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Current time:0:00Total duration:10:14

Video transcript

when this red color solution mixes with this liquid its color changes to blue and you might be wondering that hey what kind of magic is this but no this is just a chemical reaction see this red color solution is a litmus and when it comes in contact with a base its color changes to blue so let's talk more about litmus so see litmus is a dye meaning a colored substance we use dyes to color various things like to color our food to color our hair and to even color clothes right so let mmus is a dye and we derived this from lichens lichens they're a combination of algae and fungus okay don't worry about them basically lichens are some organisms from which we derived this dye called litmus which can change its color when it comes in contact with an acid or a base and therefore this can help us identify an acidic solution and a basic solution now you might be wondering rum why do I need this so see so far we know that acids tastes are for example lemons or oranges they both have acids in them and they taste sir whereas bases they taste bitter for example bitter good or spinach or any green leafy vegetable they all taste bitter and they all have bases in them but see we can't go around tasting each and every solution to identify for acid and bases because he some acids and bases could be poisonous to us harmful to us right so for this purpose we cannot rely on taste itself and that's why we use indicators see indicators are compounds that indicate to us or tell us whether a given solution is acidic or basic see when an indicator comes in contact with an acid or a base it will either change its color or it will change its smell to let us know and you know litmus is a type of indicator that changes its color by the way there are many more indicators apart from litmus also but we will talk about them in a separate video in this video we are only going to talk about let syndicator okay so now let's look at an experiment and see how litmus changes its color in the presence of acid and base now generally you would find litmus solution to be available in two colors one would be blue in color and it will be called blue litmus solution and the other would be red in color and that would be called red litmus solution now let's see how these change color so here I have an acid in a container and I'm going to add a blue litmus solution to it okay so you can see that slowly the color is changing to red okay this means that whenever an acid comes in contact with a blue litmus solution the color changes to red means in case of an acid the color will change from blue to red now here I have a base and I'm going to add a red litmus solution to it now you can see that slowly and slowly the color is changing to blue that means when a base comes in contact with a red litmus the color changes to blue that means a base changes the color from red to blue and this is how litmus helps us identify a solution as an acid or a base now imagine if you have an unknown solution and you want to find out what it is so you put a blue litmus into it and you see the color is changing to red that means it's for sure an acid because our system is the color of blue litmus to red and if you had put a red litmus and you saw that the color was singing to blue then for sure you know that this is a base because base changes a red litmus to blue okay now you might be thinking now this is getting slightly complicated to remember there's so many colors blue to red and red to blue how do I remember this so see for this purpose I use the mnemonic B to be meaning bases to blue or bases T in the color from red to blue okay or you can use a mnemonic B RB meaning bases turn red to blue and you know once you remember the color change for base the color change for acid is going to be just the opposite if base is turn red to blue the NASA's returned blue to red and I this every time to find out what the color change is going to be okay you might be wondering that rum acids turn blue litmus to red okay but what would happen if I add a red litmus to acid will there be any color change and if yes then what will the color change to so okay why don't you pause the video and think about this yourself first now if you have tried it let's see see as it's turned the color of blue litmus to red but if you add a red litmus to it the color will remain red there would be no color change that you will notice over here and similarly base has turned the color of red litmus to blue but if you add blue litmus to a base the the color will remain blue there would be no color change that you will notice over here also okay to convince this to you I have another experiment see lemons have acid in them and we know that acids turn blue litmus to red so when I add lemon juice to blue litmus you can see that color is singing to red but if I add the same lemon juice to a red litmus solution see the solution remains red we cannot see any color change happening over here right so so far we have seen how litmus changes its color when it comes in contact with an acid or a base but what about solutions which are neither acidic nor basic for example water sea water is a neutral solution can you guess what will be the color change of litmus when it comes in contact with water pause the video and take a guess now if you have tried it let's see so instead of telling you let me just show you the experiment so here I have two containers of water and I'm going to add litmus to each one of them okay so first I'm adding a red litmus to the first container and you can see that the color remains red the color is not changing at all okay now let's try the same thing with blue litmus I'm adding the blue one to the second container and you can see that the color remains same over here also the color is not changing now this means that litmus when comes in contact with a neutral solution it does not change its color the red litmus will remain red and the blue litmus remain blue in color so so far we have seen that acids turn blue litmus to red in color and if you had a red litmus to them they will remain red in color there will be no change happening and on the opposite basis turn red litmus to blue in color and if you had blue litmus to bases they will remain blue in color and there will be no color change that you will notice here and if you have a neutral solution then there will be no color change happening if you add blue litmus to it it will remain blue and if you add a red litmus to this it will remain red and how I like to remember this is by using the mnemonic b2b basis turn to blue or BRB basis turn red to blue basis done red to blue okay now with this I would like to ask one question I'm given that on adding blue litmus to a solution no color change is observed what can the solution be now the options are acid-base and neutral so over here I want you to pause the video and think about it and see this question is slightly tricky so take your time so okay now if you have tried it let's see so here we have been given that when we add blue litmus to this solution there is no color change that we observe so see this solution can definitely be neutral because you know when you add blue Ritt masoor red litmus to neutral there is no color change that we see right but it can also be a base see we have seen that basis turn red litmus to blue and if we add blue litmus to a base then it remains blue we do not see any color change happening over there same thing is happening over here when we are adding blue litmus we are seeing that it is remaining blue there is no color change right so this solution can also be a base so we cannot be sure that whether it is a base or a neutral solution and to be sure we will have to test this with a red litmus solution now imagine if red litmus solution that also does not show any color change that means for sure this solution is neutral but if this changed from red to blue that means definitely it is a base not neutral right now one last thing about litmus see some of you might have litmus paper in your lab instead of litmus solution basically it is just paper dipped in litmus solution if you dip a paper in red litmus solution you'll get a red litmus paper and if you dip it in blue litmus solution you'll get blue litmus paper you know litmus paper are very handy and easy to carry and that's why we often use litmus paper instead of litmus solution but the chemical reactions and the color changes that happen are exactly the same if you put a red litmus paper in a base the color will change to blue and if you put a blue litmus paper in an acid the color will change to red now let's summarize the video in this video we saw that litmus is a type of indicator that indicates us the presence of acid or a base by changing its color and it is generally available in two colors red and blue and you should remember that raychel it must changes to what color when it comes in contact with acid and a base and we also spoke about how to remember this by using the mnemonic B - B or B R B and if you forgot about these things don't worry you can go back and watch the video and recall these things