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The Air We Breathe…It’s a Gas!

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We live at the bottom of an ocean of air. Most adults take around 29,000 breaths a day, children breathe a little faster; but what is in this air we breathe? What are the gases in the air? How much of each gas is there? Do these gases have different weights? How cold are liquid nitrogen and dry ice, and where did those names come from? Come join us to explore these questions at this family friendly presentation with hands-on experiments.

Speakers: Janet Hannon and Stan Mroczkowski


Public Domain.


The Air We Breathe…It’s a Gas!

William Werkheiser: Good evening. Welcome to our Public Lecture Series this warm evening. My name is Bill Werkheiser. I'm the Associate Director for Water here at the USGS.
Just a little bit about our Lecture Series, these lectures are designed to allow us to showcase some of our best and brightest in the community that interact with you folks. Tonight is a little bit different than the other lectures in one way. It's a lot better in other ways.

Tonight it's our pleasure to have Janet Hannon and Stan Mroczkowski here to talk to you, with you the community. Janet and Stan are chemists in our Stable Isotope Lab. Now who knows what stable isotopes are?


William Werkheiser: I'll let these guys tell you what they are working on. But Janet and Stan have come here before and they were honored to be part of the American Association of Advancement in Science and in the Science Camp here at Reston that we have.


Usually we have a lecture with PowerPoint here and people nod off. So sit back and enjoy. Without further ado, Janet and Stan.


Janet Hannon: Thank you, 

We started doing this back in, well, I started doing it in the 1990s because they asked for exhibits for the Open House. And I thought, 'Stable Isotopes. Open House. No, it does not mix.' So what do I do that would be fun and interesting for people? We work in our lab with liquid nitrogen and dry ice, which are two of the coolest substances that I've had the pleasure of working with, so I came up with an idea of how we work with them.

And then it kind of got a tour and got a little bit changed. And then in 2000, Stan came to work 
with us, and it was like, boom. He had all kinds of great ideas.
So we've been refining this over the last 10 to 15 years, but it's been a long time. And we have to change it then, too, depending on the size of the room and the audience that we have. But people have always enjoyed it before.

Maybe you guys know: what's something that you use everyday from the moment you're born until the moment you die? Yes.

Audience 1: Air!

Janet Hannon: Air, exactly.

Janet Hannon: OK.

Stan Mroczkowski: All right. Good answer!

Janet Hannon: So that's what we've got. We've worked with some of the gases in the air. What's air made of? What's air made of?


Audience 3: Nitrogen.

Janet Hannon: Nitrogen. What else? oxygen. What else? Any other? Yes.

Audience 4: Carbon dioxide.

Janet Hannon: Carbon dioxide.
Audience 5: Argon!

Janet Hannon: Argon.
Stan Mroczkowski: There we go.

Janet Hannon: That's a good one. Who else? What's in balloons?

Audience 6: Helium.

Janet Hannon: Helium. Yes. What was in the Hindenburg?
Audience 7: Hydrogen.

Janet Hannon: Hydrogen. There's hydrogen in the air. Any other guesses?
Audience 8: Sulphur.

Janet Hannon: Actually, yes, there is sulphur in the air. We don't have that on our charts but yeah, because there's so many.
So this is the proportion of gases. There's this much nitrogen. Seventy-eight percent of all the air is nitrogen, 21% is oxygen, about a little less than 1% is argon, and everything else that you said fits on this little off, right there. And here you go.


Carbon dioxide is the biggest gas. This is PPM, parts per million.
If you had pizza and cut it into a million slices, 330 of them would be carbon dioxide, 18 would be Neon, five would be Helium, two would be methane and one would be krypton, 0.5, hydrogen and 0.5 nitrous oxide, and this is laughing gas. And xenon, which is our favorite, this is the tiniest. That's not parts per million; that's parts per billion. Really small.

Stan has his PowerPoint presentation. I never used this before, so I have to look and see what to do next. Brad Sears measured the auditorium for us. Those of you who work with us know Brad. He measured all of the honeycombs in the sides, everything, and it's 56,000 cubic feet of air in here.
Now if we can take this air and divide it up into gases to segregate them...


Stan Mroczkowski: Purify the gases.

Janet Hannon: Purify the gases.

Stan Mroczkowski: Let's put all the nitrogen in one spot, all the oxygen in another spot; what would that look like?

Janet Hannon: See this piece of blue tape here? Most of you can see, this piece of blue tape right here, if you could divide all across here, all the way up, all the way across, and all the way back to the stage, that's all oxygen. If you take a piece of green tape and move all the way back, the whole rest of the room is nitrogen. And you see the little yellow crosshatches here? That's argon. Right here, this, all the way up to the ceiling.

Stan Mroczkowski: About a one-foot slice of the room right here would be argon.

Janet Hannon: But then there are other gases, too, that you've all named.


Stan Mroczkowski: I think someone mentioned carbon dioxide? There we go. We've purified all the carbon dioxide in this room, fit about this big. This is about 18 cubic feet.

Janet Hannon: And we measured all this.

Stan Mroczkowski: Yeah. We actually did. We did.

Janet Hannon: With an Excel spreadsheet.

Stan Mroczkowski: Yeah.
Somebody mentioned Neon. There's about one cubic foot of neon in this auditorium. It's a small amount. What have we got here? Helium. Not much there. We're getting smaller. Methane. I heard methane, someone mentioned that. Another greenhouse gas there. About that much.

Let's see, krypton. Someone mentioned krypton. Getting smaller. What do we have here? Oh, it's red. I think that's a hint. That's hydrogen, right? This red is the hydrogen slot hole.


And then coming down, we have nitrous oxide, just a little bit, about this much. And then the last one, you might find this gas in your headlights if you have fancy cars. Xenon. Just a few tiny bits; it's at 87 parts per billion. This is 87 parts per billion of this room.
So there we go.

Janet Hannon: So we talk about these different gases. They have different properties. They're not all the same. oxygen, we all need to live. So they all do different things to us and they are different from each other.

And one of the things that we don't think about is that we live at the bottom of this ocean of air. There is so much air above us. And it exerts a force of 14.7 pounds of air per square inch. So each inch of us has 14.7 pounds of air coming down on us.

How do we know the gases have weights? When I first thought about it, I wasn't sure that it would work or not, but we bought balloons.

Stan Mroczkowski: These balloons here, these color balloons, have pure gases in them.

Janet Hannon: We have gases upstairs...

Stan Mroczkowski: Two of the gases on here are actually lighter than air. Can you guess which ones?

Janet Hannon: Which ones? 

Stan Mroczkowski: The ones over here.

Janet Hannon: What gases are lighter than air?

Audience 9: Helium.

Janet Hannon: Helium. What's the other one?

Audience 10: Hydrogen.

Janet Hannon: Hydrogen, yes.

Stan Mroczkowski: Hydrogen, right.
Janet Hannon: So which one do you think weighs more than the other? Which one is heavier? Because they're not exactly the same.

Audience 9: Helium!

Janet Hannon: Helium is lighter? Or heavier? What do you think? Just guess. That's what science is. Science is guessing and then trying to figure out.

Stan Mroczkowski: So to find out, we'll use this very, very high-tech piece of equipment here.


Stan Mroczkowski: We pride ourselves on the way we shine a light on this.


Stan Mroczkowski: OK. So we have hydrogen in the red balloon, because hydrogen is flammable, and Helium is in this one.

Janet Hannon: It's a silver balloon because it's a noble gas.

Stan Mroczkowski: So let's see what happens. Oh! So hydrogen is lighter than helium. 
But when you talk about weight, you talk about the molecular weight of a gas; hydrogen is 2 and helium is 4. So hydrogen is half the weight of helium. So that's two gases that are lighter than air.
We'll use this to make sure they don't fly into the rafters.

Janet Hannon: Because we'll never get them back.


Stan Mroczkowski: So how about two gases that make up the majority of air? If you remember back to the pie chart, we had a big green slice; Eighty percent of the air, nitrogen. And then we had a blue slice; about 21% of the air is oxygen. So which one do you think is heavier? Who votes nitrogen?

Janet Hannon: Vote for nitrogen?

Stan Mroczkowski: All right, just a few. Who votes for oxygen?

Janet Hannon: All right. We have a variation.

Stan Mroczkowski: Oh, yes. oxygen is indeed heavier than nitrogen. Nitrogen's molecular weight is 28 and oxygen is 32. I'll leave this one on.
So we have a new contender in the ring.

Janet Hannon: Argon.

Stan Mroczkowski: This one, if you remember the pie chart, the yellow slice, about 1% of the air is argon. OK, new challenger. Who votes oxygen? Who votes argon? I'm so sorry. All right.


Janet Hannon: Yes.

Stan Mroczkowski: Yes.

Janet Hannon: And it's gold because it's a noble gas.

Stan Mroczkowski: Yeah, so the molecular weight of Argon is 40.
I don't know if you noticed, but argon really pulled down that side of the balance. That's because the difference in weight between these two balloons, because the difference in molecular density is 8 as opposed to 4 with the nitrogen-oxygen, the difference of weight here is twice the difference between nitrogen and oxygen. So it pulled it down a lot faster.

All right, Argon is the champ. So we leave it there and move on. This balloon is filled with carbon dioxide. Pure CO2. All right. Let's see. Oh, and incidentally, I should say, actually all these balloons weigh exactly, and I mean exactly, the same amount, down to the milligram.


And as you can see here, I have some tape on some on these. So I've weighed all the balloons and figured out which one is the heaviest, then I kind of trimmed up the weight of all the other balloons so that they are all exactly the same. So we really are measuring the difference in weights between the gases inside these balloons.

All right, here we go. Argon against CO2.

Janet Hannon: Guesses?

Stan Mroczkowski: Guesses? Who votes CO2? All right. Who votes argon? Oh some slip inside...

Janet Hannon: All right. Let's see.

Stan: Yeah, CO2. So CO2, molecular weight of 44.

So, this is an interesting gas. I have a smiley face on here because this is nitrous oxygen, otherwise known as laughing gas. If you go to the dentist, you may get this.


Audience 11: Why is there a smiley face?

Stan Mroczkowski: What's that? 

Janet Hannon: It's the laughing gas.

Stan Mroczkowski: The smiley face is the laughing gas.

Audience 11: Oh?

Janet Hannon: Nitrous Oxide.

Stan Mroczkowski: Nitrous Oxide.
So here we go. Let's see what happens. I don't know, this is a little bit inconclusive. Let's weigh some balloons and see what happens. This one, this side, maybe I'll do it again.
Janet Hannon: We've never exploded a balloon. Actually, we use these balloons year after year.

Stan Mroczkowski: All right, let's see what happens now. It's coming down.

Janet Hannon: It's ventilation.

Stan Mroczkowski: I think there's a draft.
So this one looks heavier on that side? No. That one is heavier on that side? Do we have the same amount. And actually, the molecular weights are the same. So really, these two are exactly the same. And I actually weighed both of them before we came down, and they are really...


OK. Now let's try another one.

Janet Hannon: Nitrogen, air?

Stan Mroczkowski: Yeah.
The next one we'll try is nitrogen against air. Now air, of course, is a mixture. I didn't put the molecular weight. I probably should have calculated the average, and you can get the average molecular weight for air. What do we know? We know that's mostly nitrogen, and it has a bunch of other gases that are heavier than nitrogen.
So what do you think will happen? Yeah, it's a little bit of mixture of air and those gases. OK. There we go. Have it settled away.


How many molecules of gas do you think are in either one of these star balloons here? Well, when we're trying to describe the number of atoms and molecules, we use a quantity called the mole. It's on the side you guys, like this is something that you learn in high school that's complicated and some people don't get it after they've learned it.

A mole is number. And it actually is a really, really big number. And we need to use a big number because atoms and molecules are so tiny and there's a lot of them. So a mole is a quantity. We have other words in English that denote quantity, right? Like a dozen? 144. When we can talk about paper, 500.

So the mole can be written this way. Now, for those of you who haven't had scientific notation, this is 6.022 times 10 to the 23rd power. And all of this is, it's a fancy way to manage the zeroes in a number. We have a really, really big number. So it's basically 6022 followed by another 20 zeroes. That's how big a mole is.
There we go. Sorry, let's get a little technical here. This is as technical as this talk's going to get. The mole is defined as the amount of substance that contains as many elementary entities, the things that we have in molecules, as there are atoms in 12 grams of the isotope carbon 12. It also anchors our periodic table.


So by this definition, a mole of any pure substance has a mass in grams exactly equal to that substance's atomic weight. What I mean by that, practically speaking, is if we go to the periodic table. Well you guys have seen that. We have these little boxes through each element, and we'll see numbers like this.
The top number here is the atomic number. That's the number of protons that this one has. But then down here we have the atomic weight. So finally one mole of argon would weigh 39.95 grams.

So let's try to wrap our head around this. Now, this number is just giant. It's huge. It's unbelievably huge. We have a mole of argon and we have a mole of nitrogen and we have a mole of oxygen. So I propose we think of something else.


Let's say we have a mole of apples. We're going to have this many apples. So the question is, how many times do you think you could fill the world's ocean basins with apples? 

If you took all the water out of the Atlantic Ocean, all the water of the Pacific Ocean, the Indian Ocean, the Arctic Ocean, the Southern Ocean, take every drop out, start with that line of apples, you fill it up, how many times do you think you're going to have to do that in order to exhaust your pile of apples?
Yeah? OK, so down here in the X-ray, I have some scratch notation. So five. You guys be 1, 2, 3, 4, and then to 5? You think five? No. Ten? Ten times? Ten? No.

What about 85? No. Keep going. You would have to fill and empty the world's ocean basins 165 times in order to exhaust your one mole of apples.

All right, let's try one more. Let's pretend again, a mole of apples, this many apples. We're going to line these up one right next to each other. And by the way, this apple's about eight centimeters across. That makes the calculation. So you have an Apple Macintosh. So we're just going to line them up one next to the other, next to the other, next to the other. We're just going to keep going out into space, just as far as we need to go.

And then I'm going to be here with my laser pointer, which is light. I'm going to turn on the light, and it's going to start racing along that line of apples. So how long would it take the light to reach that mole of apples? 


Now keep in mind, the speed of light is 300,000 kilometers per second. A little over three seconds, about a million kilometers. Seconds. So how long do you think it would take?
Audience 13: Six years.

Stan Mroczkowski: Six years?

Janet Hannon: Six years?

Stan Mroczkowski: Any other? All right.

Audience 9: Ten years?

Janet Hannon: Ten years? OK.

Stan Mroczkowski: It would take five million years for light to travel that distance. The mole is a huge, huge number. So light traveling for five million years, that's a distance we would call five million light years. That's actually equivalent to a distance.

Does anybody recognize this guy here? Happens to be our closest fire galaxy neighbor called Andromeda. Conveniently, Andromeda is two-and-a-half million light years from Earth. So our mole of apples would actually travel from Earth to Andromeda and back again.


Audience 9: I don't see.

Stan Mroczkowski: It's OK.
Since we're speaking of galaxies and stars, I thought this was pretty interesting. I don't know if anybody caught this in December. This is actually the technical publication put out by these two gentlemen; Van Dokkum is at Yale, Conroy is at Harvard. They're astronomers, and they tried to get a clear estimate of the number of stars in the universe, and their conclusion was that an estimated number of stars is 300 sextillion. Sextillion, a big number. So you have million, billion, trillion, keep going.
Perfect. Thank you for the segue.


Three-hundred sextillion, that's a three followed by 23 zeroes. Or if you write it in scientific notation, three times 10 to the 23rd. Or if we just heard that, well, a mole is about six times 10 to the 23rd. As a chemist, I would rather say the universe has half a mole of stars rather than say 300 sextillion. And I've got to admit, as a chemist I'm fond of using it and comforting.

Audience 15: So what you are teaching us this week is that less is mole?


Stan Mroczkowski: All right. So don't get too excited so what's going on. We're talking about here.

The number given in chemistry is that one mole of gas at 25 degrees Celsius and 1 atmospheric pressure will be called, SLC stands for Standard Laboratory Conditions. That's what we're experiencing right here. It's roughly 25 degrees Celsius and we're all in 1 atmospheric pressure.


And one mole of gas, it doesn't matter what gas, argon, helium, hydrogen, oxygen, will all occupy about 24 1/2 liters, 24.47 liters of space. The volume of this balloon is 15 liters, and I know that because I've fill them up with water and I then I weighed it based on 1 liter of water into kilograms...
So 15 liters divided by 22.47 for one mole is about 0.6 moles of gas inside of this balloon. Or analyze the numbers, 360 sextillion molecules of Argon in this one balloon. So there's actually more molecules of gas in each of these balloons than there are stars in the universe, which is pretty...

All right, one more fun fact. Just one more of these, then we'll move on. If one mole occupies 24 1/2 liters, half a mole will occupy 12 and 1/4 liters. The average adult breath volume, the breaths you're all taking here just sitting quietly, are roughly about half a liter. Just slow, gentle breaths.

And if we take another breathing rate for adults of about 12 per minute, everyone who's sitting here you're not moving, you're not working out or running here or anything, what that means is an adult will respire a number of molecules of air equal to the number of stars in the universe approximately every two minutes. So we've been sitting here for about 20 minutes and have breathed many, many universes of air molecules.


OK, let's move on. So we've been talking about gases, but if we take a gas and we cool it down, what can happen? Well, it can change phase, right?

If we keep careening down, it can turn into a solid. And we can take any one of these gases that we have and bought it for manufacture. Took carbon dioxide, cooled it way down, turned it into a solid. This is called dry ice. How cold is dry ice? The top of that thermometer there represents room temperature, so that's 25 degrees Celsius.
We all know water, water at ice, freezes at zero. How cold do you think this is? It's 108 below zero Fahrenheit or 78 degrees below zero Celsius. It's really cold. I think that I saw once that got as cold as this on Antarctica once.

Janet Hannon: Yeah.
Stan Mroczkowski: OK. Dry ice. It's an interesting name. You know what, how can ice be dry? What do they do, take a paper towel and dry it up? What's going on?

Normally, we have three states of matter. I'm sure a lot of you guys learned this: solid, liquid or gas, most compounds will have these three what we call 'atmospheric pressure'.
From a gas, if you cool that down, you can condense it to a liquid. Liquids can be frozen into solids, solids can melt to liquids, and liquids can evaporate to gas. And you can get that quite easily with water.


Carbon dioxide plays by completely different rules. The reason why it's called dry ice is that there's no liquid phase at atmospheric pressure. It goes from solid straight on to a gas. And that process we call 'sublimation'. And you can also freeze it down to a solid later.

So it's kind of fun here to see that it's... a piece of Plexiglas here, and it just glides very easily here when I touch it, off the table.

Janet Hannon: The very bottom of it is, if you can see it, it's just glass. It's smooth as glass because it slides down to that smooth surface.

Stan Mroczkowski: So you know it's sliding right but you don't want that gas to go away. It's a good idea to put it in an air-tight container. Oh, not really. Cause when it's sliming, it's really not going to stop. So we store dry ice in containers that breathe as you see here.

We can see, it is very cold. Here we go. Everyone can see that. If you can try this dry ice.


Janet Hannon: So how does that happen?


Stan Mroczkowski: Subliming. Sublimation. There we go. 

Audience 17: What happened to the...?

Stan Mroczkowski: Yeah, actually... 

Janet Hannon: This is a big balloon, don't worry. It's not going to pop.

Stan Mroczkowski: Let's let go. All right. 

What are the other unique properties, carbon dioxide, as compared to all these other gases we've been showing you, is that when it dissolves in water, it will react with the water to create what we call the weak acid solution.

I don't know if the students here have learned about acids and bases, but we measure acids and bases on what's called the pH scale. Maybe some of you have seen this. It runs from 0 to 14. Acids are below pH 7, so from 0 to 7, and bases are above 7, 7 to 14. And very importantly, 7 itself is neutral.


All right, what are some common acids? I think we all know some common household acids. Lemon juice. Lemon juice is an acid. It has a pH on this scale of about 2.3, so it's pretty far down here. Even further down, a stronger acid is battery acid inside your car, the sulfuric acid inside the battery. It has a pH of about 1.

The neutral, basically one of the only things that are neutral is pure water. Pure water. Absolutely nothing else in it has a pH of 7.0. 

As far as bases, a baking soda solution. Baking soda, you can find that at home. If you dissolve that in water, that will be basic, about pH 8.4. Milk of Magnesia, like antacids, pH 10.5. Working our way up even further, liquid drain cleaners. Liquid drain cleaners, extremely basic pH of about 13.2. That's why you should never, ever touch that with your bare hand.

OK, but right now, what we're most interested in is what happens when carbon dioxide dissolves in water. I'm sure you've all tasted this at one point. Carbonated water, seltzer water, pH of about 3.8.

OK, I told you that, but you probably know that you can create an acid solution. In order to do that, what we can use are chemicals called indicators. An indicator is a compound that turns one color in acid a different color and a base. So a different color depending on the pH. 

Let's see, looking out here. I actually have four solutions and I've added a little bit of base to each of these, so all these solutions are basic solutions. All basic solutions have a high pH, a pH above 7.

What I've used was the chemical again in our lab, that's kind of a main ingredient for... but it's a very, very diluted solution.
This one here is called thymol blue. I'll grab some chunks here. OK, basic solution. We know if CO2 is dissolved it will turn acid, so we get some of this CO2 dissolved in there. What should I... oh, I'll just drop it in.

What's happening in there, as it's sliding away, you can see it bubbling and bubbling, then it's turning acid.

Everybody see that? Now it's a slightly acidic solution. So thymol blue is an indicator that goes blue in a base to go, and that's...

Audience 18:  So what happened to it... yellow?

Stan Mroczkowski: What's that?

Audience 18: After you put in yellow?

Stan Mroczkowski: It will just stay. If you started this acidic and put the dry ice in here, it will just stay on.
Now here's one that's yellow, but it's a different indicator. It's called methyl red. It starts out yellow in our basic solution. What color do you think this is going to turn? I think I pretty much gave it away by the name. We'll see.

Janet Hannon: It doesn't happen immediately. The carbon dioxide has to go in the solution.

Stan Mroczkowski: All right, now now. So methyl red turns the red and red-orange in color.


OK, moving on. This one is my favorite. It's called phenolphthalein. Beautiful magenta color. Let me grab a chunk here. Phenolphthalein. What do we think here, feel like magenta? Do you think it could...

Janet Hannon: Guesses. We need some guesses.

Stan Mroczkowski: There we go. Let's just find out. We're getting really close. I want you to shout out the color while it's turning. This one shout out the color!

Janet Hannon: Where?

Stan Mroczkowski: Oh, yeah. Clear is the color an acid solution, so it's clear.
All right. And this last one here, this last container, this is like the rarest indicator of all. It's called Brassica oleracea . Anyway. Has anybody heard of this? It's very rare. No, it's not. It's red cabbage.



Stan Mroczkowski: We just sliced up some red cabbage, boiled it for about 10 minutes this morning, just drained it off. You can do this at home. And you can use baking soda for your base solution, lemon juice for your acid solution.
This one here is actually really, really fun. I'll turn so you can see. Stir in the compound there. All right. So it's starting out as a nice brilliant emerald green. It doesn't take forever.

Janet Hannon: If you want shows where you see they go in the chemistry lab.
Audience 19: Red!

Audience 20: Purple!

Stan Mroczkowski: Yeah, it's turning purple.

Janet Hannon: But they think that all chemists do nothing but have these witches brews, cause that's how they do it.


Stan Mroczkowski: OK. Yeah. So red cabbage turns... actually, it didn't quite work as well here as a lot earlier we did it, it actually, on its very basic, it's a phenol green. And if you noticed how it very quickly transitions sort of blue to this more purple-pink, then as you keep going and make it more acidic, it will turn red. But right now we're stopping at pH 2.8. We're not going down to the pH of say battery acid. No that's way, way, way, way too much.

Janet Hannon: This is minus 78 degrees, but there are times in the lab when we need something really, really cold. And then...

Stan Mroczkowski: Give us a moment here to move these out of the way.

Janet Hannon: We bring out what I like to call 'the big guns'.


Stan Mroczkowski: Oh, this looks good.

Janet Hannon: Oh, there's one more thing we can do. One more thing we need to do with the...Remember we said carbon dioxide weighs more than air, is heavier than air? So what do we need for a plane to burn? What gas do you have to have for a flame? Oxygen? This bottle still has dry ice. The whole bottle is full of carbon dioxide. Since carbon dioxide is heavier than air, it pushes all the air out.
So this is a bottle of carbon dioxide. I'm going to pour it out. And it should pour because it's heavier than air.
Stan Mroczkowski: There we go.



Janet Hannon: And in fact, when we're in the lab, we can't get a beaker and put it on one of our balances and pour this into the beaker and you see the weight going... Anyway, it shows all its weight on the balance.

Stan Mroczkowski: That's the big gun.

Oh, and incidentally, we passed by on the chart the molecular weight of gases, but Janet just said that of course CO2 is heavier than air. If you remember its molecular weight of 44, there's one gas, a dangerous gas, that's even heavier than that, and that's radon. If you've ever heard of radon, it's a problem in basements. It collects down the basements. It has an atomic mass of 222. So compared to air, it's about nine times heavier. So that's why it settles in your basement needs special ventilation systems to clear it up.


OK. So minus 78 below zero. There are actually times in the lab where we really have to get a lot lower than that. So who are you going to call? Liquid nitrogen. This is how it's delivered to the lab. It's in a big Dewar, what we call the Dewar. It's essentially a high tank thermos and stands about yea high. Liquid nitrogen, which is everybody's favorite.

Janet Hannon: Can you see the hose coming down there? You take that hose and you open it and put it into a smaller harness. That's what this is. This is a thermos that will go back.

Stan Mroczkowski: So this goes right here. We have some valves up on top. Turn it open just like a hose, but instead of water coming out, liquid nitrogen.

Janet Hannon: Can you see it? No, it's just nitrogen. It will not explode. But can you guys see it? It just looks like water. It's just clear liquid. What is all the white stuff that's coming off?


Audience 21: Vapor!

Janet Hannon: What kind of vapor? 

Audience 21: Water vapor.

Janet Hannon: Excellent. That's very good. Because the liquid nitrogen is so cold that it boils as soon as it hits the air, as soon as it gets to this temperature. It boils, but when it boils, it's still very, very cold until it mixes with everything else. So on a cold day in the lab when you breathe, can you see the water vapor? That's what this is doing is the Liquid nitrogen is so cold that it's condensing the water right out of the air.

Stan Mroczkowski: Yeah, well this is liquid nitrogen.

Janet Hannon: I don't know. What is liquid nitrogen?

Stan Mroczkowski: OK. So dry ice, throw some carbon dioxide which is 78 degrees below zero. The Liquid nitrogen has got to go all the way down on the Celsius scale, 196 degrees below zero, 
Fahrenheit is 321 degrees below zero.


It's actually a little bit colder than oxygen. oxygen's boiling point is 183 below zero Celsius, and liquid nitrogen sits at 77 degrees above what we call absolute zero, the theoretical coldness anything can get.

Janet Hannon: The neat thing about Liquid oxygen is that it's blue. It's robin's egg blue. And we had actually made it in the lab. We have to obtain something you condense the oxygen from the air, you've got liquid nitrogen. And you can see it.

So these are balloons that I blew up in the lab. They're just regular balloons; just plain old air, nothing.

Stan Mroczkowski: Well, yeah, breath. Breath.

Janet Hannon: Yes. So what's in your breath? When you breathe out, when you blow up a balloon, what's in here?


Audience 22: Carbon dioxide.

Janet Hannon: Yes. What else? Water. Water vapor. What else?

Audience 24: Oxygen.

Janet Hannon: Oxygen, because you can use up all the oxygen in one breath. What else?
Audience 25: Nitrogen.
Janet Hannon: Nitrogen! Yeah, this is a gas. And what about argon? There's argon in here, there's krypton, neon, xenon, and all those things. Hydrogen and helium. Anything that's in the air, and the only thing your body uses is the oxygen. Everything else comes back out again.

Stan Mroczkowski: So I have our Dewar here and a thermos of liquid nitrogen. How many of these balloons do you think we can get down in there? Say one, two, or about four. No. Well, let's try again. Let's see what happens.


Audience 26: Will it explode?

Janet Hannon: It will not explode.

Audience 27: It's melting

Janet Hannon: It's not melting, it's shrinking. But why?
Audience 27: Because it's cold.

Janet Hannon: Because it's cold. But why is it shrinking? What's happening to the gases that are inside these balloons?

Stan Mroczkowski: Start with the water vapor.
Audience 29: It's evaporating!

Stan Mroczkowski: The water vapor there, that freezes at zero degrees, right? We're down here at minus 196. Well, that's frozen. carbon dioxide? Well, that's frozen at minus 78 degrees C. So that's frozen. The oxygen in the balloon, condensed. Condensed to liquid.
And then the nitrogen is actually, this is a good demonstration of something in chemistry we call Charles' Law, which basically says that the volume of a gas is heavier. So if you have lower temperature, you have a smaller volume. So the nitrogen is going to get smaller and smaller.

Janet Hannon: The molecules are moving slower and slower.

Stan Mroczkowski: Because they're getting closer and closer together. That's just...

Janet Hannon: As some of the liquid nitrogen is being forced out, it cools down to the water vapor that's in the air all around you.. What you're seeing is water vapor, fog.

Stan Mroczkowski: Yeah. You sort of localize the atmosphere right here, it's extremely cold. Whoa, I think we got one on the floor.

Janet Hannon: We did. 

Stan Mroczkowski: The...


Janet Hannon: No.
Stan Mroczkowski: What's that?

Janet Hannon: No.

Stan Mroczkowski: Well, sure enough. All right.

Janet Hannon: And we probably could get more.

Stan Mroczkowski: Yeah. So what do you think is going to happen when we pull it out?
Janet Hannon: What would happen?

Audience 31: It's going to get bigger again!

Janet Hannon: It's going to get bigger again. What else? What? What do you think? All right.

Stan Mroczkowski: All right. Let's find out. Here you go.



Stan Mroczkowski: So what happened? We had Liquid oxygen in there, it turned out from a gas. The nitrogen that was very soft because of the cold warmed back up and expanded again. You see how carbon dioxide in there sort of backed the gas. And the water vapor well.. turned back to gas and water.

Janet Hannon: And the reason that they break is because it warms up at different rates, and 

sometimes it will warm up too much and it will just expand out too much.

Stan Mroczkowski: Yeah. Don't worry about that. These are brand-new one, but they shouldn't all be like this. So proof of the putz.

Janet Hannon: But when we did this at the science camp, all the times we use the same balloons over and over and over again for almost five to six times, and they just keep... If it's a good balloon, you can do it more than once.

Stan Mroczkowski: Yeah. All right. So both of you.


Janet Hannon: What's in here?

Stan Mroczkowski: Oh, what's in here? 

Audience 33: Oxygen.

Stan Mroczkowski: No. It's on this bottle.
Audience 34: Carbon dioxide.

Stan Mroczkowski: Carbon dioxide. So what's going to happen here? All right.
So now, we saw when we took a breath balloon out, it started coming back really fast and then popping and pulling. If we take this one out now, do you think it's going to come back as fast, faster or slower? 

Audience 35: Slower.

Janet Hannon: Why?

Stan Mroczkowski: All right, let's find out. It's a lot slower. But why? Because the carbon dioxide, if you think about it, it's going to warm up to 78 degrees below zero before it turns back into a gas. So it's struggling to get there.


And in fact, I think someone said we have a chunk of dry ice, that's absolutely right. So there it is.
So what did we do? We went from dry ice, dissolved carbon dioxide into gas, back to a solid, and now, a couple of minutes, a couple of seconds, and then back to a gas. At that temperature, carbon dioxide is a gas.


Stan Mroczkowski: A few more things to show you. I think we have a little more time.

Janet Hannon: Now we're going to the portion to show you.

Stan Mroczkowski: I say we sacrifice this?


Janet Hannon: Yes.

Stan Mroczkowski: Well, someone always asks, no one here is asking, we always get the question, 'Put your hand in there?' Well, we'll show you what we basically what happens if you put your hand into liquid nitrogen.


Janet Hannon: Yeah, yeah. I know you can't see this, but if you could see it, it's boiling like the flower in here, because the flower is at room temperature and this is minus 196 C. The flowers, they look the same.
Stan Mroczkowski: There you go.

Janet Hannon: So what happens is it breaks down cells in the flower. It destroys the cellular structure and... There are some things that can grow back. Like a rubber band.



Stan Mroczkowski: So let's use a rubber band. It's screaming down on there.

Janet Hannon: After this is over, we're going to put more rubber bands in there and you guys can come up and stamp on them. That's fun.

Stan Mroczkowski: All right, one more thing. Here, this is actually a pencil. It slows the natural...


Here we go. I'm going to toss it up to the ceiling. Oops, a little too high. I'll try it again. All right. It comes up to about here. Let's see another one. Let's get it pulled in. If we douse it with liquid nitrogen, I'll toss it up again. See the solid rubber band, it's got to be stiffer, right? So do you think that will make it bounce higher?

Audience 37: No!

Stan Mroczkowski: Do you think it's going to bounce a little lower?

Audience 37: Yeah!

Stan Mroczkowski: Let's find out. 

Janet Hannon: Now they're getting all the stuff in the liquid nitrogen is boiling because it puts something into a much, much warmer air. And the reason Stan put that glove on his right hand, because that, especially inside gloves for nitrogen.

Stan Mroczkowski: OK, so we bounced about all the way up here. I want you guys to watch this really closely, OK?


Stan Mroczkowski: This looks good bounce. It's usually quite difficult to take the rubber...



Janet Hannon: The first time I ever saw this was in my first year at chemistry class in college, and the professor who was, that's what we taught first year chemistry, he was so good at it. And you have to imagine a lecture hall almost this big. He took the ball ] and he threw it across 
the lecture hall. And it was just so dramatic. It was wonderful.

Stan Mroczkowski: I actually didn't see it in the slides. If any of you who are roughly my age, remember when... and they showed it on there. And I remember to this day, I actually teach it.


Anyway, I just wanted to give a plug for next month's lecture. I think that's all we have, so thank you all.

Janet Hannon: Wait, wait, wait, wait. I have a couple of acknowledgements. I would like to thank Jacob Goldblum, who is our boss who gave us the time to put the presentation together, because this is not what the taxpayers pay us to do.


Janet Hannon: We use these tools, but this is not what we do all the time. And I'd like to thank Stan because it is such a pleasure to have him do this with me, just...


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