Exploring substances : Acidic, Basic and neutral/7th science/complete explanation

[00:00:00]Hello everyone, welcome to our YouTube channel Curious Minds Canada. This is your science facilitator Puja. So today in this video we are going to learn about a very interesting chapter of seven standard that is exploring substances acidic, basic and neutral. So this is a seventh standard chapter and it is second chapter. Let us see whatever the topics are covered in this chapter. Along with that we will learn each and every topics along with the interesting activities. So let us start the chapter. So they have started the chapter or the lesson with a interesting story actually uh which is based on like on February 28th. You all know that what is a speciality of February 28th? It is science day correct? So the school hosted a science fair to celebrate national science day. At the entry gate, siblings Ashwin and Ki were greeted with a white sheet of paper. Fine. You know that when somebody uh goes to any of the function, they are going to greet them with flour or with some greeting. But here uh they greeted with a white sheet of paper. Nothing was written on that.

[00:01:14]They were curious to know why a white sheet of paper was given to them.

[00:01:19]Correct? They were very curious. They wanted to know why they have given us the white sheet. A few steps ahead there was a volunteer spare spraying a liquid on these sheets of paper. So when they moved a little bit forward uh there were standing few students were standing and they were spraying some of the liquid on it. The siblings also got their white sheet sprayed. So this Ashwin and Ki who were carrying the white sheet, they also got their paper sprayed. So they sprayed some liquid on it. To their surprise, the words welcome to the wonderful world of science appeared on the papers. The moment the liquid was sprayed, when they sprayed that liquid, the welcome uh words whatever they were written was started to see. They were excited and eager to know how this happened and the reason behind it. So they were so excited and also they wanted to know that how this magic has happened. Their curiosity was partly satisfied at the colorful world of substance stall. So uh as you know that when there is a science fair there will be some stalls which will be there and few of the activities will be done over there. Correct? So when they move to the colorful world of substance stall there their curiosity was getting satisfied. That means they were coming to know more answers about such questions. They saw many activities showing color changes on mixing different substances. So when two or more different substances were mixed, they were seeing that many of the or the chemical colors were getting changed.

[00:02:59]They decided to explore these changes further. Let us join them on this uh learning adventure. So what they decided is they decided that even we want to learn more about these chemical substances or changing why they are changing how they are changing. So they wanted to know more about this. So let us join Ki and Ashwin along with them.

[00:03:22]Let us also learn about more chemicals or more substances. Okay. So whatever they told here we will perform that activity also in the further activities. Okay, it is a classic science. So here we will see the answer why on the white paper when they sprayed something they got the letters to see or it became visible. How that happened that we will see here.

[00:03:51]It's a classic science magic trick that release on a chemical reaction between an indicator and a base. So one will be the base and one will be the indicator.

[00:04:03]So whatever they had written that was from a base. Okay. So what is base that we will learn in this chapter further and also what they have sprayed that was an indicator. Here is a breakdown of how Ashwin and Ki saw those hidden words appear. Let us see how they saw this.

[00:04:21]Okay. The secret ink. Before the siblings arrived, the words were written on the white paper using a colorless substance. The most common colorless substance uh usually I mean whatever they had used correct. So on the white paper first they did not see any of the words correct. So that should be written from something else that most common choice for this is phenopylene. So this is an indicator correct. What is indicator that we will learn afterwards. Then in neutral or acidic state phenopylene is completely colorless. So it looks like plain water or white paper. Once it dries the paper looks empty. So when phenopylene indicator it gets dried completely the paper looks as it is like it nothing has been written on it. The reaction when an alkaline basic solution touches it a chemical change occurs that alters the way of molecules reflect light turning them a bright pink or magenta color.

[00:05:27]So here the magic spray or the liquid whatever they may used that may be a base usually it is sodium hydroxide solution it was a dilute solution when they sprayed it so the pinylene reacted with this base and it gave a color of pink or magenta color let us see activity here 2.1 nature our science laboratory Three litmus as an indicator activity 2.1 let us explore collect some samples of so here they have told to collect few of the samples like lemon juice soap solution amla juice tamarind water vinegar baking soda etc etc take a strip of blue litmus paper and cut into small pieces you have to take blue litmus paper anyway you will watch that activity spread these pieces on a clean and dry white tile using a dropper. Put one drop of each of the sample and you have to see what the color is going to change. Okay. Anyway, we will do that activity and we will see what it's going to happen.

[00:06:42]Now we will see the activities which are given in your textbook and the first activity is to find whether the things which they have listed are acidic or basic. That means will they change the color of litmus paper or not? So we have two types of litmus paper. One is blue litmus paper which is blue in color and the other is red litmus paper which is in red color. Okay. And we have taken the items which they have given in your textbook that is uh lime juice, soap solution, tamarind solution, vinegar, baking soda solution, then lime water, tap water, washing powder solution, sugar solution and salt solution. So in this we will check whether will they change the color of the litmus paper or not. Okay we will start with the lime juice. A simple thing is we have to take a drop of it and we should place it on the litmus paper. Okay just observe whether it will change any color of it or not. See can you change? Can you see the change here? The blue litmus paper have changed its colors to the red. Now we will take the soap solution and we will check. Okay, here and here it also have changed its color but it is very light that you are not able to see now. Afterwards you can observe it. We will see the tamarind solution.

[00:08:02]See how fastly it changed the color again to the red. Then we will check for the vinegar.

[00:08:10]Can you see it changed its color. Now we will take the baking soda. You can see it has changed to the red has been changed to the blue. Now lime water.

[00:08:28]See the red paper has changed to blue color.

[00:08:32]It is normal tap water.

[00:08:35]Here we will not see any changes in the paper color. This is washing powder solution and it has been changed to blue. This is sugar solution and this is salt solution.

[00:08:55]So in sugar solution and salt solution and tap water we will not see any changes in blue litmos paper or in the red litmos paper. We can see the changes in the blue to red. We can see it in lime juice. See the blue has changed to red here and even in the tamarind water, vinegar.

[00:09:17]See, and such things or such solutions which turn blue litmos to red are called as acidic in nature. And there are many things which will turn uh red litmus paper to blue such as soap water and here the baking soda solution, lime water and washing powder solution. They have clearly changed their color from red to blue as you can see here. See it was a red litmus paper but it clearly turned it to blue color. Right? And such solutions are called as basic in nature.

[00:09:52]And few like tap water, sugar water and salt water. They will not turn any of the litmus color. So they are neutral in nature.

[00:10:01]I hope you enjoyed the activity. So you saw how the litmus paper was changing its color. So you observed it and you have to record that observation in the table 2.1 which is given over in your textbook. Repeat the same activity with the pieces of litmus paper which is red.

[00:10:19]Okay. Now you saw the activity with blue litmus paper. You have to see the activity with the red litmus paper also.

[00:10:25]And record your observation in table 2.1. So both red litmus paper and blue litmus paper. Whatever you saw the activity with both the litmus paper that you have to record in the table. Then how to prepare lime water? There they have given that you have to take lime water and do the activity. Correct? So how to prepare that lime water? Let us see what it is. Don't get confused with the lime water with the word lime. Okay?

[00:10:55]Don't confuse it. Lime water is not not the lemon water. Fine. Which is a fruit similar to lemon. Lime water. It is nothing but the solution of calcium hydroxide in water. can be easily prepared by mixing lime fine it is a tuna or you will call it as sunna correct in water and leaving it undisturbed for some time. So you have to take chuna or lime or sunna you have to add water to it and you have to leave it undisturbed. That means you should not disturb it and you should leave it for some time. If possible leave it for overnight, one full night. filter the liquid into another container and use it as lime. Then you have just the water which will be present on the top of it.

[00:11:42]You should take it on one container and you should use it as lime water that you can see it in the picture also. Correct?

[00:11:50]If you leave it for some time it the topmost layer will become colorless there. Table 2.1 testing the nature of samples with blue and red litmus paper.

[00:12:03]This activity we have already done it.

[00:12:05]Here is the table which is given for you. Okay. First one is lemon juice.

[00:12:10]Color of blue litmus paper will turn red. But the red litmus paper it will not change any of its color. That means it will remain as red. Soap solution blue litmus paper will remain as blue but red litmus paper will change as blue. Amla juice turns red, red litmus paper will remain as red. Tamarind water will turn red but the red litmus paper is going to remain as red. Vinegar again blue litmus paper will turn red but red litmus paper remains red. Baking soda solution here the blue litmus paper remained as blue but red litmus paper turned into blue. Lime water, blue litmus paper will be in blue color but red litmus paper will become blue. Tap water red litmus paper also will be in red in color. Blue litmus paper will also not change its color. It will be in blue. Washing powder solution blue litmus paper will be in blue but red will turn into blue. Sugar solution both bluemas paper and red mitten paper will be in the same color. It will not change even in the salt solution. So here some of the solutions will turn the blue litmos paper to red, some of will turn red litmus paper to blue and some will not turn either blue or uh red litmus paper to any other color. So we have to classify the things. It should be based on something right. Let us see what it is.

[00:13:42]Now let us analyze table 2.1 and sort the samples into three groups as follows. Group A with samples that turn blue red uh blue litmos paper to red. So there will be one group in which the blue litmos paper turned into red. Group B with the samples that turn red litmos paper to blue. Group C with the samples that do not affect either of two litmus paper that means uh either blue litmos paper did not change its color even the red litmus paper did not change its color. Record the data in table 2.2. So we have to again write that in another table. Grouping the samples tested in table 2.1. You have to enter it. Using the results above we can sort them into three required groups. Let us see what it is. Group A, lemon juice, amla juice, tamarind vinegar. Group B that means red to blue. Soap solution, baking soda, lime water, washing powder. group C that means there is no color change even in uh blue or in red that is tap water sugar solution and salt solution so why it is so let us see so before that let us see about the litmus I'm telling about litmus paper blue litmus paper red litmus paper so before knowing what it is correct so we have done all this experiment so let us learn what is the litmus paper actually it is I am curious to know what are these Red and blue litmus paper strips made of what they are made of. Why do they change color when drops of some samples are put on them? Correct. So first we should know what they are made up of and then why they will change its color when some of the samples are put into it. So you can see the pictures of litmos paper over there. It is blue and red litmos paper. Let us find out that litmus is a natural substance obtained from lichins. You can see the picture of lichins. From that lichens we will get this litmus paper.

[00:15:48]Liens are formed by the association of two living organism. A fungus and an alga. That means one fungus and alga join or combine together or associate together and leave together that we will call it as lichins. They grow on rocks and trees in region that have abundant rainfall and clean air.

[00:16:09]That means where there is no air pollution you can see the white patches and they are called as lichens. Do you find lichens on trees in your neighborhood? So you can see uh the lichens which are grown on the rock. Can you see any of the lichens on the trees or the rocks of your surrounding? That means your surrounding or the environment which you are living is very clean. That means there is no air pollution around you.

[00:16:40]It is available both as solution and in the form of paper strip known as litmus paper. So from luchin we will get the litmus. Litmas will be available in solution form and also in the strip form which we will call it as litmus paper which we use to do the activity. The litmus paper is available in two colors which are there blue and red. You have already seen it. Substances that turn blue litmos paper to red are acidic in nature. That you have to remember. If blue litmus paper turns to red, it is acidic. Easy to remember. If it turns red, red is red is danger color.

[00:17:19]Correct? And acid is also danger. When something blue litmus paper, if it is changing to red, it is acidic. Red is danger. Acid is also danger. So you can remember like that. While those that turn red litmus paper to blue, it is called as base.

[00:17:39]You can see that in the picture.

[00:17:43]Since litmus shows different colors in acidic and basic solution, it is called as an acid base indicator. So it shows uh whether the solution is acidic or basic in nature. Correct? That's why it is called as acid base indicator.

[00:18:00]Classification table. Now group A that is acidic. Lemon juice, amla juice, tamarind juice and vinegar. These turn blue litmus paper to red. Red is danger.

[00:18:12]Danger is acid. So they are acidic in nature. This implies the substance are acidic in nature. Group B, soap solution, baking soda solution, lime water and washing powder solution. These turned red litmus paper to blue.

[00:18:28]Correct? So this indicates that substances are basic in nature. Group C, they are neutral. Tap water, sugar solution, salt solution. So they did not change any of the litmus paper. Blue also didn't turn into red. Red also didn't turn into blue. That means there is no change. And such substance we will call it as neutral. They are not acidic.

[00:18:49]They are not basic. They are in the middle. That is they are neutral.

[00:18:55]Activity again 2.2. Let us relate and explore.

[00:19:00]Are all the substance in group A and of the table 2.2 are edible? Edible means what? Can we eat it?

[00:19:09]Have you ever tasted these edible substances? Can you recall their taste?

[00:19:15]So now I told in group A, lime juice, lemon. What is the taste of lemon? Is it sweet?

[00:19:25]It is sore. Correct.

[00:19:27]Tamarind juice. Tamarind is also sore.

[00:19:31]Correct.

[00:19:33][cough] Edibel means which can be eaten. The substances which you ate and you felt it sore. Correct? Usually we will tell it as they are acids or acidic in nature.

[00:19:47]You will find that all these substance taste sore. Thus we can say that substances that taste sore tend to contain acids and they are acidic in nature.

[00:20:01]Next caution do not taste anything until asked to do so. Mom has told to taste.

[00:20:07]So don't go and taste everything which you get. No. Until you are said to taste something, don't do it. Do not taste any unknown substance. Whenever the substance is not known for you, please don't go and eat it.

[00:20:23]Some common edible substances that means eatable substances and the names of most common acids present in them are given here. So they have given a table. Orange it contains citric acid. Amla ascorbic acid and citric acid. Raw mango tartaric acid. Tomato citric acid and oxylic acid.

[00:20:47]So these are the common acids which are present in the edible substance that means which are eatable activity.

[00:20:53]Identify the acids. Now you have to identify the acids. Fine. Find out and write the names of most common acids present in the following substance. I have already given. Lemon contains citric acid. Curd contains lactic acid.

[00:21:08]Tamarind consists of tartaric acid.

[00:21:11]Vinegar consist of acetic acid. So you have to know some of the acids name which are very common like citric acid, lactic uh then tartaric acid, ascorbic acid, oxylic acid. So all these common names you should know.

[00:21:27]Now we will see about the properties of bases. So now you got to know two properties of acids. What is the one?

[00:21:34]First thing it turns blue litmus paper to red. Second it tastes sore. So now we will see the properties of bases.

[00:21:44]Now let us take one of the substance okay baking soda solution from group B.

[00:21:50]So we will take the baking soda solution which you have already done the activity. Rub the baking soda solution between your fingers. What do you observe? So you have to do that activity right? Come let us do it. Here we will see how we will feel when we touch a base. I have taken baking soda and some amount of water here. What I'll do is I'll just take a pinch of baking soda and I'm going to add a drop of water to it. Okay.

[00:22:23]Just I will rub it between my fingers.

[00:22:27]Okay. And then I'll just washing in this water itself. Even though after washing you will feel that something is slippery that is present over your fingers. Okay.

[00:22:41]It feels so soapy and slippery. So you already came to know that basic uh sorry the baking soda is a basic in nature. So all the bases which are present will have this slippery or soapy feeling.

[00:22:56]Same it feels same as when you touch a soap. Okay. So with this we can conclude that always the basic solutions or basic substances will have the slippery or soapy feeling.

[00:23:10]Did you see how it actually felt when you took the baking soda solution and rubbed between your fingers? Yes, it feels soapy or slippery to touch. It will slip like a soap. Basic substance are generally slippery to touch. That means uh it will not be rough. It will be very slippery.

[00:23:30]Also, bases generally taste bitter. It will taste bitter. Please don't taste any of the soap, washing soda and all.

[00:23:39]It is just told that it will be bitter in taste. But everything that tastes bitter may not contain a base. For example, bitter guard. Correct? It it is bitter in taste but it is not basic in nature.

[00:23:57]there. Now I can check the nature of floor cleaning liquid using an indicator. So let us check the nature of floor cleaner. What is floor cleaner?

[00:24:09]The liquid which you will use to clean your floor. Okay. So some of it we are going to test it uh using the indicator.

[00:24:19]Come let us do it. Now we will see the basic or acidic nature of this floor cleaner. Floor cleaner is nothing but in your home whatever they will use to clean the floor that is the floor cleaner. I have taken it in this and what I'll do is I'll take one red litmus paper and I'll take one blue litmus paper and I'll just dip inside this floor cleaner.

[00:24:45]Okay.

[00:24:50]Yes. Can you see the difference? Now here the blue litmus paper has not at all changed its color. But you can observe this red litmus paper it completely became blue in color. With this we can conclude that the floor cleaner whatever you are using in your home is basic in nature.

[00:25:13]That was a very interesting activity.

[00:25:15]Right? Come on let's continue the chapter. If litmus is not available, are there some other natural substances that can serve as acid base indicator? Think that you don't have the litmus paper but you want to check whether an uh substance is acidic or basic in nature.

[00:25:32]Do we have anything in nature that we can use? Come, let us see it. Yes, there is a red rose as an indicator. You might have observed many colored flowers in your surroundings. Try making your indicators using these flowers. So uh using the red rows we can make that indicator. So let us see how to prepare it. Activity 2.3. Let us prepare.

[00:25:56]So you have to collect some of the fallen rose petals. Okay. Please don't pluck any of the flowers. Then you have to uh wash them. You have to crush it using the motor and pezle. And you have to keep it in a uh tumbler. You have to pour some uh hot water to it. Then ensure that crushed flour petals are completely immersed.

[00:26:19]Perform this under the supervision of an adult because you will take the hot water. Cover the glass tumbler with lid.

[00:26:27]Wait for 5 to 10 minutes till the water becomes colored and filter it. This is a very you know this filtrate is required a flour extract to be used as acid base indicator. This liquid can act as acid base indicator. So come let us prepare this indicator.

[00:27:10]It was very easy, right? To prepare the indicator. Yes. Now, activity again 2.4.

[00:27:17]Let us find out. Place 10 to 20 drops of prepared red rose extract in each of the two small transparent bottles or test tube. Mark them as A and B. Add 20 to 30 drops of lemon juice in test tube A and 20 to 30 drops of soap solution in test tube B with the help of a dropper. So, you have to take two tumblers. You have to add this rose indicator for that. For one test tube or tumbler you have to add rose water uh sorry lemon uh juice. For the other you have to add soap solution.

[00:27:51]Observe and record your color changes in uh table 2.3.

[00:27:56]So we cannot tell it now. Correct? We have to do it and see. Come let us see the activity. In this activity we will see how to prepare the rose rose extract and how we can use it as a acid base indicator. So to do that you have to take red rose petals. You have to crush it with water and pzle. You have to uh take it in a glass and you have to add boiling water or hot water and you can keep it closed for 10 to 15 minutes.

[00:28:26]Okay. Then you should take out the water which will look something like this.

[00:28:31]Okay. Okay, it will be pink in color.

[00:28:33]And uh to test few of the materials, I have taken tamarind solution, washing powder solution and salt water. With this, we will test how the rose extract is going to change the color of the things. So before doing that, I'll take the rose extract in each glass.

[00:28:57]Okay. Then we will add the solutions one by one. First I'll take this tamarind solution. I'll add it. See how it is going to change its color.

[00:29:08]Okay.

[00:29:10]You can clearly see we it has changed its color almost to red. Right now I'll take washing powder solution and I'll add it to this. See as soon as I add it, it became green in color. Correct? You can observe it clearly.

[00:29:31]Then I'll take this salt water and I'll add it to the solution of rose and mix it. But you cannot observe any of the change in its color. It remained as pink. So with this what we can uh observe is the rose extract can act as acid base indicator. It's going to change the color of the acid because you already know that tamarind solution is going to turn the blue litmus paper to red. So it is acidic in nature. So it changes the acids into red color. The basic solutions are going to take the color of green. It is very beautiful green, right? You can um see it clearly.

[00:30:14]And in neutral substances the rose extract will not change its color. It will remain as pink it is.

[00:30:22]So with this we can conclude that rose extract can be used as acid base indicator as it clearly distinguishes between acids, bases and also the neutral substances.

[00:30:35]Yes. Now let us see how to fill that table which is given in your textbook.

[00:30:42]Name of the sample lemon juice. Here the red rose extract will become dark pink or red. So nature of substance we can tell it as acidic in nature. Then soap solution it will completely turn into green we can tell it is basic. Amla juice it will become red. So it is acidic. Pure water whatever the rose extract you have taken that color remains the same. So we can tell it is neutral in nature. With this table what we can imply the red rose indicator in acidic solution it turns into dark pink or red.

[00:31:17]In basic solution it turns into green.

[00:31:20]In neutral solution it will not change its color. Correct? Yes. From the above activity we can conclude that the red rose extract can also be used to test the nature of substances. Hence it is another example of an acidic base indicator.

[00:31:37]We can conclude that the red rose extract seems to give red color in the acidic solution, green color in basic solution. So we can say that you may repeat the process of preparing extract and testing substance with some vegetables, fruits and flowers such as beetroot, per uh beetroot, purple cabbage, turmeric, Indian blackberry that is jamun and red hibiscus flour. They can also act as acid base indicator. Not only the rose petals but also these substances which they have given also acts as acidic basic indicator. You also try it once in your home and check it.

[00:32:19]Okay. Now fascinating facts.

[00:32:24]Hydrangeia is a plant that grows in cooler climates in Himalayan region and the northeastern states. You can see the flower over there. It gives flowers of different colors depending upon the nature of the soil. So whatever the soil nature is like if it is acidic, basic or neutral that changes the color [laughter] of the flower. Acidic soil produces blue colored flowers. Whereas in basic soil the flowers will be pink or red in color. So if it is more acidic, if the soil is more acidic it will give blue colored flour. If it is like basic then it gives pink or red color flour.

[00:33:02]Can gardeners alter the color of hydrogenia flowers by adjusting the acidic and basic nature of the soil completely. Yes. If you change the nature or the like uh um acidic or basic nature of soil, obviously you can also grow the different colored hydrogenia plant.

[00:33:22]Activity 2.5. Let us prepare. Take a spoonful of turmeric in a petri dish or container and add a little water to make a peso. You have to take a turmeric powder. You have to add water and you have to make paste of it. Then carefully dip a piece of filter paper in the turmeric paste until it gives yellow color. Take it out and allow it to dry.

[00:33:47]Cut these papers into small strips. It's called as turmeric paper. As the litmus paper is very small and thin, in the same way you have to prepare this also caution perform this step under the supervision of an adult. Again using a dropper again you have to put all the sample solutions which you used in activity 2.1 and you should see what the results it's going to give. So come let us prepare that.

[00:34:12]In this video we will see how to prepare the turmeric indicator and also how it reacts with the things. Okay. To uh make the indicator, what you have to do is you have to take the turmeric water solution and you have to just put it on this paper, white sheet paper. You have to leave it to dry.

[00:34:34]After it dries, you can just see like this you can cut and make into the strips. Fine. And this strips we will use it to check whether the given things are acidic or basic or neutral. And also we will see how it changes its color.

[00:34:55]Okay. Again we have taken the same solutions which I took in the first activity. First we will start with the lemon juice. Okay. I'll take a drop of it and I'll put on this paper. You can see there is no change in its color. Now I'll take this soap solution and put it on it. You can see how it changed its color to red. You can see here and compare it with this. Okay. I'll take tamarind water and I'll put it on this tamarind water itself is brown. So it may look that it's changing its color.

[00:35:32]Now if I wipe it like this, you can see it has not changed its color. Again I'll take a drop of vinegar. You can see there is no change in color. Then this is baking soda solution.

[00:35:49]You can see that it changed its color.

[00:35:52]This is lime water.

[00:35:56]And you can see that it changed its color. This is normal tap water.

[00:36:02]No change.

[00:36:05]This is washing soap powder solution. It change its color, sugar solution and salt solution. So you can see that there is no prominent color change in this.

[00:36:23]You can see how the color has changed to completely red here. Right? And also in baking soda and in soap solution. With this what we can conclude is whichever turned the blue litmus paper to red which were called as acids did not change color in this in this uh ter uh turmeric indicator. Right? But in the basic solution like soap water, lime water, baking soda solution and washing powder solution which changed red litmus paper color to blue. they changed the turmeric paper from yellow color to red color. So with this we can tell acidic solution will not change the color of the turmeric indicator. It remains as yellow but the basic solution will change its color to red or brown color and again the neutral solutions will not change its color.

[00:37:22]That was very interesting. Correct. Now we are seeing how we prepared it in the picture form.

[00:37:29]There table 2.4 Four testing the nature of samples with turmeric paper. We have to fill this correct. Lemon juice there is no change in the turmeric uh turmeric paper. So no change it is yellow color.

[00:37:41]Soap solution it turned into red color.

[00:37:44]Correct. Amla juice again it was in yellow. Baking soda it turned red or in reddish brown color. So with this we can tell turmeric in acidic uh region or acidic nature solution it will not change its color. But in basic nature solution, it will change its color to red or reddish brown.

[00:38:06]Yes, here see it is. I got a curry stain on my white shirt and on applying soap it change its color. Not only curry sambar. Okay. Uh even on many of the dresses you may get some uh turmeric stains. Correct. When you wash it with soap it turns to red or brown color. Did you come to know why it is? Because the washing powder or soap, you already read it. It is basic in nature. So, turmeric when reacts with the base, it's going to change its color to the red.

[00:38:41]You can see it over there. If you get a yellow curry stain on your cloths and rub it with soap, the stain turns red.

[00:38:49]This happens because soap is basic in nature.

[00:38:54]Can turmeric paper be used as an indicator for acidic substance? Actually for acids and neutral substance it shows same color yellow color. So it cannot differentiate between acidic and neutral substance. It will look like same. Based on observation we can conclude that turmeric paper can be used to test basic substance. However, it cannot differentiate between acidic and neutral substances.

[00:39:22]There fascinating facts.

[00:39:25]Why turmeric is is known as golden spice? It is called as golden spice. We have to know why it is correct. Come let us see. Turmeric is a member of ginger family which is grown in India and other countries. Turmeric is a family of ginger. A common spice in daily households. It is being researched for benefits beyond the taste and color it provides to the food. Correct. It is very healthy in the ayurvedic system of medicine. Turmeric is considered to have numerous health benefits and is commonly used for several traditional home remedies. So if you get any wound, your mom will tell just rub the turmeric into it. Correct? If you have cuff cold, what you will do? You will take uh hot water, you will mix some turmeric powder and drink it. Then you will your throat will feel so relaxed. So it has uh played a very important role in home remedies.

[00:40:19]So it is called as what? The golden spice. Yes. Let us continue. Now are there any substance whose order changes on adding acidic or basic substance? Now we saw when we add acidic or basic substance the color goes changing. Do you know any of the things which will change its order? The smell of it. It is interesting right? Let us see. There are some substances whose order changes in any of the acidic or basic medium. These are called as all factory indicators.

[00:40:50]Okay. They are known as all factory indic. All factory means what? Odor or smell.

[00:40:57]All factory indicators. These are the substances that change their smell like onion or vanilla. They are going to change when mixed with acidic or bases.

[00:41:09]Activity 2.6. Let us investigate. Take some finely chopped onions in a container along with some strips of clean cotton cloth of filter paper. So you have to cut onion in small pieces.

[00:41:22]You have to take it in a plate and add some of the filter paper so that water will get out of it. Tightly close the container and leave it overnight. So you have to leave that onion for whole night.

[00:41:34]Take two of the cotton cloth or filter paper strips from the container and check their order. Okay, you have to take out that cotton and uh you have to smell it and you have to keep it. Keep them on a clean surface and put some drops of tambarind water and on one strip and few drops of baking soda on the other. Allow the drops to spread on the strip. If you have taken cotton ball, you just wait till the cotton absorb the absorbs that drops of tamarind juice and also the baking soda solution. Then you have to check the order again. You have to check the smell of it. Do you notice any change in the order of it before and after putting the tambarine juice and baking soda solution on there? Note your observation. If you want to note it, we have to perform it.

[00:42:23]Come. So in this uh activity we will uh see how the oil factory indicator is going to say us whether a uh thing is acid or basic in nature. Till now we have seen the colors has been changed for the indicators. But now we will see how it is going to change with this all factor. All factor is nothing but the smell. So what you have to do is you have to take the pieces of onions and you have to put some of the cotton cloth into it and you have to leave it for overnight. Then you have to take three of the cotton cloths out of the onion.

[00:43:02]One will just act as a test because you have to see the smell. It it is the smell pungent smell of the onion. Now what I have to do is I have taken lemon juice and washing powder solution. First I'm going to add washing powder solution onto the cloth as you can see here. And I have I am adding the lemon juice on this cloth. You have to wait till the cotton cloth completely absorbs the solution. Then what you have to do is you have to take this cloth and you have to smell it.

[00:43:41]There is not at all any onion smell coming from this. That is the washing powder solution. I'll check this.

[00:43:50]There is a pungent smell of the onion.

[00:43:52]With this what we can conclude is from the basic solutions we can conclude the allactory or the onion smell has gone completely out. So the allactory uh indicators indicate that the basic solution will not have any strong pungent smell of onions but the uh acidic in acidic solution the allactory indicators will remain the pungent smell of it.

[00:44:21]Yes, even though you uh could not smell it obviously you cannot do it when I show it in video you can do it in your home correct. So similarly test the change in the order with other acidic and basic substance and record your observation in the table.

[00:44:38]Know a scientist they have given about a scientist. Let us see about him. Achara Profula Chandra is known as father of modern Indian chemistry. You can see the picture of him. He earned a doctorate in chemistry from United Kingdom and returned to India. He contributed towards advancing scientific research in India. He also established India's first pharmaceutical company in 1901. He was a person rooted in Indian culture and knowledge traditions.

[00:45:10]Through his writings on history of chemistry in India, he highlighted the achievements and expertised of ancient Indian scientists to the modern world.

[00:45:20]Rey a social reformer also advocated use of uh mother tongue as a medium of instruction in educational institution.

[00:45:28]So if your mother tong tongue is Canada or Hindi if they teach in that language obviously you will feel so you know involved you feel so curious and you will ask many more questions and get many more answers. Correct? So he instead insisted that you should teach the students in their mother tongue so that they will learn more about it.

[00:45:51]Okay. Next, what happens when acidic substance mix with basic substance? Now separately you studied what is acidic substance? What is basic substance? How you can differentiate between acidic and basic substance? But here what they have given is when you mix an acid with a base. Correct? When you mix it, what is going to happen?

[00:46:11]So here also they have given activity.

[00:46:13]Take one drop of lemon juice in test tube and add around 20 drops of water to it and observe the color. You have to observe the color of it. Add a drop of blue litmus solution to it. Do you observe any color change? If you add lemon juice and if you add some blue litmus solution obviously it's going to change into red.

[00:46:34]Correct. Slowly add drop of lime water to this test tube with the help of a dropper and swirl it. So for the same lemon juice you want to add lime water and you have to just mix it thoroughly.

[00:46:48]What do you observe? Is there any change in color of the solution? It is very interesting activity. Even though I don't have uh this um litmus solution, we will do this activity with a litmus paper. Come let us do it.

[00:47:04]Now we will see what happens if we mix acid and base together. Okay. I have taken uh lemon juice and also washing powder solution and a red litmus paper.

[00:47:15]First I'm going to add the washing powder solution at one end of this paper. You can see it has completely changed into blue color. Why?

[00:47:26]because washing uh powder solution is a basic and that's why it is going to change the red litmos paper to blue color. Now what I'll do is I'll just take a drop of lemon and add it over this. Okay, you can see that it is slowly changing its color again to red.

[00:47:49]Correct. Why is it so? Because when I have added the base, it turned into blue. But when I added acid to it, the basic nature has been cancelled by the acidic lime juice. That's why it changed its color to the red. Again, if I start adding this washing powder solution on it, it again changes back to blue when it takes a maximum amount. Why?

[00:48:21]Because it has to overcome the nature of acid and then it has to change to blue color. So it takes little amount of time. So this side you can observe that it is changing its color to blue. So with this we can tell that when there is a solution of acids and bases and when we start to mix it acid if it is acid and we add a drop of base the solution is going to become basic in nature. If it is in basic nature and if we keep on adding acids then it will turn back to acidic nature.

[00:48:59]You saw the changes right? So whenever you added blue litmus paper to the lime juice it became red. Again when you added lime water more it became again blue. Again when you added lime juice it became red. Correct? So this is how the acidic and basic substance when they are mixed are going to act. A stage comes when color of the solution changes from red to blue. Again add one drop of lemon juice above the solution. Can you predict why there is change in color?

[00:49:29]Because you you have already seen it.

[00:49:31]Correct? Lemon juice turns blue litmus to red because it is acidic in nature.

[00:49:38]But when you add one drop of lime water, it will become more basic in nature. So again it will turn back to blue color.

[00:49:46]Again when you add a drop of lemon juice it will acidic nature will increase. So again it will turn to red color based on the steps in activity 2.7. You are observing a neutralization reaction.

[00:50:00]When you mix an acid with a base they cancel each other out. So they are going to cancel each other out because both are same in proportion. Adding blue litmus to lemon juice, blue litmus solution turns red again. Reason because lemon is acidic. Adding lime water to red solution. As you add lime water drop by drop, the red color eventually disappears and turns back to blue. What is the reason for that? Because the lime water is basic in nature. It's going to react with acid. Uh when enough base is added, it neutralizes the acid. Okay?

[00:50:38]It's going to cancel out the acidic nature. Once the solution becomes slightly basic again the litmus is going to turn to blue again.

[00:50:49]Adding lemon juice again to the blue solution the solution will turn red once more because adding more acid it is going to shift the balance from basic to acidic.

[00:51:02]When an acidic solution is mixed with a basic solution, both solutions neutralize the effect of each other, this is called as neutralization reaction. That means both will be in equal state. It will not be in acidic, it will not be a basic. So it will be called as neutral state. The general equation is acid plus base which gives rise to salt plus water and heat.

[00:51:29]Then neutralization in daily life. Do you think that this acidic basic neutralization happens in our daily life and we use it? You may tell no but you will do it. Come let us see how. Okay.

[00:51:43]Situation one they have given in the form of stories. Kiti was observing a butterfly in the garden with her hand resting on a tree trunk. So she think that this is a tree trunk. She was keeping her hand like this and she was seeing the butterfly which was flying.

[00:51:57]Suddenly a red ant bit her came uh the ant bit her leaving her skin red with stinging pain. So you know that how it pains when a ant will bite you. Correct.

[00:52:10]She was having that pain. Her brother helped her by applying moist baking soda to the affected area which relieved the pain. What you think might be the reason? And so what her uh brother did was he took some amount of baking soda which was little moist. That means he mixed it with water and he rubbed it on the ant bite spot. I think what it is what is the nature of baking soda? It is basic correct. So and bitter whatever the thing went inside was a acid that is called as formic acid. So because of that the spot where the ant bit was having pain. So when he rubbed baking soda on it that was acidic he rubbed basic so it came neutralized.

[00:53:02]Because of neutralization the sting pain or whatever was there just went. So when an ant bites it injects an acid liquid that is formic acid into the skin. The effect of acid can be neutralized by rubbing moist baking soda which is base.

[00:53:21]Correct? It is simple but you may have done it but you didn't know what is the reaction of it.

[00:53:29]They have given one more situation too on the farmer's port portal that is an online platform from the department of agriculture cooperation for the farmers.

[00:53:39]Aquiry uh from a farmer states, "My plants are not growing well lately." So the farmer tells that his plants are not growing properly. After a detailed discussion, it was found that the excessive use of chemical fertilizers made the soil acidic. What is this fertilizers? They are the substances which are added to the soil to help for the plants to grow to by taking the nutrition. They are the fertilizers. So by adding more amount of fertilizers again and again and again the soil had become acidic in nature. What remedy might be provided to him. So what remedy that you may give it to him so that his plants will grow more good.

[00:54:26]When the soil is too acidic the plants do not grow well. It can be treated with lime which is basic in nature. So the soil can be treated with the line which is actually basic in nature. Then situation three, Ashwin's friend Gurbid stays near an industrial area. Okay. He stayed near the factories more. He shared with him that the fish pollution in his neighborhood lake was declining day by day.

[00:54:56]What do you think might be the cause for this? It may be due to factory waste being released into the lake. So whatever the fish fish population was there in the lake was getting decreased by day by day because that fish were dying each day. What may be the reason?

[00:55:11]You can tell that easily the waste from the factories was released into the lake. If the factory waste is acidic in nature, what could be done to save the fish in the lake? If it is acidic in nature, it can be neutralized by adding basic substance before releasing into the lake. In the factory itself, the whatever acidic waste is there for that if they are treated with a basic substance, then it will become neutralized then they can leave it to the lake so that it will be safe for the any of the animals which are living in the lake.

[00:55:47]So these are about the topics which is like acidic, basic and neutral and also about the very interesting indicators which can be used to see whether the substance is acidic, basic or neutral in nature. So we have done all these explanation and got to know about the topics along with the activities. I hope this video is helpful for you all and you liked it. So if yes, please like this video, share it and if you have not yet subscribed our channel, please subscribe it. Thank you.