[Music] hey all welcome to homeschool and i am with class 11 chemistry chapters started with first chapter that is basic concepts of chemistry where i have already finished introduction part we studied about the matter classification of matter properties of matter right and various physical quantities that we use in chemistry to describe matter right a few physical quantities and their units are very very important to remember and now coming to the next concept that is scientific notation which is a very very important concept because i told you some of the chemistry chapters which come under a branch of chemistry called physical chemistry will have numericals okay even for the competitive examinations so they will ask numericals from these physical chemistry chapters see while doing a numerical you must know how to convert the digits into scientific notation say let me tell you what is the scientific notation and why do we use this scientific notation okay say for example chemistry is all about small very very small numbers or very very big numbers okay say for example when oxygen gas combining with hydrogen gas you will get water isn't it say i will be telling you uh when hydrogen gas combines with oxygen gas you know you will get something like water that is h2 okay so how do i balance this equation balance this equation so when i put 2 here i have to put 2 on the hydrogen of reactant isn't it see i can explain this reaction in one particular format i would be telling you 2 moles of 2 moles of hydrogen gas combines with combines with one mole of oxygen gas okay to give two moles of water now you would be wondering what is this moles okay say normally speaking what we can understand from the reaction is two molecules of hydrogen combines with one molecule of oxygen to give two molecules of water see we know how to tell a reaction in the form of molecules so looking at the equation for your level uh you would be telling that two molecules of hydrogen reacts with one molecule of oxygen to give two molecules of water okay no doubt reaction happens in that way only actually speaking crores of hydrogen molecules would react with crores of oxygen molecules to give crores of water molecules but they react into is to one ratio okay they react in two ways to one ratio so in a simple way we would tell two molecules of hydrogen reacts with one molecule of oxygen but actually speaking crores of hydrogen should be there and crores of oxygen molecules would be there in whatever amount of gas that you take okay 10 ml or 20 ml whatever okay and so many molecules would react right so that is the reason instead of molecule we say two moles of hydrogen gas combines with one mole of oxygen gas to give two moles of water okay so what do you mean by this mole here mole is just a number guys say just like dozen what do you mean by a dozen dozen in the sense 12 if i say dozen bananas what do you mean by that 12 bananas dozen apples in the sense 12 apples isn't it say like dozen you have a mole okay so mole is just a number just a number so which number is called as a mole you know what do you mean by mole is 6 0 2 2 and when you put 20 zeros 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 you know this much big number t is called as a mole just like 12 in the cents doesn't doesn't mean 12 no like that mole mole means this much big number so if i say one mole of apples means it is these many apples so can you uh give a particular name for this number right how many crores it is can you be able to tell me how many crores it is okay see this much big number is your mole see one mole of apples is these many moles of apples one mole of pens these many number of pens it is these many number of pens so that's what we mean by moles so atoms are very small crores of atoms would react with cross of another atom to form crores of molecules okay see it's all because the atom is so small and in many numbers it is reacting so we are using this much big number okay when we come to the atoms see if you have to write this much big number it takes lot of space in a book yes or no and it's very much inconvenient to write such big numbers okay chemistry is all about dealing with this much big big numbers okay and one more example i'll tell you okay see i have measured size of size of hydrogen atom okay size of hydrogen atom you know what is the answer i got for size of hydrogen atom 0.000 1 2 3 4 5 6 7 8 9 10 uh 11 3 8 5 you know so this much is the answer i got when i measured uh your size of hydrogen atom is this much meter i got okay you you see how much big number it is i mean it's a very small number time 0.000 after that three eight five you know such a smallest number but to write that it's very much inconvenient right with lots of zeros right so chemistry is all about dealing such big numbers actually to write them it is very much inconvenient uh it's very much uncomfortable right so that is the reason we use a shortcut way of representing a number okay so this is short cut way of representing representing a big number big number in a simple form in a simple form is called scientific notation okay so what is that a simple way of representing these big numbers we represent these numbers in the form of n into 10 to the power of n okay say in this format we will represent such big numbers okay in what format n into 10 to the power of n okay so whereas small n is exponent it is exponent okay whose value varies from minus to plus it can have minus value as well as plus value okay n is an exponent can have can have minus value or less well clear and what about this big n big n can have a numbers in between one point zero zero two nine 9.999 like n can be any number between 1 and 9 majorly clear say such big numbers if you want to uh write them in a simple form we use a scientific notation scientific notation is always in the form at n into 10 to the power of n whereas n is exponent it can be a negative value or a positive value right and whereas big n is nothing but it's a digit which can exist between 1 and 9 clear so this is a simple idea on scientific notation right and now let us try to write this number in scientific notation form so this is all about your scientific notation so how do you write this mole mole in the sense 6 0 to 2 and 20 zeros this much big number is called as a mole okay so any chemical reaction we do it in the form of moles okay all that you will understand little later very very clearly and now just concentrate mole is just a number which number it is it is this big number now if i want to write the same number in a simple form that is in the format of n into 10 to the power of n format how do i write so what i will do is say this much big number here can i write this number dot 0 right so i can introduce a decimal point here with 0 this is how i can write the number and now this decimal point you know i will shift this decimal point i will shift you know towards the right side and i will keep the decimal point here i am bringing the decimal point from here to here okay so when i bring the decimal point from here to here what can i write my answer as i can write it as 6.022 into right i told you what is your capital n value it is 6.0 i told you your capital n value can be between 1.002 9.99 so 6.022 into 10 to the power what is the exponent you will write here uh how many digits you have shifted 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 right so i'll be writing 10 to the power of 23 okay and i told you this is the value of small n and i told you small n can be a positive value and negative value here actually it is plus 23 okay whenever you shift decimal point towards your left side right so if you stand like this this is your left and this is your right so when you shift the decimal point towards the left then you will write the exponent as positive value okay so this is the scientific notation uh when you write this big number in the simplest form so what do you mean by one mole it is six point zero two two into ten to the power of twenty three particles is what we call one mole okay so now how do you write this number into scientific notation say this number say now i will shift this decimal point towards here after three see this is the first digit right after so many zeros this is the first digit so after three i will put the decimal point decimal point previously it was here this one i am shifting to here so how i can write this 3.85 into 10 to the power of how many digits after i have shifted the decimal point 1 2 3 4 5 6 7 8 9 10 11 12 right so i can write 10 to the power of minus 12 meter okay see you have got a exponent as a negative value here so when do you write it as a negative value whenever you shift your decimal point towards right side okay so here you are shifting your decimal point towards right side so whenever you shift a decimal point towards right you will write the exponent as a negative value okay so this point is very very important if decimal point if decimal point is shifted as shifted to words towards left then n is positive right so your exponent value you will write it as a positive value okay look at the mole case you shifted your decimal point towards left okay so how many digits before you have shifted how many digits left side you have shifted 23 so that's why 10 to the power of 23 it is plus 23 because you shifted towards the left side similarly if decimal point is shifted towards right side then your exponent value will be negative okay you can see in the second number what you have done you shifted this decimal point towards your right side i mean from here you have brought it and kept here after three so how many digits after you have gift it's 12 digits so minus 12 we have written right so this is how we have to convert the bigger numbers into simpler form that's what we mean by scientific notation okay and let us do some work out i'll give you certain examples and let us try to convert them into scientific notation first see here are few numbers let us convert them into simple form that is in scientific form okay look at the first number so how can you write this in a simple form you see here is the first digit after this all these are zero so except zero which is the digit here 4 so after 4 you have to keep the decimal point previously the decimal point is here so this decimal point you are bringing and keeping after 4 so how can you write the number it is 4.8 into o you will write it in the form of exponent form right 4.8 into 10 to the power of how much is the number you will write about it it is one how many digits after you are keeping the decimal point you are keeping after four in the sense how many digits you are moving one two three four five so you will write it as five so can you tell me whether it is plus five or minus 5 so what did i tell you if you are moving your decimal point towards your right side then you will indicate with negative exponent it will be negative exponent so when you are moving your decimal point towards the left then you will indicate with the positive exponent so this you should never ever forget so you moved your decimal point towards right side if you are moving towards right side you know you should indicate it as minus 5 so if you convert this number into simple form you can write it as 4.8 into 10 power minus 5 okay now coming to this number so this number is a very big number right 2 3 4 0 0 0 0 see now this number if you want to write it in a simple form how do you write say which is the first digit 2 so here you have to keep the decimal point previously if nothing is there then it's nothing but 0.0 right so this decimal point you're shifting where you're shifting here after 2 so you will write this number as 2.34 into 10 power how many digits you have moved 1 2 3 4 5 6 right so 10 power 6 now you have to decide whether you have to keep positive or negative sign say you have shifted your decimal point towards left side that means you should keep the exponent as positive so you will be writing it as 2.34 into 10 power plus 6 okay so next one this one 8 0 0 8 so how do you write it in scientific notation format this number i can write this way right now it's like the decimal point is here and this point i am shifting here so i can write it as 8.008 into 10 power how many digits you moved 1 2 3 so 10 power 3 so plus or minus you moved towards your left side so it will be plus value okay so similarly how do you write this in a simple form i can write it as 5.0 into 10 power you know i i kept a decimal point previously it was here this one i kept like you know here right so how many digits you move 2 so 10 power 2 plus or minus you move your decimal point towards left side so it is positive right and coming to this number how do you write it as so if this number is actually it's i can i can write it as this match 0.0 now this decimal point where am i moving i am moving it i'm keeping it after 6 so i can write this number as 6.0 into 10 power how many digits you move 1 2 3 4 5 6 7 8 right so 10 power 8 positive or negative it is positive because you moved your decimal point towards your left okay so just keep it in mind if you're moving a decimal point towards left you know keep the exponent value as positive if you are moving your decimal point towards your right side then that your exponent value is minus okay so this is how you can convert a bigger numbers into scientific notation which is nothing but a simple form of expressing some bigger numbers okay and now uh let us learn how to do multiplication for this scientific notation uh you know division as well as addition and subtraction let us see how to operate these mathematical operations when the numbers are in scientific notation format is first let us understand how to do multiplication of numbers in scientific notation say for example you have a number something like this 2 into 10 to the power of 5 okay into 3 into 10 to the power of 6 so how do you multiply this it's very simple first you multiply 2 into 3 okay then then what you have to do you should do 10 to the power of 5 into 10 to the power of 6 this is how you write okay separate the digit multiply the digit first 2 into 3 then separate the exponents like 10 to the power of 5 into 10 to the power of 6 this way you write after that we know this 2 3's are 6 okay so 6 into it will be 10 to the power of 5 plus 6 right so you all know in the algebra there is a formula a to the power of m into a to the power of n is equal to a to the power of m plus n you will do isn't it so same formula 10 to the power of 5 into 10 to the power of 6 so you will be writing it as 10 to the power of 5 plus 6 you should add 5 and 6 okay so what is your answer 6 into 10 to the power of 11 6 plus 5 is 11 so your answer is 6 into 10 to the power of 11 okay so this is how you have to do the multiplication okay so now let us take one more example 5.6 into 10 to the power of 5 into 6.9 into 10 to the power of 3 so how do you multiply this this number so how do you do first let me write 5.6 into 6.9 together right after that separate these uh exponents 10 to the power of 5 into 10 to the power of 3 so how much is 5.6 into 6.9 it will be 38 point if you multiply 5.6 into 6.9 you would be getting 38.64 into 10 to the power of how much 5 plus 3 you have to do here so it will be 8 okay and again you can simplify this say this decimal point if you bring after 3 okay if you shift this decimal point here so how can you write the same thing i can write it as 3.8 into 10 to the power of 3.8 i'm writing so how many digits you have shifted one digit and you shift it towards the left side right so when you shift it towards your left side and one digit i shifted so 10 to the power of 1 so will you keep this one positive or negative you've shifted towards your left side so it has to be positive so 10 to the power of 1 into this is there 10 to the power of 8 so you would be writing it as 3.8 into 10 to the power of 1 plus 8 is 9 so your answer is 3.8 into 10 to the power 9 okay so this is how you have to do multiplication when the numbers are in scientific notation okay and now coming to division let us do division when numbers are in scientific notation okay say for example you have 10 into you know 10 to the power of minus 6 divided by 2 into 10 to the power of plus 5 so how do you do first you divide this with this so how much do you get ones on five right so 5 into how do you write this uh do you remember in an algebra you have a formula a to the power of m by a to the power of n is equal to a to the power of m minus n isn't it okay say similarly uh two ones are two phish so five into you will be writing it as ten to the power of minus six minus uh you know 5 right so your answer 5 into 10 to the power of minus 11 right so this is your answer so when it is in a division you know this minus this number you have to do right just you are applying your algebraic formula that's it so this is how you have to divide when the numbers are in scientific notation and this is how you have to multiply when the numbers are in scientific notation and now we will discuss about addition and subtraction with numbers in scientific notation see guys here is an example for addition when the numbers are in scientific notation see you have to add 6.1 into 10 power 4 plus 2.2 into 10 power 3 right say here one condition is keep the exponents in same number if here is 10 to the power of 4 here also you should keep it as 10 to the power of 4 okay or here 10 to the power of 3 is there or you convert this 10 to the power of 4 into 10 to the power of 3 okay anything you can do you can convert 10 to the power of 4 as 10 to the power of 3 or 10 to the power of 3 as 10 to the power of 4 but the thing is both exponents have to be in same number okay so what i will do is i will convert this 10 to the power of 3 type into 10 to the power of 4 category ok so how do i do that let me keep this number as it is 6.1 into 10 power 4 so i am converting this number 2.2 into 10 to the power of 3 i am converting this exponent in the form of 10 to the power of 4 so how do i do that if i shift this decimal point here so how can i write the number i can write it as 0.22 into 10 to the power of 4 isn't it say when i write it as 0.22 how i can write say one unit i have moved towards the left side so it will be 10 to the power of 1 into 10 to the power of 3 is there so i can write it as 0.22 into ah 3 plus 1 4 10 to the power of 4 like that i converted this number in the format of 10 to the power of 4 so this is very very important guys when you are adding and subtracting two numbers see that the exponents must be there in same number if not same number convert any one and make it equal okay fine but now rest of the thing is same so you will be doing 6.1 plus 0.22 okay and now 10 to the power of 4 is a common that you will be taking it as outside so 10 to the power of 4 10 to the power of 4 i'm taking it as a common now just 6.1 plus 0.22 is how much it will be 6.32 into 10 to the power of 4 is your answer that's it right so main thing is see that the exponent are in same number if not in same number at least bring any one to become equal to the the other number other exponent okay so this is one example and now we will see uh subtraction subtraction of number so how do you do okay let me take it as a 4 into 10 to the power of minus 2 subtract with you know 2 into 10 to the power of minus 3 so what will i do you see the exponent here is 10 to the power of minus 2 here the exponent is 10 to the power of minus 3 so make it equal first make the exponent become equal so how do you make the exponent become equal okay so let me write this number as 0.2 so when initially 2.0 it is so this decimal when i bring it here it will be 0.2 uh one digit left side i have done so it is 10 to the power of 1 into 10 to the power of minus 3 so this one would be 0.2 into 10 to the power of 1 plus minus 3 that would be 10 to the power of minus 2 isn't it so now i am writing it as 4 into 4 into 10 to the power of minus 2 subtract with into 10 to the power of minus 2 right so what you have to do 4 minus 0.2 and 10 to the power of minus 2 i'm taking it as a common outside so 4 minus 0.2 is it will be 3.8 into 10 to the power of minus 2 is your answer okay so this is how you have to do addition and subtraction when the numbers are in scientific notation see that the exponent must be there in a same number if not in a same number convert any one and make the exponent same number and that exponent thing take it as a common and remaining digits you do addition or subtraction whatever they ask you here and this is all about scientific notation so you must be careful with how you convert the digits into scientific notation and also uh like how to do multiplication division subtraction and addition when the numbers are in scientific notation clear so with this i am completing this video and in my next video i will come up with a topic called significant figures which is also very very important from this chapter clear thank you so much and do subscribe our channel to learn the concepts in the easiest way and in a detailed way