Colorful Chemistry of Acids and Bases
Let me show you a magic trick. This might look like an ordinary kettle, but it's a magic kettle. And it's magic because it will pour any color that I ask it to. Oh, you don't believe me? Check this out. Pink. Hey, not bad. OK, blue. Red. OK. How about green? No, no, no. I mean, yellow. And OK. And then green. So there we go. A rainbow of colors. So I bet you're wondering how I did that. Well it's not magic. But it is some pretty cool science. My name's Tyler, and I'm
a student at MIT. And I'm going to teach you the science behind this magic trick. And I'm going to show you how you can do it yourself at home. But first we have to go to the lab and learn a little bit about some chemicals called
acids, and some chemicals called
bases. So let's go and check it out. Welcome to my lab. This is where I have all my chemicals that I use for these science experiments that I do every day. And I also brought a few of these chemicals here from home. I also
have a bunch of beakers here, and I filled the beakers with a liquid called indicator. You can see the indicator, this indicator I'm using, has sort of a blue, purplish color. And that's going to be important. Indicator tells us whether a chemical is acid, base, or neutral. Let me show you what I mean. I'm going to take a chemical here add little drops of it to the indicator. See these drops make a very light purple. And there's some pink, and some more pink, and it gets pinker
and pinker, the more I add. And now it gets darker and darker, and I eventually get a really deep, bright red. Isn't that cool? If we can add a chemical to this indicator, and it makes it redder and redder and redder-- it starts with purple and goes to pink and goes to red-- we call it an acid. So this chemical here is an acid. Let's take a look at another example. Here's a fresh beaker of indicator. And again, you can see that it sort of starts at a blue, very light purple color.
Now I'm going to take this other chemical, and I'm going to add it to the indicator. Let's see what happens now. You can see little bits of green in the indicator as I start dropping this in. Now we go to a really nice, blue color, a very bright blue. And then it becomes sort of aquamarine here, greener and greener now. And now it turns the indicator green. And I'll show you what happens if we add even more. This gets more and more yellow, until we have a yellow solution. And
it's a really bright, cool, yellow color. If we can add a chemical to an indicator and it makes it darker blue, or that brighter blue, that really nice blue, and then greener, and finally yellow-- if it can make any of those colors when we add it to the indicator-- we call it a base. So
acidsmake it pink and then red. And
basesmake it blue and then green and then yellow, if we add a whole lot of it. OK. Let's look at another example. I have a third chemical here. I'm going to add
some of it, dropping it in here, lots of drops. And I'm not really seeing any change. The color remains the same. And as you'll see, I can add as much of this is I want and the color is still going to stay this blue, purplish color. That's because this compound, this chemical, we call it neutral. It's not acid and it's not base. So it doesn't change the color of the indicator. We can add as much as we want and the indicator is just going to stay the same color. So those
are our three categories of chemicals--
bases, and then those that are neutral. You can tell whether something is acid or base or neutral by the color that it makes an indicator. You may think that this indicator is a fancy chemical that I'd only have in a lab, but actually I made this indicator in the kitchen back in my house. And you can do the same thing. We're going to need some indicator for the magic trick that we're figuring out. And I'm going to show you how to
make this kind of indicator back in your kitchen. So let's go take a look at that. OK, so here we are in my kitchen. And I want to show you how to make this acid base indicator that we've been using so you can do these color changes yourself, and so you can do the magic trick. So I will say this is pretty easy, but you're going to have to boil some water and use a stove. So make sure you have an adult around to help you with that step. Here's the stuff you're going to need.
First of all, you're going to need a red cabbage. You should be able to find something like this at any supermarket. And then you're going to need a pot to boil some water in. And then you're going to need a strainer. And that's it. It's pretty simple. So what you want to do is you want to take the pot and you want to fill it about halfway up with water. And then you want to take the cabbage, and start pulling off parts of its leaves and putting those in the pan. And you want
to fill it up until pretty much all the cabbage is covered with water. So this is a pretty good amount right about here. And then what you want to do is turn up the heat and boil water. Let it boil for four or five minutes. And then turn the heat off and let it sit for 15 minutes, 10 to 15 minutes. And after you do that, what you're going to see is the cabbage is going to lose its color. All that purple dye that was in the cabbage leaves is going to come out into the water. And you're
going to end up with purple cabbage juice. And then the final thing you need to do is you need to take this and, using a strainer, pour the juice off the top of it. And now you have your cabbage juice indicator all ready to go. Let's go and see what we can do this indicator, and then find out how we can do this magic trick. OK, so now that you've made your cabbage juice, you're all ready to start testing things around the house to see whether they're acid, neutral, or basic. and
see those cool color changes. I have here next to me a few examples of things that you can test around the house. But really anything that's a liquid or a powder, you should be able to test. Just check with your parents first to make sure that you don't use anything that's dangerous or toxic or anything. So OK everything with them first. But let's just do a quick example here. Let's say that you wanted to test a little bit of a glass cleaner here. You could spray just a
little bit into the bottom of a glass, and then add the indicator. Ooh. It turns a sort of blue green, so we know that it's a base. Or let's say that we wanted to test some hot sauce here. Add a little of the hot sauce, couple drops in there. And then all we've got to do is just add a little bit of the indicator. Oh, and we get a nice, a nice red, sort of pinkish color. So we know that this is an acid. Now let's talk about the magic trick. So how did I do it? Well, you might sort
of have been figuring parts of it out. I took my tea kettle here. And I filled it with indicator. An indicator, as you know, changes color depending on whether I add an acid or base. So what I did was I took glasses like this, and I added a little bit of acid or base into the very bottom of it. I tried to find clear liquids that were
bases. So let's do an example here. Let's say that I wanted a red color. What I do is I take a little bit of vinegar-- and I'd use vinegar
because I know that vinegar is an acid, so it's going to give me a red color-- add a little bit of this into the bottom here. Now if you're doing this magic trick, you'll be able to see the clear liquid in the bottom. But trust me, no one else will, especially if you make sure that they keep a little bit of distance, especially if you're using a clear glass, a clear glass like this, they won't be able to see it if you have it on a table. So you say that they're empty, or
don't say anything at all and people will assume that they're empty. And then go ahead and you take your tea kettle, or your pitcher of indicator, and you pour it in. And you'll get a nice red or a pink color. OK. So there are a whole wide range of colors you can get. You can get reds and you're going to get pinks and blues and purples and greens. And what I want you to do is experiment to find out which of these chemicals in your house give you these different colors. And then
put a little bit of that chemical that gives you the color in the bottom. And pour in the indicator to get that color. Now you may find that different amounts of these chemicals give you different colors. So maybe a little bit of glass cleaner will give you a bright blue, but a little bit more glass cleaner will give you a green. So experiment with all these things. There's one thing that I do want to tell you, though. You can get a really nice, yellow color by using a little bit of bleach.
But bleach can be dangerous, so make sure that you work with an adult if you're going to do this. Put a few drops of bleach in the bottom of a glass like this, add some indicator, and it turns green, and then it turns yellow. And that's how I did that thing at the very beginning when it started off green and then it turned yellow. So I hope you've enjoyed watching this video. We learned a little bit about
bases. We learned about indicators. And we learned how to do this
pretty cool magic trick that now you can use to impress your friends and family.