mass and no space. It occupies no space and it has no mass.
Matter anything that anything that you can see is matter. And what is non-matter which has no mass and which will occupy no space. So next question, next theoretical and conceptual question for us that we have to list them as matter or non-atter.
So starting with electron, can anybody tell me? Hit the comment section. Can anybody tell me electron is a matter or energy? Now again I'm creating controversy.
Anything? Anybody can tell me. Anybody can tell me electron is a matter or energy.
Electron is a matter or energy. Come on.
Come on.
Come on. People are saying matter matter matter matter matter matter matter. Few are saying energy also. Now it is definitely a matter. Why sir? You said anything that you can see is a matter sir. We can't see an electron. It is so small. But beta you know now mass of electron is 9.1 into 10 ^ - 31 kg. But sir you said anything that you can see is a matter beta if I'm saying electron that means practically practically electron is always moving with such high velocity but if you are giving mass of an electron and if you are just talking about an electron then theoretically I'm just assuming that electron to be standing there and who are you because you are an electron you have definitely got a mass very less mass because the property of flow of electron is not that electron it becomes electricity When electron starts flowing it becomes electricity. When electron starts flowing with the speed of light they are not called electron they are called electromagnetic radiations. So if I have written electromagnetic radiations then I'm talking of electrons which are moving with speed of light. If I'm talking of electrons moving with high velocity in a metallic wire I am I cannot say them as electrons. Then they are named as electricity. So have I written electricity over there? No. Have I written electromagnetic radiations over there? No. Why you are getting these these these uh uh teachings from PW or whatever online platform inside your mobile phones or inside your laptop because we have got these internet connections from where the signals are getting transmitted. These signals are what they are electromagnetic radiations. What is this 5G speed? This is the frequency of those electromagnetic radiation. More frequency more energy. More energy no buffering. else um that those buffering is taking place that means the energy the frequency with which you are receiving these electromagnetic radiations are less energy less so I will be coming to your place buffering if you have got highspeed internet then because of because of the electronic IT advancement that we are having these quite reasonable internet packages that means these electromagnetic radiations are allowed to be circulated at high speed that means high energy so moving electron moving with velocity of light is not electron it is electromagnetic radiation moving electron with large speed but not with the speed of light that is called electricity and if I'm saying only electron I definitely mean it is mass so it's a matter I hope I hope we are creating that curiosity I hope okay Ana thank you Ana is saying he teaches very much better than my teacher. Okay, beta. Thank you for your uh encouragement, Ana. But now we want you to wear that white coat and celebrate that that achievement of getting that white coat from a prestigious come medical college once we'll be meeting in the in your result celebration day. So for that you have to start your working my friend. Chalob beta.
Okay. Okay. Okay. Chal chalo chal now density density is matter uh yes three chairs for cockroach jantaa party come on uh I know it is huge trend so cho hey come on now ch what is density matter or energy what is density matter or energy beta flame because you can see that flame now we or that flame is uh purvi is asking why we I mean a student asked the name has just just gone by uh that why flame is not both because beta fl you that flame that flame is only visible to your eye because of the combustion of gases that is taking place. If you burn a candle in vacuum and just give it oxygen so that the the the combustion can take place you will not see any light. The the only reason that illumination that light is coming is because of the combustion of the unburned carbon and the gases around it.
If you will not have any of those molecules which are going combustion, you will not see the illumination. Then candle will not be giving you any any illumination. The room will not be getting lightened up. So that's why you cannot say it's energy. It is definitely a matter because matter those molecules are getting combustion. Combustion is creating that illumination. That's why that flame was point blank matter and not energy. So what is density guys?
What is density guys? Yes. Yes. Now everybody is correct. Now everybody's correct. Okay. You are best sir. Thank you. Snow but beta. Come on. Come on. If I'm best then tell me what is density.
Have I communicated that that feeling of science inside you? Yes definitely all the people are correct. It is also matter beta. It is not non-matter. Why?
Because density is mass of any substance per unit volume. So mass of any substance. Now yes definitely you can't see density but beta density as a function as a mathematical definition is only defined as what is your mass occupied per unit volume. So who are you? You definitely have to need to have a mass and need to have some need to occupy some volume. Then only your density can be made into being made into effect and therefore since non-matter is which has no mass and no it obviously no mass will occupy no volume. So definitely to density also I would refer that it is also a matter. Point number three what is brain? Because you are bio student.
Because you are bio student.
What is brain?
What is brain?
What is brain? Come on. What is brain?
Matter or non- matter? Think about it.
What is brain?
Matter or non- matter? Let me pour some water by that time. What is brain?
matter or non- matter.
Yes. Yes. Now I have got response. Yes.
Because brain is a organization of a billions of tissues and cells. Those tissues and cells are obviously made of atoms and therefore brain is definitely a matter. You can see that brain, you can dissect that brain. Once I'm gone, you can obviously have this brain for dissection as uh as a sample. So brain is definitely a matter which has a mass and it is occupying a volume and once you are scoring well with your uh after your MBBS for your MD or for your MS examination, you will be given a specification and you can choose this brain. So you will be a brain surgeon.
So this brain is definitely a matter.
Moving to drop of rain. I'm not saying the phenomena rainfall. I'm asking that drop of rain. Sir that drop of rain is definitely those water molecules and those water molecules are H2O made of two hydrogen atom and one oxygen atom.
So that water molecules assembly is is a dra is a drain drop. So that that is also a matter sir definitely. Now last the last last two I mean yes last on this side then we'll be moving on to the other side. What is smoke?
What is smoke?
Smoke is a matter. Yes neurologist. Yes my dear neurologist.
What is smoke? Smoke is matter or energy?
Yes. Smoke is also matter because you can see it. Bingo. Definitely smoke is also a matter actually. Uh it is not it is definitely not a uh simple mixture.
It is called a colloid. What is a colloid? When the solute particle size is very less and definitely then then that solute particle is not called solute technically it is given this type of mixture is termed as a colloidal solution or simply colloids which has a where the solute are referred as dispersed phase and the solvent is referred as dispersion medium. So whenever you have some solid particles in gaseous air. So when solid in gaseous solid dust particles are existing in solvent of dispersion medium of gaseous in air then that is called smoke and obviously you can see this smoke. So definitely it's a matter obviously fog is also a matter not that tish tish fog but yes fog is actually H2O liquid the moisture content in air. So again it is also an example of a colloidal solution because the solute which is termed as the dispersed phase the particle size of those solute are less than 100 pometer.
Therefore they are not termed as a true solution they are termed as a colloidal solution. Definitely the surface chemistry chapter is removed from needs labors but still this much practical knowledge you should know. So obviously they both are also matter. Moving to the some other examples. Now you tell me what is time?
Time is matter or energy. Sir, this is point blank. This is quite easy us for now because if you can't see it, if you can see it, it's a matter. If you can't see me, you can't see me. Now aa one more question. John Cena is matter or non- matter? John Cena is matter or non-matter. N beta, no polls for today.
John Cena is matter or non-matter. Beta uh speed up. I do not wish to speed up.
Why? Why? I will. We are enjoying science. Let us enjoy science and and becoming a getting a good government medical seat will be a byproduct. Why we'll be focusing? Because sir, we are starting on time t equal to0. So we have hell lot of time for us. So let us make best use of it and definitely in order to enjoy your learning experience you do not have to do that hodgepodge. So relax. Yes, it is your teacher's responsibility that like I said I will not be discussing those laws of chemical combination which you can read from any or any other uh I mean let me not be you any and everybody your bayas and diis can also give you that law of chemical combination. I'm not telling you that I'll be leaving those concepts but yes I will be discussing important concepts so that in your DPPs also in in our batches I'll be giving more questions around that so that you practice the high weightage topics more and yes we will not be leaving any pennies so yes definitely we'll be treating all the chapters but this is my lecture flow this this is how it takes place that I keep the unimportant things separately so that in your copies also you know that this is where you should place your maximum attention and these these other se sections which you can just yes yes yes you should know everything as a as a as a a1 aspirant you should know everything but yes you should also know this segregation that which topics you have to give more importance and which less ch moving forward time is a matter of or energy time is matter or energy sir time is diff sorry not energy now I am distinct making a distinction as matter and non-matter So time is definitely a non- matter sir. Why? Because you can't see it. Because you can't see it. What is electricity sir? You already told us when you have discussed about electron because electron is a matter. So so flow of electron will be nonmatter because flow of electron is a property by which electron is flowing. And because that electron is flowing that means sir you can't see you can't see electricity.
You can't see electricity. Electricity does not occupy any so so sir it has no mass and it has no space. It is the property of flow of electrons. So it is definitely a non- matter. What is love, depression, anger? Sir all these all are emotions. Yes definitely they play they takes lot of energy out of you but they are not matter they because you can't see them. So they are also non-matter.
What is sound sir? Sound is definitely an energy. If I shout if I shout out in in your ear just by approaching you with so proximity then you're you're I mean you will just throw uh my face apart.
That means sir sound definitely requires lot of energy. But sir sound has no mass in itself. Sound does not occupy any volume. So definitely it is also a non-matter. What is light? Sir you already told us that when electron moves with a speed of light it is called electromagnetic radiation. And these electromagnetic radiations are making us uh when these electromagnetic radiations comes in a range of visible r of visible spectrum so that our retina can magnify that that image then those electromagnetic radiations are termed as light. So this light is also a non-matter. It is the it is a wave nature of electrons. So it is also a non- matter. What is human memory? Sir, your brain can be your brain can be you can become a brain surgeon but in order to make an impact on the on the feelings and memories I have you have to become a psychiatrist. So psychiatrist do not is not a surgeon. I mean yes after I mean yes there may be some I am an engineer so I do not know that detailing but yes working on the human memory so that human memory itself is not having any mass so yes definitely a lot of emotions lot of energy but no mass that's why it is also a non- matter what is heat sat obviously you can't see it so it is also a non- matter now I hope you can easily comment on the last one what is rainfall So droplets of rain are water molecules but s rainfall is definitely a non- matter. I hope we have invested much time and uh relevant time in the discussion of these matter and non- matter and I hope everybody's okay thank you for giving your okay chalo chalob beta I hope perfect perfect everybody now let us move forward with the basic structure sir but you said you will not be doing those basic I mean just the basic structure because they the the basic terminologies are important now what is the matter uh sir anything that has mass and occupies space And above all sir whatever you if you can't if you can see it it's a matter so you can't see John Cena so John Cena is a non- matter because you can't see him I mean as per John Cena says so John Cena is definitely a sir yes sir Michael Jackson matter he bet John Cena you says now you can't see him so John Cena is not a matter now now what the how are these matter classified sir these matter are classified as pure substance Class 9th basics and mixture. What are pure substances? Because I mean many teachers do not teach this. That's why a very basic thing but let me help you do it. What are pure substance sir? They can be element also sir they can be compounds also. What is an element?
Element are substances which contain only one type of atoms. Elements are substances that contain only one type of atoms. And what are these compounds? So compounds are substances that contain two two or more different kind of atoms but yes in a fixed ratio. So elements should contain same type of atom.
Compound should contain two or more than two type of different atoms but yes the the the ratio in which they are combined is always fixed. Now what is a pure substance? sub substances which contain only one type of either element or compound that for example if I have distilled water if I have if I have distilled water then this distilled water is just having H2O but if it is a tap water then that's this tap water will have H2O also and loads of impur also that is there in my surrounding so what is a pure substance it can be an element also it can be a compound also but it is existing independently not with another compounds or elements. So that is a pure substance. So pure substance can be element also and it can be compound also. Okay. What is a mixture? So this we know the mixture as in when when it is not pure. But this mixture can be homogeneous also.
Homogeneous as in when the solute and solvent are completely mixed and they are in same phase like your salt solution. And you have heterogenous mixture also where you can easily separate them by any physical method.
You just put sand in water. Just pass water through a seieve through a chney.
Obviously you will be separating those sand easily. So that sand and water is an example of hetrogenous mixture. Now coming to some basic questions around it. Now you tell me. Now you tell me oxygen.
The symbol of oxygen element is O.
In nature oxygen element exist as what sir? In nature oxygen element exist as O2 molecule. So the atomicity of oxygen the atomicity of oxygen in which it exist in nature is diatomic because atomicity is number of atoms required to form your molecule. But now you tell me O2 is a compound or O2 is an element.
O2 is a compound. Answer everybody. O2 is a compound or O2 is an element. O2 is a compound or O2 is an element.
O2 is a compound. I'm answering I'm asking so many times because I am watching the comment section. O2 is a compound or O2 is an element.
Element AIT is saying uh I'm not asking molecule in ia. I am asking compound or element.
Most of you are answering I'm not asking molecule beta. Yes, obviously it's a it's an elemental molecule beta. It is not a compound because remember what is the definition of a compound? Substance should contain two or more two or more kinds different kinds of atom. Is oxygen gas containing different kind? It is containing two atoms.
Agreed. But are these two atoms of the same kind or the different kinds? Are same kind. If they will be of the different kind then it will be called a compound. Yes, you can definitely say that this oxygen this is not a compound.
This is an element. Yes, to be very precise with your English, you can also say it's an elemental molecule.
This element is existing in the form of a molecule. But my friend, do not say it is a compound because what is the definition of a compound? You should have more than one type different type of atoms then only you will become a compound. I hope everybody is with me on this. Now similarly helium in nature exist as H E. So the atomicity of helium is one. So they are inert gases. Inner gases do not combine. So it in nature also it exist as helium. So its atomicity is one. Now what is it compound or element? Sir definitely it is also an element. And the elemental molecule of helium is also H because its atomicity is one. Now hydrogen s H2 obviously it is also an elemental molecule not a compound. Neon is ne the atomicity is two over here.
For neon sir it is also an inert gas. So it will its atomicity will also be one.
And definitely all these species are elements not compound. Yes you can say they are elemental molecule but not a compound. Now what is phosphorus in nature? Phosphorus exist as a tetraatomic molecule. Again a molecule.
So P4 is also an element not compound.
The elemental molecule of phosphorus is having atomicity four. Similarly if you talk of sulfur so sulfur exist in nature as octaatomic. So eight atoms of sulfur exist together to build an S8 molecule which is an elemental molecule again not a compound. This has a beautiful crown shape. Now what is chlorine? So chlorine exists in nature as Cl2. So again it's an element not a compound and its atomicity is two. I hope everybody's clear with me. Moving forward now because you know what is an element and what is a compound? Because you know what is an element and what is a compound. So can you now answer? Can you now answer 1 2 3 4 5 6 You have 12 examples. Can you answer quick?
Chal I hope yes yes yeah yeah yeah people are definitely investing their attention and focus on answering uh chalo perfect perfect everybody now let's see let's see let's see how many of you are correct and how many but good participation beta I'm super happy super excited that each and every one of you are participating so beautifully. Thank you.
Uh okay chal ch moving forward now sir you are asking about elements and compound.
Okay sir now we definitely know because this is just one type of atom. So this is an element s this is also an element definitely sir this is uh a sodium chloride the table salt is is formed of of sodium also and chlorine also that's why this is definitely a compound because more than one type of atoms are used this is also a compound what is ozone sir again although atomicity is three but this is this is assembly of just oxygen so that's why this is also an elemental molecule but it's It can't be called a compound. This is also an element. Sir water this is definitely a compound. Sir ammonia definitely a compound. Nitrogen although sir we know hydro nitrogen exist as a solid but still sir the the the elemental molecule is I2 diatomic but still it is just an element because it is assembly of just one type of atom. Again glucose fructose uh the the having same molecular formula but different functional group. Glucose is having an alihide functional group.
Fructose is having a ketonic functional group. So yes, they are isomers. We'll be learning about them in organic chemistry. But right now they are they are formed by different type of atoms.
So this is also definitely a compound.
Sucrose, your gana, your cane sugar, it is also a compound. Dry ice. Whenever you just wake up in the morning and open your refrigerator the once you open it you see those those those solid I mean yes it vaporizes quick quite sharply but that dry ice is those solidified CO2 molecule. So because it is a molecule molecule constituted of different atoms carbon and oxygen. So definitely this is also a compound. Moving to the last example which is diamonds. A diamond is a tetrahedy arrangement of carbon. So just carbon and because this is just an assembly of single one type of atom.
Yes. A an array a tetrahedral arrangement of carbon but only carbon.
Now so that means this is nothing but carbon solid. So it is also an element not a compound. So your precious diamond is also an element not a compound rather. I hope everybody is clear. Cho.
Moving to the next question. Moving to the next question. Now you tell me you have to classify what is a mixture and what is a pure substance. So this is quite easy. Why you are giving us this?
Because beta although inorganic P block S block has been removed from NCERTT syllabus but still advance so is love. J advance is in love with the the the single pages uh in in this J advance 2026 one question from paper one question for paper from paper two was directly just like neat examination it was directly a two pages reference of of of of NCERTT so yes advance love P block sir but we are neat aspirants but beta obviously you know the your neat examination so isn't love I I'm very sure uh after Sometime they are going to ask that this is given in which page? So they'll be asking page number 1 2 3 4 ABC D. So because yes NCERTT is your your for for a neat aspirant it is definitely a Bible and uh you should treat it as your religious book. So definitely you should have at least one NCERTT the hard copy. uh now because these inorganic things are important that's why I'm giving you these examples so that you whenever you write these things in your in your class notes at least try to remember them for a longer duration because this will be helping you because this will be making you a disciplined student and therefore uh that's why these example now obviously bronze is what sir it is a mixture of two it is an alloy it is mixture of two solid metals copper and zinc copper 88% zinc 12% so definitely it is not a pure substance And it is a mixture.
Uh I'll be discussing about gold separately. What is tap water? Sir, you already said that water once mixed with impurities the solid the salts that are existing in the region around. So definitely this is also a mixture. Now distilled water that means it is point blank pure water molecules H2 molecules.
So distilled water is definitely a pure substance.
Coming to brass or brass is also an alloy. Alloy of copper and zinc. So this copper and zinc is definitely making brass and alloy which is definitely a mixture. I hope you can retain this for in your memory that it is having copper but what percentage 66% it is having zinc around 34%. Good. Uh what is air?
Obviously air is a mixture because it is having nitrogen to the maximum extent but yes after that oxygen and various other gases. So that is also mixture. So because this is pure hydrogen you are talking of so this is also a pure substance. So element can also be a pure substance obviously compound can also be a pure substance. I hope now this basic classification you know a again a conceptual question again a conceptual question because now we are done with matter and we are not interested in law of chemical combinations as of now because atom is the smallest particle which is which has made up all the matter. It was postulated by Dalton and we all know that Dton law as of now is is is obviously not true because atoms are composed of electrons, protons and neutrons. All of us already know this.
That means that whatever law of chemical combinations we had which were based on Dalton theory which were based on Dalton theory they are also incorrect. Yes. And that's why they have got less relevance in the in your meat and J examinations also. Point number one. But sir then still why it these Dton's laws is still there inside in in our class 10th syllabus. And in fact your class 11th NCERTT also mentions about Dton's law they it also mentions about bore model.
You said sir there is no fixed circular orbit but still we we encounter this bore model because for single electron specy as in atoms which are just having one electron bore theory is still applicable which has been approved by the quantum theory which has now which is still now existing. We know atom because of theory called quantum theory and quantum theory also except that bore model is approximately correct but for not all for single electron species all the species who are just having one electron both model is still applicable and when you speak of of of macroscopic level as in when you generalize things as a whole these dial and bore model help us to understand the general idea of an atom the general idea of the basic calculations involved ing them. That's why that's why we'll be dealing with those law of chemical combinations later and obviously we'll be dealing with the atomic structure thoroughly with a independent chapter which is atomic structure but as of now we are just diving deep inside an atom deep as in not in the assembly electron proton neutron how they are distributed we'll be just talking about them generally generally as in as per the bore as per the bore model it has been communicated to us But but after that we'll be directly switching to mole concept. Why?
Because that mole concept is more is actually most interesting also and it is mostly uh the the time investment the investment if you are investing time then return of of of investment should be quite high. So just to get inside the idea of what is mole we are first trying to quantify atoms. So in order to quantify atom this is a question for you that how many number of oxygen atoms is present in a packet of globers salt.
Now beta please read the question properly. Obviously options are there in front of you. Acha aacha explain about gold. Okay. Okay I left gold beta. I'm sorry aa. So that frame I've already made that why I'm disc I'm focusing on atom but yes but yes before that I just left gold. So now what is this 24 karat gold actually? Because gold is a very precious metal practically also. So gold is quantified in form of carats. So let's say you have you bought a gold chain. What is the weight of that gold chain? Let us suppose it is 24 g. And if it is a gold chain then definitely you have you have asked your your jewelry shop guy to make a shape out of that gold chain. That gold chain cannot be cannot be having 24 g gold. Although it is 24 g gold chain but it will not be having 24 g gold. And your the shopkeeper will also be telling you that this is not 24 g gold. This is maybe 18 karat gold or 20 karat gold. Why?
Because pure gold is not workable. You cannot cut out designs. You can't you can't work. You can't make shapes. You can't draw ducts. You can't make it malleable. You can't work practically on pure gold. Then in order to work on gold, in order to make designs out of gold, you have to add impurities. And because gold is such a precious metal, then what is the scale we have designed for them? that if I'm having 24 g of gold chain and if it is an 18 karat gold, if it is an 18 karat gold, then 6 g of impurities will be added into it and 18 g of gold will be added into it.
Although the shopkeeper will be taking money from you as per 24 g, but it will be having 6 g of impurities and you are only agreeing to pay for those six gram of impurities because you want to show that gold chain lavishly outside. So that is that is a socializing expenditure. You are you are paying that shopkeeper. You know that this is 6 g impurity but still you are paying because you want to get a design out of you want to show off that gold chain. Else else you can buy 24 g of just gold bar. it will not be having any shape and then you will you just go to your uh any birthday parties or any celebration and you can expose that if by I mean yes obviously that will look not look socially good but this is how the classification of of of of quantifying the percentage purity of gold take place. So 24 karat gold mean you have no mixed impurity it is just pure gold. So because it is pure just gold just AU.
So this will be a pure substance and this 18 karat gold will definitely have six part of impurities. So it will be six part of some impurities along with 18 part of gold. This should be a mixture. So this is a mixture that is a pure substance. I hope everybody is clear with this. Anna chalo chal.
Perfect. Chalo perfect. Now moving to the question that we were discussing.
Now you have to answer now you have to answer that the number of oxygen atoms present in a packet of globers salt. So first of all to all my disciplined student I want you to learn the name also what is this glob's salt. Now what is this glob's salt? It is sodium sulfate decahhydrate as in Na2SO410 H2O.
What is this 10 H2O? This 10H2 is water of crystallization.
There are many solids there are many solids which solidify in practical nature using water of crystallization.
This these water of crystallization as in these water molecules actually for example let's say this is sodium sulfate because ionic compounds are pure solid sir. We already know it. Ionic compounds are pure solid. We already know it.
But once you have these ionic compounds, sir, solid means the constituents are so close to each other. So definitely these constituents are very much close to each other. Agreed?
These constituents are very much close to each other. But still you can't you can't fill these gaps. So that means these solids will have some interstitial gaps. If these gaps are also filled then the then the lat then the percentage packing the packing efficiency of the solid will increase and because everybody whenever they will form a strong lattice they will release energy.
So energy release that means energy of the system will get reduced that means the solid will have effective packing.
The same thing happens when you construct your new home. the the cement that is there in your new home whenever the the flooring takes place out of that cement then that floor that cemented floor is is poured with water for 5 days 10 days why because these water of crystallization now what these water of crystallization do so they just get inside they just get inside the voids and these water molecules after getting inside the void in fact increases the packing efficiency increases the packing efficiency of the solid and makes it a strong solid and such solids are called crystalline solid.
Such solids are called crystalline solids and obviously they have better packing efficiency. So these solids are making your structure quite happy quite strong. I hope everybody is with me on this. Now talking about the phys talking about the inorganic side and obviously this is this is a very beautiful topic topic from solid state again solid state is still a topic for J advance but not topic for J means and need but still this much knowledge at least you should have moving to the question so that we can build our confidence around atoms so how many oxygen atoms we have uh I didn't say it was a single correct question beta actually Answer is C also and D also. Most of the student are answering C. They are not incorrect.
Beta that C is not incorrect but it is C and D. Why sir? Look at the language. It is asking you number of oxygen atoms in a packet. Is it mentioning how many molecules of global salt are present in that packet? No sir. So why you have assumed that this packet was just having one molecule? Yes definitely all those who are answering 14 one molecule is having four oxygen from here one molecule is having four oxygen atoms from here and oxygen molecule is having one oxygen atom but I have 10 oxygen molecules so that means one molecule will definitely have 14 oxygen atoms but sir are you confident and sure enough that the complete that the complete packet is just having one molecule Now, so if it is having two molecules then oxygen atom will be 14 into 2. If it is having if it is having three molecules then 14 into 3. Then sir if there is an option of 14 into three then that we should take that also. Yes.
In fact if you would have an option of 14 times of n where n is number of molecules present in the packet then this should be the most correct option.
This should be the most correct option.
But here C also and D also can be your answer. Sir, but this is a need question. I am not talking about need questions. I am talking about building confidence and building logic right now.
So did I say it's a single correct question? No sir. I hope everybody is clear with me. 14 but 28 I didn't understand. Did anyone get that part?
Beta again I'm telling you in ask me.
See read the English of the question.
What happens with with theoretical questions as beta word they are called word problems. So actually word becomes the only problem. Actually word becomes the only problem. So just read the word beta. The question is saying number of oxygen atoms in a packet of globers salt. You have a packet of globber salt.
Globber salt is having a formula Na2SO4.
NH2O. Now is it written in the question that the packet of global salt is having just one molecule?
It is a packet containing global salt.
What is making you believe that it is just having one molecule?
You are not sure it is a packet containing global salt but how many molecule? I do not know. And because I do not know so definitely I know one molecule has 14 oxygen atom. So let's say n is the number of molecules of globber salt present in the packet of glober salt. The number of oxygen atoms will be multiple integral multiple of 14. 14 is also integral multiple of 14.
28 is also integral multiple of 14. And 14 e is also an integral multiple of 14.
So this if this is written then I will just take this because this is the best answer. But if 14 and 28 both are given and this is not given, I have to take 14 also and 28 also and this J advance does it. J advance ask you multiple correct questions. Yes sir, we are not preparing for J advance. Why you are you a J? Yes I obviously beta I cleared J back in the year 2007 my rank was AR 6,000 but yes my time there were only six IT. I have cleared I've got done my beta from electrical engineering from an IT kuretra but but beta if you are planning to run 100 m race you will only practice running 100 m daily obviously you will run for kilometers each day so that you can plan for the D-day and obviously with the level and uh content with which neat examination is throwing questions at you you should also learn physics and chemistry as well I'm Not saying J advanced question everything but yes you should also elevate the level with which you are studying. So I hope everybody's perfect.
Shallow integ what is integral multiple as in some integer multiplied by 14.
Integral multiple means some integer multiplied by now the packet will have one molecule. So 14 and two molecules 2 is also the next integer after 1 is two.
So 14 into two. Next integer three. So 14 into three. Next integer four. So 14 into 4. So on and so forth. So that is called integral multiple. Okay sir.
Please repeat case of 24 karat gold. See better beta. What [snorts] is that 24 karat gold? Uh let me borrow a blank slide.
Huh? See talking about that 24 karat gold again because to BSP suppose let's say let's say I have 24 g of gold chain or rather I have 24 g of gold bar let's say this is a beautiful chain chain which some design you have asked the jewelry shop to make out for you. So this is a chain. What is the weight of this chain? 24 g and I have just no design just a point just a blank uh decent looking and old looking gold bar.
So this gold bar do not require any designing. This is just you put your uh molten 20 to molten gold put that in a mold solidify it and sell it. So this is just a gold bar do not requiring any artistic design. So I do not have to work on this gold. But if I want to curve shape out of the gold molecules then this this side and this side has to be joined with each other. And in order to join the two sides, you have to create that locking. That locking requires you to work on your gold. That working can only be done once you add another metal. Those locks are not of gold. They are of the impurities because pure gold is not workable. It is a practical story about gold. It is a practical story about every metal. Even when you when you have your steel now, your pure iron, pure iron is also not workable. We add impurities of carbon, silicon, any number of impurities you add in iron and then then that iron becomes steel. The steel is more expensive because in factory iron is mixed with fixed um percentage of impur and then that iron becomes workable.
That's why you make so many designs of out of your gates but pure iron gate cannot be made because pure iron is not workable. So this is a practical side about uh about the metallergy of metals.
H so let's say if it is 24 karat gold chain and and uh it is 24 g gold chain and it is written first thing is it has it it needs to be added with some impur because it can't be worked upon. So this can be a pure substance. But here let's say the shopkeeper has told you it is 18 karat gold.
So that means out of the 24 g total 24 g 18 g will be pure gold but out of this 6 g will be impurities because the carrot gold chain you have bought it of it is of 18 karat gold.
I hope so. That means that this is gold also and other metals also. And then because it is containing not not single element but more than one element. So this will not be a pure substance. This will be rather a mixture.
I hope everybody is clear with me.
Moving forward I'll not do a neat question. Let me rather do a J mains question. How? Now coming to the practical side. Coming to the practical side.
Coming to the practical side. So because you asked so just a a a small J your okay this is a need question 20 to 25 question only that Dton atomic theory could not explain which of the following. Sir you already told us Dton theory is incorrect because it said atom is the mo is the smallest particle and you cannot break an atom. Sir we know we can break atom but sir that we'll be discussing about atomic in atomic structure. So how much Dton theory we should know that uh atom is the smallest particle although this is this is regarded incorrect but why we still study it because in general for calculating uh for calculating number of molecules for calculating the atomic masses that is calculation of atomic masses is also a task for us because our atoms are so small and moreover in nature they do not exist independently.
Therefore we have to design a mechanism to weigh them. So at least let us focus on atoms first and therefore still now although incorrect but we study those law of chemical combinations and Dton's law sir all the law of chemical combinations are based on Dton's law. So what the Dton atomic theory could not explain sir law of conservation of mass although incorrect but it is a conclusion of it is based upon Dton theory. So law of constant proportion is based upon Dton theory. So law of sir what are these laws? I'll be discussing them in my classes but sir this is the first class. So let us generalize because these all things we know from class 9th and 10th law of gaseous volume sir about gas gas law which is PV equal to NRT which is PV equal to NRT. So Gusk law tells us that at constant temperature and pressure at constant temperature and pressure R is always a constant which is termed as universal gas constant. So at constant pressure and temperature, volume of gas is directly proportional to number of moles.
Sir, this has nothing to do with the existence of matter as a smallest particle of atom. Sir, this has nothing to do with Dalton's law. This is an independent statistical analysis that yes, we'll be studying. But this is based upon ideal gas theory. This is based upon gaseous law and it has nothing to do with Dalton's law. So the question is asking us Dton's atomic theory could not explain they can explain ABC but obviously it cannot explain the gaseous law. Therefore D will be your answer. Good.
Good.
Huh? So one student is saying sir explain beta. Now somebody's saying explain global salt again that water crystallization thing and somebody is saying and somebody is saying is sir do a J question or need question. So beta obviously uh uh once the class is done so you can watch the recording. So let me yes I will be uh finishing around in next uh 10 15 minutes. uh but yes beta I want to brush upon and touch upon the the base the f for first class of your class 11 you should at least know that what was the problem at that point of time which scientists were facing during the time of dalton only the electrons protons and neutrons discovery was not happened but yes during the time of dton's only and even after the discovery of electron proton and neutron during that time also there was a problem what is the problem how to quantify these matter quantify as in how to measure them. So once we started measuring then the very first problem we faced the very first problem we faced was sir atom exist in nature not independently only in nerd gases do but atom exists in nature as compound. So how come we will weigh that compound? Similarly like for example I have I have very few water in my glass. I can see water but sir I cannot see H2O. Can you see H2O in water? No sir I can't. Even you can't.
So the spectroscopy can tell us that it is oxygen two one oxygen and two hydrogen in one molecule. But I cannot see those hell small molecules. So what shall I do?
How can I measure these atoms? This was a problem and this problem was solved by international union of pure and applied chemistry. And they said and they said that if you want if you want to measure the atomic masses if you want to measure the atomic masses of these atomic species the atomic masses of these atomic species then what shall you do?
What should you do? You should think of a weighing balance. the the shopkeepers around you, even the street uh vendors who are selling vegetables across the road, what they have with them. So, they have a weighing balance. They just keep that weighing balance in their on their on their head. They just swing it. They just put one maybe 1 kg or half kg iron bar on one side and with respect to that known mass, they can calculate any unknown mass. They can calculate any unknown mass. Any unknown mass as in you can buy 1 kg of fruits, 1 kg of vegetables, 1 kg of any and everything.
So with respect to a known mass, you're measuring any unknown mass. Now you must have observed that whenever they used to give give that give that uh vegetable or fruits to you the the swing you prefer that the swing should not come in between. It should be just lying more on the side of the vegetables or fruits that you're buying. That means even if you are paying for 1 kg, you are approximately getting more than 1 kg.
Yes, you should not do that because they are street vendors. They are uh just I mean without any shadow or or any air conditioner around them. But still this is the uh society that we have built that we don't pay for that 1 kg once the swing is on the iron bar side. We consider that this is 1 kg once it is more than 1 kg because we are customer I mean yes uh that that that thing just has a different psychology different moral science behind us but we are not learning moral science over here so I'm just discussing that practice that what is that practice with respect to a known mass you can calculate any unknown mass point number one this is what IUPAC have done because you cannot separate and because atom and molecules are so small so you cannot measure them you cannot weigh them then do what? With respect to a known mass you can calculate atomic mass of all atom. So now what is this known mass? The more known mass the reference mass that was chosen was of the simplest atom which is hydrogen because every atom was heavier than hydrogen. So it will be some integer time I mean not exactly integer but ultimately more than hydrogen. So you can be 2 * 3 * 4 * 5 times maybe 4.5 * 5.5 * whatever times of hydrogen you can even be more heavier than hydrogen.
Therefore the data of masses of the relative masses that you'll be getting will definitely be not be a 0 point something because you can't learn that 0 point something values. So that's why the mathematical reference best reference was hydrogen. But there was a practical problem with hydrogen. If you are measuring mass of atoms with respect to hydrogen then hydrogen needs to react with all other atoms. So that was the problem that chemistry community chemistry uh builders made and and had that hydrogen was not reacting with everybody. So if hydrogen would have reacted with everybody you could have measured those elements with respect to hydrogen. So now I need a reference which reacts with everybody.
The reference chosen were were there were many references like oxygen but oxygen has a problem of isotopic effect.
What is isotope? Elements having same atomic number but different mass number.
Like for example chlorine in nature chlorine has atomic number 17.
Chlorine has atomic number 17.
But mass number of chlorine is either 35 also and 37 also. So what is this atomic number and mass number? You said you will be teaching atomic structure in the next chapter but at least this much 910 knowledge you should have. So let me summarize it for you. If I have an element X then zed represents atomic number and A represents mass number.
This atomic number represents number of proton. This mass number represents number of proton plus number of neutron.
So what at least what is your mass? Mass will be decided by mass number that is proton and neutron. So number of protons is same but obviously number of neutrons are different therefore you have different isotopes in nature. So let's say oxygen was similarly oxygen every element has isotope. So let's say if I'm measuring today then I am getting with respect to oxygen 16 next day I'll be getting with respect to oxygen 17 next day I'll be getting with respect to oxygen 18 sir that means every day the masses will change. No sir we need a scale which will not have this error also. So first requirement was for choosing a reference. First requirement was you should react with everybody.
Second requirement was your the the relative masses that should come will not should not change every day. It should be fixed.
So the reference I mean scientists become mad about it. And finally the reference that was selected was carbon because carbon one reacts with all other elements. Second, the C12 isotope of carbon has a percentage occurrence of more than 99%. So the chances the probability of making error was just even less than 1%. Therefore even sir we do this in while going in the market also even with the digital balance once you go to a general store or a kirana store even with the digital balance you pay for 1 kg dal once you see 1.00 00 something. So that average we do practically also we the shopkeeper do not give you 1 kg of dal by making you stand no it should be 1.000000 0 you you have an habit and shopkeepers also know this that you will understand it is 1 kg once it is more than 1 kg so that is that approximation even we have in our practical life and that approximation science also has in the in its practical life that the reference which is carbon is the C12 isotope is also existing in nature with a percentage of more than 99% not 100% but yes making 1% error is comfortable for us but still sir I need hydrogen mass in the denominator. So in order to convert mass of carbon equal to hydrogen to have a mathematical win also. So what we have designed the formula we as in the international community of pure and applied chemistry what they have done is the reference is carbon because it reacts with everybody and uh error the the probability of making error with the calculation is also less than 1%.
But because mathematically I want this denominator to become mass of hydrogen.
That's why I and because carbon is 12 * of 12 times heavier than hydrogen. So I multiply 1 by 12 in the denominator.
This will mathematically this will mathematically make this denominator mathematically it is nothing but mathematically it is nothing but but it is mass of one hydrogen atom but theoretically it is 1 by 12 into mass of C12 isotope. So what we have done sir we have defined the relative atomic mass. What is the relative atomic mass? Mass of one atom of any species upon mass of one hydrogen. Why not one hydrogen written? Because that reason you already know. So what is written?
1x2 into mass of C12 isotope. What is mass of one hydrogen atom? Sir, one hydrogen is just having hydrogen is just having one proton and one electron. One proton and one electron. So approximately mass of one hydrogen is also 1.66 66 or 67 into 10^ - 24 g.
I hope everybody is clear because hydrogen is having just one proton one electron add mass of one proton and one electron it is somewhere around this in terms of gram. That means sir this reference this denominator was capable of measuring all atoms with respect to this denominator. And because this denominator was so much useful therefore initially it was it was these definitions werea has came into existence in time of dalton. So initially this denominator was termed as one dalton but after that this this denominator was termed as one atomic mass unit. So it was termed as one dalton initially then it was termed as one atomic mass unit and now these days it is termed as 1 U which is unified mass. 1 U which is unified mass. So let me write this only because this is the most famous uh unit that you generally see around in your examinations. So that means s denominate this is relative atomic mass which is ratio of mass upon mass. So it will be dimensionless. So this relative atomic mass will be dimensionless.
Numerator is mass of one atom of any substance. So numerator will be atomic mass and this denominator you have already said is u. That means s atomic mass of any specy will be equal to its relative atomic mass which is how many times I'm heavier than hydrogen into into this u because numerator will be equal to ratio into denominator. So what is this denominator? you I hope you now know what is the definition of atomic mass and you know practically you know one thing practically sir what is atomic mass mass of an atom atom is consisting of what nucleus and revolving electron nucleus is having proton and neutron and electrons also how many electrons so number of electrons will be equal to number of protons so number of electrons and protons will be equal sir what is this This is nucleus having protons and neutrons and protons and neutrons are collectively known as nucleons.
And why I'm specially telling you this nucleons and why I'm specially telling you this because mass of proton is approximately equal to mass of neutron which is approximate to equal to that only 1.67 1.66 66 into 10^ - 24 g and mass of electron is much is is very very very very less. How much you already know this 9.1 into 10^ in terms of gram it will be 28 g. So if you just do the ratio then mass of proton or either neutron because both are approximately same upon mass of electron is approximately 1837 is to1 as in as in sir if one electron is 1 rupee mass then one proton and neutron is 1,837 rupee mass if you go out to buy a genes or something let's say the MRP of the genes is 1,800 or maybe 1850 Maybe sometimes the shopkeeper can offer you a chai a coffee he will not take another 5 10 rupees that means 5 10 rupees even while purchasing they do not consider so you tell me while calculating mass let's say this is an atom and you want to calculate the weight of this atom whether this 1 2 rupee will make a will make any difference mathematically no sir so that's why after learning this we concluded that atomic mass of every and any species will be just mainly decided by the number of nucleons.
Number of nucleons. Practically this relative atomic mass will not be an integer. It will be some mathematical some decimal values. But sir, what we learn? Because those d decimal values are approximately equal to an integer.
And what is that integer? That integer is the number of nucleons. Actually mass of carbon is not 12. It is 1200 1200.
But why do not use that 12.00001?
Because ultimately why I'm interested in just just that 12 because now we know this common sense that whenever you measure an atom sir its mass will be predominantly decided by just the nucleus nucleons which are combination of protons and neutrons. So what is atomic mass of hydrogen? One. Why?
Because it is having one proton and zero neutron. So number of nucleons is 1 + 0 1. What is relative atomic mass of carbon? Sir 6 + 6 as in 12. What is relative mass of nitrogen? Sir 7 + 7 as in 14. I am not saying if you practically calculate the relative atomic mass as in with respect to the weighing balance after doing that experiment you will not get 14 you will get 14.00 00 something or maybe 13.9999 something. Yes, you are writing 14 because you now practically know that atomic mass for an atom will largely what integer it will be coming out close to? It will be coming close to the number of nucleons. But sir, is it always true? N most of the time it is true. But many times it is not.
Therefore, we'll keep this thing in mind that all these relative atomic masses are average. They are average. And with God's grace, this average is an integer.
What is that integer? The the number of nucleons the the number of not mass of nucleons, number of nucleons, the number of nucleons. But sometimes it is not like in case of chlorine and obviously we'll be discussing those average masses thing also. But yes, that we'll be discussing in our next class. So yes I could not I could not reach huh beta I know I wanted to make most of this uh free class because from tomorrow or from from next class we'll just just be having our dearest Arjunas and because I know many of the students of past of class 10th just entering class 11th are searching here and there that's why I wanted to make best use of this first class and uh I tried I Hope I succeeded but yes I wanted to discuss those moles also but but nevertheless uh the time is up. So we'll be meeting inside a batches and definitely it will be more structured uh because yes uh then we when we'll be in our batches we'll be very calm although we'll be practicing very hard but yes it will be more structured because we will be meeting periodically practically regularly. So time will be our best friend and but all those students who are who have not yet enrolled for Arjuna need I wish you all the best. I suggest you should do it but if not do whatever but beta please have a structured study each day because no day is going to make a Taj Mahalo for you but each day will definitely make one for you. So with that thank you. I hope you will do great with your professional your neat career. And with that, this is me, Gorav Singera, signing off. So, bye-bye. Take care and I will see you soon. Bye-bye.
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