Chemistry Colleagues on Science Trek

JOAN CARTAN-HANSEN, HOST: Chemistry is everywhere and you can do some chemistry experiments just with the things around your house.

(MUSIC)

CARTAN-HANSEN: Chris Saunders and Christina Mottishaw are chemists. They’re in my kitchen to show you how to do an at-home chemistry experiment. (sound effect)

CHRIS SAUNDERS, CHEMIST: So, scientists use different ways to determine whether something is an acid or a base. And one of those ways is through the use of what are called color pH indicators. And so, these are compounds that change different colors, whether they’re in a solution that’s more of an acid or a base. So, one of those, uh, plants that has this kind of indicator in there is red cabbage. So, what you’ll need for this experiment is some chopped up red cabbage.

CARTAN-HANSEN: You take the red cabbage leaves and put it in a Ziploc bag with some water and squish it until the water turns color.

SAUNDERS: So, right now you’ll notice that the color is kind of, of this blue color, not quite purple like the leaves because the water that we put this into is relatively neutral. It’s not quite acidic, not quite basic.

CARTAN-HANSEN: Put the water, not the cabbage leaves, into clear containers.

SAUNDERS: Okay, so here is our starting point and we’re gonna now test some of the compounds that we’ve got from home to see if they’re acids or bases. So, for the liquid ones, a good idea is to use a straw or if you have a small eyedropper, um, or maybe if you have a science kit at home, you might find a pipette that you might use. But anything that can safely transfer that liquid would work. So, I have some vinegar. So, vinegar is another name for acidic acid. So, as I put the straw on there, what I’m gonna do is that straw, some of the liquid’s gone up into the straw. And if I just take the straw out, it just falls out. So, I’m gonna put my fingertip on the front and as long as my fingertip is on the top of that straw, the liquid won’t come out. So, I’m gonna take a little bit of that acid and I’m gonna drop that into my container. So, as you notice, there is a distinct color change. So as that turns red, that tells us that that vinegar, that acidic acid is an acidic compound. And so other compounds that are also acids would give you a similar color change.

CARTAN-HANSEN: Christina is going to show us how to test solids She puts some baking soda in a cup and adds water. And then, she gives it a good stir. SAUNDERS: Okay, so just like before, I’m gonna use a straw and let’s see if something else happens this time. If baking soda is different than the vinegar, all right, I might need more. We’re just gonna pour that in there. So, in this case we didn’t see much of a color change and so a variety of things might be happening. It might be that the water was already kind of basic. So, we would expect that that baking, baking soda is basic. And so, we might use this as a comparison to say, well anything else that kind of has this blue color, you’ll notice that it is a little bit different than the original purple. That anything that turns that blue is a similar type of compound in this case a base. So, let’s test some other things. So, let’s test some soap. You can use any kind of soap, but as long as it doesn’t have a really bright color to it, because sometimes um, some of those soaps will have a dye in there and that dye will interfere with what that color looks like. So, I’m gonna put a little bit of this clear soap right into my container.

CHRISTINA MOTTISHAW, CHEMIST: What is your guess, Chris? Is it acid or base?

SAUNDERS: Well, it depends on the soap, but most soaps are little bit basic. And so, you’ll see that the color change is about the same as our baking soda. So, baking soda is a base and a lot of soaps are also basic as well. Notice that they’re different than that acid that we put in there. So, let’s see. So, Christina, what would you think might be another acid? Might be something that looks like the vinegar.

MOTTISHAW: I really think lemon juice. It’s so sour when I eat it. I think it’s a little acidic.

SAUNDERS: So, Let’s test some lemon juice. So put a couple drops in there and watch what happens. I’m gonna stir this a little bit, but already we can start to see that color change. So, we can move this over here. You can see that it’s turning that same color so we can compare those two compounds even though they’re different, they’re both considered acids. And let’s do one more. So, I always think this is a cool one because oftentimes some of the stuff that we like to drink is fizzy. So, what makes this stuff fizzy is dissolved carbon dioxide gas. And we oftentimes don’t think of a dissolved gas as being an acid or a base, but actually carbon dioxide when you dissolve it in water. I’m gonna open this up, hopefully it doesn’t make a mess. You can hear that gas coming out as I open it. So, in those bubbles fizzing up, that’s that carbon dioxide. Carbon dioxide can make small amounts of carbonic acid in that solution. So, if there’s carbonic acid in here, we should see it in any sort of fizzy drink when we put this in our indicator. So, I’m gonna get a clean straw and give it a test. And it doesn’t have to be a sugary drink, it could just be sparkling mineral water or anything that’s carbonated. You would expect the same result. So, you’ll see that it turns that pink color. And that’s to show that this is slightly acidic. So even if you don’t think of something as a acid or a base, you might be surprised by what you find out. So, we would encourage you then to think about other types of compounds that you might, other materials that you might find in your house, other types of foods or drinks or anything that you are interested in. You now have a way to make a really easy, really quick acid base indicator and you can do your own experiments, make your own guesses, and then confirm whether those things are acids or bases with your red cabbage indicator.

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