– My name is Lea, I am a museum educator at the National World War II Museum Today we’re gonna be doing a really fun chemistry experiment in our kitchen We’re gonna learn all about pH So before we get started with our really fun activity, first we’re gonna talk about pH, what it is, and why it’s important So, have you ever gotten a sore mouth from eating way too much sour candy, or have you gone swimming in a local swimming pool and opened your eyes under the water, and it kind of burns your eyes a little bit? So, what you’re experiencing in both of those cases is pH So, pH is essentially the measure of how acidic or basic something is So why is that important? So it turns out, pH is important in many aspects of daily life and science. (clears throat) So, when you’re baking, it’s gonna be why your cakes and your cookies rise In environmental science, it’s gonna be how we can tell whether or not soils are healthy for plants, or whether or not oceans or other natural bodies of water are healthy for the fish that live in them It’s gonna be why Drano can unclog your drain, and it’s gonna be why your stomach can digest your food So, let’s take a look here at a pH scale All right, so what we’re looking at here is our pH scale So, as you can see, at the bottom here, it’s gonna go from zero to 14 There are actually things that can fall below zero or above 14, but they’re very uncommon So we’re actually just gonna look at zero to 14 What’s really interesting about the pH scale is that neutral is actually in the middle of the scale So, seven is gonna be what we consider to be neutral It’s neither acidic nor basic As we go below seven, as our numbers get smaller, that’s actually gonna be more acidic And then, as we go higher, above seven, it’s gonna be more basic, or alkaline So something that is a zero, and something that is a 14, is actually gonna be equally as reactive and powerful, but just in different ways Whereas things in the middle are gonna be our neutral So let’s look at some examples from our everyday lives So, an example of something that’s neutral is gonna be pure water So that’s not acidic, it’s not basic, it’s just pure So that is neutral As we go towards our acidic side, some things you may already be familiar with that are acids, we have our lemons and limes, oranges, things that are citrus, have citric acid in them, so those are acidic We have vinegar, so anything that’s pickled, pickles or anything like that, are gonna be acidic We have sodas, we have sour candies Things that are strong, strong acids are things like gastric acid, so the acid in your stomach, or battery acid Looking on the other end of the scale, things that are some weak bases, we have baking soda, toothpaste, things like that A lot of our soaps and detergents are also bases, whereas Drano and bleach are gonna be some really, really strong bases So, what exactly is pH? So, pH we can think of as standing for the power of hydrogen So hydrogen is gonna have everything to do with what pH means So pH is essentially sort of a shorthand for the concentration, or the amount of hydrogen ions in a solution So what is an ion? So an ion is a positive or negatively-charged molecule or atom So how might those be formed? So let’s take a look at an example In our webinar on the Manhattan Project, we learned a little bit about water and the subatomic particles that make up water We learned that water is made up of (clears throat) two hydrogen atoms and one oxygen atom And these atoms are bonded together through their electrons So our electrons are negatively-charged particles, and the hydrogen and the oxygen share those electrons and are bonded together So, when they form the molecule water, then all of the electrons, those negatively-charged particles, are gonna kind of gather together on the oxygen side, and make the oxygen side of the water a little bit, slightly negatively-charged So then that’s gonna leave our hydrogen, that has now the proton in the middle, in its nucleus, that positively-charged particle, is gonna make the hydrogen sides more positively-charged So, if it comes into contact, if it meets another water molecule,

then the positively-charged hydrogen, on the first water molecule, is gonna be weakly attracted to the negative side, the negative oxygen on the new water molecule So they’re gonna bond together, that positive and the negative are gonna be attracted to each other, and they’re gonna form a weak bond Now, sometimes that bond can be so strong that the new water molecule is actually gonna pull over that hydrogen over to itself So, what’s interesting here is that you’ll notice, that original water molecule now has kind of broken into two pieces And what’s left is what’s called a hydroxide So that is gonna be a negative ion So it’s negative, because you can see, when the hydrogen hops over to the new water molecule, it actually leaves behind its electron So this red electron right here, it’s being left behind So because the electrons are negatively charged, since we added, or we left behind that negatively-charged particle, that makes the hydroxide a negative ion, okay? So then, we can look at our new water molecule, that received that hydrogen ion, which actually now is only just the proton, because it left behind its electron, so it’s just our proton Our protons are gonna be positively charged, and so now, this new water molecule, with its new hydrogen, positive hydrogen ion, is now gonna be known as hydronium And that’s gonna be a positive ion, okay? So, for simplicity, we’re going to just get rid of that extra water molecule, we’re just gonna look at the two pieces that we have here So we have a hydroxide, which is negative, with that extra electron, and then we have our hydrogen ion, which is the hydrogen without its electron, just its proton A hydrogen ion, okay? So, pH is measuring the concentration, or amount of that positive hydrogen ion, so that one you see on the right So it’s measuring the hydrogen ions in a solution So what is our unit of measure when we’re talking about these hydrogen ions? So, hydrogen ions are measured in a concentration, a unit of measure called moles per liter So liters are about a quarter of a gallon, but what is a mole? So a mole is a unit of measurement which is equal to about 600 sextillion molecules or ions So this sounds like a lot, but molecules or ions are very, very tiny, so a mole is still very, very small It turns out that water has about 0.0000001 moles per liter This is a very, very tiny amount So since this number is a bit ridiculous, a mole is a bit ridiculous, we’re gonna just write it in a shorthand So 0.0000001 moles per liter can actually be written in a shorthand, that looks like one times 10 to the negative seven So we get this negative seven, because we have seven numbers, or seven decimal places to the right of the decimal point So, we, 0.0000001 is equal to one times 10 to the negative seventh power So pH is gonna simplify that even more, and it’s just gonna take this little number up here, just gonna take this little baby number seven, it’s gonna make it positive, and just take that So pH seven is basically just representative of the amount of hydrogen ions It’s just saying that per liter, water has 0.0000001 moles per liter in it But we don’t wanna say that every time, so we just simplify it, and we say it has a pH of seven, okay? So let’s take a look at another example If we go all the way down the acidic side of the scale, to gastric acid, that’s our stomach acid, that has actually much more, about a million times more hydrogen ions in it per liter So that is a little bit of an easier number to look at, 0.1, it’s closer to one One moles per liter So that can be written as one times 10 to the negative first power Again, we’re gonna simplify that by taking this small number up here, we’re gonna make it positive, and we’re gonna have pH of one So now we’re gonna go to the entirely other side, we’re gonna go look at Drano This has a very tiny amount, a very tiny amount of hydrogen ions in it It has zero point 13 zeros and a one moles per liter So again, I don’t wanna write that every single time, so we can write it in a shorthand of one times 10 to the negative 14th, because we have 13 zeros and then a one, so that’s 14 Again, it’s a smaller number, the numbers are below one, so it’s a negative,

so the pH is gonna take that tiny number, that 14, the negative 14, we’re gonna make it positive, and that’s gonna be our pH So it’s really just a shorthand for these kind of ridiculously tiny numbers, just to make it easier It’s representative of something So, okay, so now we understand what the numbers kind of mean, but why is seven, why is neutral in the middle? It’s not the solution with the most hydrogen ions, and it’s not the solution with the least hydrogen ions, so why is it neutral? Okay, so to answer that question, we’re gonna circle back to how our hydrogen ions are formed So we remember that we had our hydrogen ion, which was positive, but we also had our buddy, the negative ion, the hydroxide So whether or not something is acidic or neutral or basic is gonna depend on whether or not the amounts of these two ions are equal Okay, so in water, water has 0.000001 moles per liter hydrogen ions, and it also has 0.000001 moles per liter of hydroxide So they’re actually equal, okay? So since they’re equal, our positives and our negatives are equal, they balance out, and that makes it neutral So neutral is in the middle Now if we go towards the acidic side, we get more hydrogen ions and fewer hydroxide ions So now the balance is off, and because of that, it becomes acidic, or more reactive, okay? So then if we go the other side, now we have fewer hydrogen ions, and more hydroxide ions, and again, the balance is off, but in the other way, and that also makes it more reactive So now we have a base, okay? So to sum up, pH, the numbers are, essentially are a shorthand for the concentration of these hydrogen ions, and whether or not it’s an acid or a base is gonna depend on if those hydrogen and those hydroxide ions are equal Acids are gonna have more hydrogen ions, and bases are gonna have less, okay? So, one of my favorite things about pH is these things called pH indicators So pH indicators are really cool chemicals that change color, depending on if they come into contact with an acid or a base So one that you may experience in school is called litmus paper, so it’s a special kind of paper that’s gonna change color, whether or not it’s in an acid or a base But there are also natural pH indicators So, some examples are beets, red onions, blueberries, excuse me, curry powder, and red cabbage So my favorite one, and the one we’re gonna be doing today, is red cabbage, because red cabbage, it changes a wide range of colors Some of these pH indicators only change one or two colors, red cabbage is gonna change a wide range of colors, okay? So you can see in the center here, red cabbage juice, in a neutral environment, is gonna be sort of this purpley-blue color, at that seven As we add an acid to it, it’s gonna turn purple and red and pink, and if we add some bases to it, then it’ll turn blue and green So it’s really pretty So if you wanna make your own pH indicator, using a red cabbage, it’s super simple You just need a red cabbage, a pot to boil some water, and a strainer So today, what we’re gonna be doing, is we’re gonna be testing these five household ingredients that I found around my house So we have some tap water that we’re gonna be testing, a lemon, some bleach, some sparkling water, and some baking soda First, what we’re gonna do, is we’re going to watch a video about how to make your own cabbage juice All right, so the first thing you’re gonna do is you’re just gonna chop up your cabbage loosely And you’re gonna stick it in a pot of water, make sure it’s full Stick it on the stove, and bring it to a boil Once your cabbage is boiling, you’re gonna turn off the water, and let it kind of marinate and sit there for a while, until it cools off Once it’s cooler, you’ll bring it over to your sink, and you’re gonna strain out those cabbage leaves So you’re gonna pour the water into another bowl, and strain out the leaves, so you’re left with just the liquid there So you can see, we’ve kind of taken out some of the color, that red color, and we’re left with the juice

Okay, cool So, (clears throat) okay, we can now start our experiment, now that we’ve prepared our juice So you can see, I have my five cups here, lined up They have our cabbage juice in it I’ve also printed out my pH scale, so when we pour some stuff in there, we can check out what relative pH It’s not gonna be precise, but it’s gonna give us a ballpark idea of the pH of our substances Okay, so, scoot back a little, okay So let’s start with our lemon Okay, so based off of what you guys know about lemons, before I pour this in, I want you guys to make a hypothesis, or a prediction, of what color you think this is gonna change So looking at our scale, do we think lemons are gonna be more pink, are they super acidic? Or are they basic, are they gonna turn more blue and green? Okay, so let’s find out I’m gonna pour it in All right, hopefully y’all can see this So it actually turned a very bright pink So if we’re looking on here, and we wanna match it, it’s gonna fall actually pretty perfectly under the pH of two or three, down here, which actually does match what we know about lemon juice Lemon juice is a strong acid, it’s very acidic, and so it turns our lovely cabbage juice a nice pink color All right, so the next thing I’m gonna look at is I’m gonna look at my sparkling water What do y’all think? It’s water, but it has carbonation in it, and it also has some flavors, I think the one I have, (clears throat) it’s actually lime-flavored (clears throat) Excuse me So, we’re gonna try this out, to see what color it changes All right, okay, so that has turned sort of a light purple color All right, so looking at my scale here, it actually looks like it’s about at a five or a six on our scale So it’s still acidic, it’s below seven, right? So it’s below seven, so it’s still acidic, but it’s not as acidic as our lemon juice, it’s kind of, it’s a mild acid there Okay, so let’s check out our tap water Tap water, again, is not pure water. (laughs) So we’re gonna see if we think it’s basic or acidic Or if it isn’t So here’s our water glass Pour that in All right, so it did change a little bit of a color It’s not as purple as when it originally started, we can kinda compare So it actually fell, it’s a little bit bluer, so it did fall in the eight or nine category, which checks out Tap water is usually made to be a bit more basic, especially here in New Orleans, which is where we are They do make the water more basic, so that it doesn’t leach out as many metals from the pipes that the water is running through All right, cool Alrighty, so the fourth one we’re gonna look at, we’re gonna look at baking soda, so I actually mixed some baking soda in with some water, just to make it easier So let’s see what color that changes All right, so that has changed a really pretty green So let’s take a look at our scale here So, that has fallen a little bit more down the base side, as well It’s not super precise, so I can’t really tell, maybe between a nine and a 10 or so But we do know it’s a base It kinda came out as a base All right, so the last thing I’m gonna do is I’m gonna use some bleach So I have a little, tiny bit of bleach, mixed with some water in here, so we’ll see color it changes (cutting board bangs) Whoop All right, so that has changed our water to be a very light yellow So that checks out, because we know bleach to be a really, really strong base, right? So we’re over here, almost off this scale, because this is a bit green, and that’s even lighter than that So we can see from this that bleach is a really, really strong, strong base All right, so now that we’ve gotten to try some things out at home, I want you guys to try out, make your own pH indicator, test out some things around you, see what they are Do they match your predictions? Is something acidic that surprises you? Is something a base, that you didn’t know was a base? So yeah, try it out at home We’re gonna end here with looking at how this is relevant to World War II

So, in World War II, as we all know, a lot of things were rationed during World War II So families and people were really, really encouraged to grow and preserve their own food As you can see, a lot of these propaganda posters were around, encouraging people to grow their own food and to can things So pH is really, really important in canning So there are two methods of canning There’s water-bath canning, and then there’s pressure canning And whichever method you’re gonna use is gonna be dependent on the pH of whatever it is that you’re trying to preserve or can So water-bath canning is much simpler, you basically just submerge your cans in boiling water, it’s much simpler, it’s much less expensive, less complicated When you go to pressure canning, you’re gonna need a specific device for pressure canning So it’s much more expensive During the war, so these were made of aluminum back then, and aluminum was rationed at that time, so actually, these pressure canners were rationed, and people were encouraged to share pressure canners within their families and neighborhoods, and they were also a little bit more dangerous They were known to explode, because they have to bring up the pressure inside to such a high pressure that it could explode if it malfunctioned So, the way these things work, water-bath canning is just using, it’s bringing it up to the temperature of boiling water And it’s using boiling water, and then the acid, because the acid in the fruit or the vegetables that you’re canning, to kill the bacteria For pressure canning, you need to use pressure canning for anything that has a pH of 4.6 or above So anything that isn’t very strongly acidic, you have to use pressure canning Anything that is more acidic, the acid itself, along with the heat, is able to kill the harmful bacteria, but anything above that, the heat alone, and the acid alone, is not enough to kill it So you need to bring it, the pressure canning is gonna bring it to a much higher temperature, in order to kill that harmful bacteria Okay, so there are a couple of ways you can actually bring down the pH of a food, to make it easier to preserve One of those ways is pickling So we have put together a recipe for you guys, if you wanna try pickling at home, you don’t need to can these, these are good in the fridge for up to a month Alrighty, so let’s take a look at some questions Okay, alrighty So, one of our questions is, why red cabbage? Can I use normal cabbage, can I use green cabbage? No, you cannot use green cabbage, you have to use red cabbage The red cabbage has a chemical in it called an anthocyanin, and that particular chemical, it’s also found in blueberries and red and purple grapes, it’s that particular chemical that you’re leaching out, and that’s what you’re using as the pH indicator Okay, so, somebody asked, don’t neutrons have a neutral charge, and negative charge are electrons? Yes, that is true So neutrons are the neutral charge, and the negative charge are electrons, so within an atom, the number of protons, so neutrons are neutral, right? So the overall charge of an atom, or an ion, is gonna be basically the balance between the protons and the electrons So, when we’re looking at our hydronium, when we’re looking at our hydroxide, the negative ion, if you counted up all the protons and the electrons, because it kept that electron from the hydrogen that left, it now has one more electron So all the other electrons and protons cancel each other out, but it has an extra electron, which makes that negative And then, in the hydrogen, the hydrogen actually doesn’t have a neutron, it just has a proton, and it lost its electron So since it doesn’t have an electron to balance out the proton, then it’s a positive charge So hopefully that helps Okay, yes, okay, so Ava wants to know if you can use red onion And yes, you can So that doesn’t have as wide of a range If you check out our PDF on using cabbage juice as a pH indicator, we have a really cool graphic in there, actually, that shows some of these other natural indicators, and the range of colors Red onion is on there, and it does change, I think a couple different colors, but not as wide of a range But yeah, definitely, please still try it out, and send us photos, I would love to see how it works

Okay, so one other question, what made aluminum the ideal metal for cans at that time? Okay, so aluminum is a type of metal that is actually very resistant to corrosion It’s a metal that’s not gonna rust It can easily support different pressure from carbonation that was required to package things like soda And it was strong enough to withstand pressure From pressure canning and stuff like that All right, so I think that’s all the questions we have for today Thank you guys so much If you guys end up making any pickles, or testing out anything, please send us videos on Flipgrid, or send us some photos, we would love to see your guys’ experiments in your kitchen All right, thank you so much for joining today, guys See you later