[Music] hey everyone welcome to homeschool and welcome to class 11 series chemistry uh see we have already done a video on class 11 chapters overview where i explained about what are the chapters that is there in class 11 chemistry and a brief introduction about them isn't it and this is the video on the very first chapter that is basic concepts of chemistry so here first of all let us deal with what is actually the chemistry is and what is the importance of chemistry in everyday life clear so if i ask you to define the chemistry how do you define a chemistry see many of them who tell chemistry is the study of elements right and we have so-called elements in our nature right now 120 elements and they are beautifully arranged in the form of a table called periodic table we all know the basics of periodic table that we have learnt in class 10 isn't it see according to that people who think that it is the study of those elements not only the study of those elements and you know these elements what do they do the elements would combine with each other to form molecules and compounds isn't it say for example you have one oxygen atom would combine with another oxygen atom you would get oxygen molecule or you have hydrogen molecule itself that would combine with oxygen molecule and you may get a new compound called h2o right see these are the elements they are combining to give molecules so chemistry is not only the study of these elements that is very nicely arranged in a periodic table it is also the study of these molecules it is the study that involves how these atoms or elements have combined to give molecules and it is the study of those molecules their properties their structure their chemical nature and everything right say chemistry is the study of infinite molecules and you don't have limited number of molecules in our nature you have infinite endless countless number of molecules so it is the study of all those molecules nature structure composition and what not it is everything right and where are these molecules or compounds or elements present they are present in the matter itself right so what do you mean by matter this is not a new word for you say matter is anything in the universe uh that occupies space isn't it occupies space and has some mass such a thing is called matter are we matter definitely we are matters and this chalk piece is a matter air is a matter everything is a matter because if you take this chalk piece it has certain mass and it is occupying some space in this universe so i can call this chalk piece as a matter like that if you see all living things that you see from your eye and non-living things that you see from your eye everything is a matter right so i will redefine chemistry now here i can define chemistry as it is the study of study of structure composition and properties of matter here so this becomes a perfect definition for chemistry it's not only the study of elements it is the study of that infinite countless number of molecules and where are these countless number of molecules and these elements present definitely in so-called matter so they are present in everything that we see from your from our eyes isn't it so ultimately i can say study of structure composition and properties of matter is called chemistry isn't it say and now can you able to tell me what is the importance of chemistry why do we need to study this branch of science and this branch of science is dependent on other branches of size you know all the branches of signs are interconnected with each other what are the different branches of science physics is a branch biology is a branch chemistry is a branch right so these are all various branches of science and they are all interdependent one branch is dependent on another right and you know what what do you mean by biology biology is a study of life biology is a study of human body organisms body plants body and what does the body contain any living organisms body contain the chemicals the so it's a matter right so it contains lots of elements lots of compounds and too many chemical reactions are taking place inside the body right say here also chemistry is involved so there is no biology without any chemistry and there is no chemistry without any biology right so similarly even our physics is dependent on chemistry chemistry is dependent on physics so all these branches are interconnected interdependent with each other okay so now what is the importance of studying chemistry in everyday life phase we see chemicals everywhere right we eat chemicals the food we eat is a chemical only right and the water we drink is a chemical only like that if we see morning soon after we get up until we go to the bed we are connected with so-called chemicals all around they may be natural they may be artificial chemicals right but definitely we depend on chemicals right and let us see some examples chemicals are widely used in the field of medicine right see nowadays every disease can be cured with the help of medicine and this medicine is nothing but chemicals they these chemicals are prepared by various other reactions i can say and you know two such chemicals i will mention here they are very very important there is a chemical called cis plating these are the things mentioned in your ncip books so i'm mentioning here cis platinum and another uh medicine called taxol so these are the two medicines which are used in cancer therapy so to cure a cancer we use certain chemicals they give treatment with the help of chemicals called chemotherapy so in chemotherapy cisplatin and taxol are the chemicals which are used right and also there is another chemical called acetothymidine azido thymidine and this is the chemical which is used uh for aids patients used for aids patients say uh likewise if we go on mentioning the chemicals you know the parasite we take when we get a fever analogistics that we take as pain killers you know all these are various chemicals only right so chemicals play a lot of importance in the field of medicine and now i can say chemicals in food chemicals in food even in the food industry the preservatives that we use preservatives that means uh using this we can store food for a longer time uh they are called as preservatives and we can use food colors right so various other things we use in the food industry also and the chemicals in agriculture say agriculture uh nowadays too many different types of farmings are available natural or artificial chemical usage farming whatever it is the chemicals are widely used so chemicals are used in the form of pesticides right insecticides and what not you can use them as fertilizers right so in a different way it can be used even in the agriculture right like that if we go on mentioning there are various industries textile industry paint industry uh you know every industry uh chemicals are used and now we have lots of uses with different types of chemicals at the same time we have so many side effects of using chemicals also say for example chlorofluorocarbons that we use in the refrigerators cause you know ozone layer depletion isn't it and likewise the gases like sulphur dioxide nitrogen dioxide uh these are the gases that come out from the factories even they cause the air pollution you know they are responsible for acid rain likewise if we go on telling the dangerous aspects of chemicals numerous numerous things are there say one point i would like to tell you is yes we use chemicals for the benefit of man at the same time we have to limit the usage of artificially synthesized chemicals because they are more dangerous to the environment so we have to use them in a limited way otherwise it would destroy uh the well-being of mankind right so chemicals has both benefits as well as uh hazardous things also so this point we have to keep it in a mind and then a proper usage of chemicals may give enough benefit to a man but when you overuse it it could destroy the well-being of man isn't it so this is some introduction about uh the chemistry and the importance of chemicals and dangerous aspects of chemicals and now without wasting much time let me move on to the next concept that is nature of matter because chemistry is all about the study of matter isn't it so let us see what are the different types of matter i mean matter can again be classified into so many types and let us see what are those types and what is their nature see guys based on the physical state matter can be classified into three categories one is solids liquids and gases isn't it this way of classification we have learned it in our earlier classes also so this classification is mainly based on physical state of matter physical state clear okay so now what do you mean by solid say this chalk piece is a solid board is a solid say solids are a type of a matter which have definite shape and size so they have definite shape and size isn't it and you know uh in a solid the atoms are arranged in a closely packed fashion i mean between one atom and another atom or these guys may be molecules see matter is made up of atoms or molecules so it may be an atom or it may be a molecule of matter between the molecules or atoms you have lots of attraction between them okay so that is the property of solids clear that is the reason they have a proper shape and a proper size okay and coming to the liquids and liquids do not have a definite shape no definite shape but they have volume they have so called volume okay and in a liquid uh whatever the atoms are molecules present in the liquid matter they can move they have a ability of moving it's because you know the atoms or a molecules would have a space between them that's the reason there is no much attractions between the atoms and molecules of liquids that's the reason they can freely move whereas in the solid there is no movement of atoms and molecules okay fine and what do you mean by a gases say oxygen gas hydrogen gas which are present in the atmosphere uh what do they have they do not have any shape and no shape no size also clear and you know if you see the atoms or molecules in a gas you can see lots of spaces are there in between and there are no much attractions between the atoms or molecules so they can very nicely move in a random way isn't it and you can see the atoms and molecules of solid how i have shown you it is there's no gap between them and they are closely packed uh that's the reason they have a particular shape and they can't move and here these guys have little attractions and uh you know they have little spaces between each other and they are free to move and here uh the freedom of movement is too much they can move very nicely in a random way say this is some basic aspects about solids liquids and gases clear fine and now the matter can also be classified uh into you know mixture and pure substance clear there is another classification of matter that we have already studied in our previous classes it been can be classified as mixture and pure substance and now let us discuss what do you mean by a mixture and mixture is nothing but a combination of combination of two or more substances substances is nothing but any kind of a matter if two or three types of matter is mixed together then we call it as mixture okay and you know they have been combined in any ratio in any ratio okay they they there is no fixed ratio for the mixture say for example if i say sugar in water sugar in water when i put a spoon of sugar in water it becomes a mixture sugar is one type of matter water is another type of matter this is one substance this is another substance and i'm combining both of them so i can call this as a mixture now okay and you can mix these things in any ratio right so you can add one spoon of sugar in one liter of water or you can add once one spoon of water in so much amount of sugar you know there's no perfect ratio like this much amount of sugar has to be combined in this much amount of water right so you can mix these things in any proportion in any ratio then you will normally call it as mixture okay and now what do you mean by a pure substance you know pure substance is a pure chemical substance where two substances i mean two different patterns can be combined but with a fixed ratio so here you have a fixed ratio okay say for example water water is called as a pure substance okay you you can ask me like it's a combination of hydrogen and oxygen no ma'am how you will call it as a pure substance i have to call this as a mixture no you know this is a doubt you will get but you see how is water formed water has formed by the combination of two atoms of oxygen with one atom of oxygen isn't it so only then water is formed when two hydrogen atoms would combine with one oxygen atom only then water is formed that means they are combining in a fixed ratio they are not combining in how many how much ever they want however they want isn't it say when the two different matters they this is one element this is an another element both are matters only but combining in a fixed ratio so water is called as a pure substance and sodium metal is called as a pure substance oxygen gas is a pure substance right a single element or it may be a molecule or compound but if it is combined in a fixed ratio then we can call it as a pure substance clear fine and now coming to the mixture mixture is again classified into two types one is homogeneous mixture and other one is heterogeneous mixture right okay so what do you mean by homogeneous mixture here the composition is uniform throughout composition is uniform what do you mean by composition is uniform here say okay let me give one example first sugar water sugar water or salt water is the example and let me give an example here heterogeneous heterogeneous in the sense composition composition is not uniform observe the example sand sand plus water imagine if you put a one spoon of sand in a beaker of water will you have sand particles throughout the water no right all the sand would go at the bottom and they would settle i mean sand is there only at the bottom of the water what about the top surface of water it is pure it's only a water there will not be any sand that means in entire water the sand particles are not present right they they are restricted to one particular area in water medium isn't it so that's what we mean by heterogeneous that's what we mean by composition is not uniform that means sand particles are not present all through the water right they are restricted to one particular place they went to the bottom and they got settled isn't it but if you put one spoon of sugar in water and nicely when you mix it what happens you will have sugar particles throughout the water at the bottom of the water you have sugar plus water on the surface of the water also you have sugar particles in the middle of the beaker also you have sugar particles isn't it so sugar particles are spread evenly uniformly throughout the water right that such a mixture we will call it as homogeneous here everyone that's all and now pure substance is again classified into element and compound okay now what do you mean by element element are those substances which are made up of with same particles they are made up of with same particles so what do you mean by the element is the pure substance made up of same particles if you take up iron rod okay say at every corner of this particular iron rod you have the same particles called iron atoms so this iron rod would have cross of iron atoms but all are iodine atoms only you don't find any other atom in between right say such a substance such a pure substance which is made up of same particles here the particle is atom isn't it so matter is made up of atoms and molecules matter is made up of molecules molecules is again formed by the combination of atoms so ultimately what is the smallest particle of matter atoms so if a pure substance is made up of same type of particles then we call it as element so what do you mean by compound compound means made up of different particles compound is a pure substance made up of different particles say for example water here okay so water is pure one but it is made up of two different elements that is hydrogen and oxygen isn't it so this is some basic introduction about how matter is classified based on the physical state we can classify this into solids liquids and gases and based on the general way i can classify matter into mixture impure substance mixture is again into homogeneous mixture and heterogeneous mixture pure substance is again into element and compound so this is all about nature of matter so in my next video we will discuss about the properties of mata okay meet up in the next session till then take care and do subscribe our channel to learn the concepts in the easiest way thank you so much