Cracking The Cool Science Of Ice With winter storms continuing across the country, much of the nation may not currently have warm feelings toward the solid form of water. Physicist and water researcher Eugene Stanley and Mariana Gosnell, author of Ice: The Nature, the History, and the Uses of an Astonishing Substance, discuss the cool, slippery science of ice.

Cracking The Cool Science Of Ice

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


You're listening to SCIENCE FRIDAY. I'm Ira Flatow.

Events are still unfolding in Egypt following the resignation of President Mubarak. NPR News is following the situation, and we will update you with the latest throughout the program, should it become necessary.

Also, later this hour: Are you being overdiagnosed? But first, this just in: It is still winter. And it's been one hell of a winter for much of the country. We're only halfway through the season, but I'd like to share with you something personal, a view about all of this snow and ice that may make you actually smile while you're shoveling that white stuff or nod your head in agreement and wonder why you're slip-sliding away down the driveway.

And what I mean to say is that there is something - to me there's something very magical about water and what happens to it when it freezes. I don't think there's anything else in the world, perhaps in our universe, that is quite like ice.

So we're going to begin this hour by talking about ice, and as we talk about ice, I am hoping you will look at in a different way and see that it is really, really cool, so to speak.

Give us a call. Our number is 1-800-989-8255, 1-800-989-TALK. And you can tweet us, @scifri, @-S-C-I-F-R-I. And we'll be talking about ice and how to enjoy it more for the rest of the winter.

Let me introduce my guests. Eugene Stanley is director of the Center for Polymer Studies in the Department of Physics at Boston University. He joins us by phone. Welcome back to the program, Dr. Stanley.

Dr. EUGENE STANLEY (Director, Center for Polymer Studies, Department of Physics, Boston University): It's good to be back, Ira. Thank you for inviting me again.

FLATOW: You're welcome. Mariana Gosnell is a freelance science and health writer. She was a reporter for Newsweek for many years. And she's author of the book "Ice: The Nature, the History, and the Uses of an Astonishing Substance." She's with us here in New York. Welcome to SCIENCE FRIDAY.

Ms. MARIANA GOSNELL (Freelance Science and Medicine Writer; Author, "Ice: The Nature, the History, and the Uses of an Astonishing Substance"): Thank you.

FLATOW: Why, to you, is this such an astonishing substance? What's the most astonishing about it?

Ms. GOSNELL: Well, it has a lot of very contradictory qualities.

FLATOW: Such as?

Ms. GOSNELL: We have - it is more brittle than glass. It can flow like molasses. There are parts of the world where there's ice that's a million years old. And yet you can look at the sidewalk and see a puddle and see it come and see it go.

That's because ice is very near its melting point. You think of it as being the ultimate in cold things, and actually, it is, in its own terms, hot. It's within 50 degrees of its melting point, which accounts for some of the strange things we see it doing.

In addition to that, it floats. I sort of took that for granted, but not very many substances do that. When they get colder, they get heavier, and they sink.

FLATOW: It also expands when it's freezing, like other substances contract, right?

Ms. GOSNELL: Right, and that's why it's floats. It's got - I'm sure Dr. Stanley can tell you a lot more about that.

FLATOW: Okay, Eugene, you're up. What makes it so amazing to you?

Dr. STANLEY: I think the most remarkable thing about ice, in my opinion at least, is that it occurs in many, many, many different forms. Most solids occur in typically one or maybe two or three different forms, and ice has approximately 15 different crystal forms, as well as two forms that are called amorphous, which means without any shape at all.

And these amorphous forms, for example, are found naturally on comets, on asteroids, and the crystalline forms are found on Earth or at least could be made on Earth with enough pressure. Nothing else does this.

FLATOW: Wow. Is it true that ice is a mineral, it's a rock when - water, when it freezes, actually becomes a rock, it's classified as a mineral? Or is that something I just picked up someplace?

Dr. STANLEY: It depends how you define mineral. But normally, you would not call ice a mineral.

Ms. GOSNELL: But you wouldn't call it a rock, either?

Dr. STANLEY: I wouldn't call it a rock because it's - it depends how you define rock.

(Soundbite of laughter)

Ms. GOSNELL: Okay.

FLATOW: But - and it's hard as a rock, could be harder. It could do real damage. Look at the Titanic, things like that, when it...

Dr. STANLEY: Exactly. But the damage of the Titanic goes back to the point that Dr. Gosnell just mentioned, namely that ice floats. But it doesn't float all on top of the water, like the Titanic boat did. It floats only 10 percent on top of the water, and the other 90 percent is hidden beneath the water.

And therefore, the Titanic and submarines ever since have to worry about the damage that hitting ice could cause to their vessels.

FLATOW: So what happens physically as the water cools down? How does the water transform into ice?

Dr. STANLEY: The principal reason it transforms is that water is a collection of molecules, H2O, every child learns that. And these molecules are stabilized, or, if you will, held together one to the other by a kind of bond called a hydrogen bond.

And that bond has the property that as the bonds get stronger when you cool water, the ice expands. And the reason that happens is that the structure of ice is not what we learned in school, just a boomerang with the tips of the boomerang being the two H's and the middle of the boomerang being the O.

But instead, it's a complicated pyramid shape, if you will, like the Pyramid of Gaza, if you could imagine that pyramid, with an oxygen in the center of the pyramid, where the mummy might lie, and two positive charges for the H's but also two negative charges in the other corners of the pyramid.

So it's a complicated, three-dimensional, charged object. And one can pack these things in many different ways, a little like playing the child's game of jacks, where those complicated little objects can be thrown together in all different ways.

If you imagine there were bonds between them, you might get a very low-density structure, a very big-volume structure, it would be like a jungle gym. But if on the other hand you broke all the bonds, if you sawed the bonds of a jungle gym, the whole thing would collapse into less space.

So the sawed jungle gym or the broken-down jacks are the analog of the water, and the glued-together jungle gym is the analog of the ice, lower density. So the more you cool it, the more expands.

FLATOW: Interesting. Mary, did you want to say anything to that?

Ms. GOSNELL: I just want to say that one of the most thrilling things I have ever seen is to see a lake, a portion of a lake, that very, very thin, top layer turn to ice. I saw that in New Hampshire, and I expected it just to, you know, turn into something that looked like, you know, painted glass or something.

Instead, it had so many patterns, so many needles and lumps and beveled areas and incised. It was a work of art.

FLATOW: It didn't look like glass. It did not look like a sheet of glass.

Ms. GOSNELL: No, it looked the most richly varied kind of tapestry or something. I was terribly surprised.

FLATOW: Let's go to Pace(ph) in Boone, North Carolina. Hi, Pace.

PACE (Caller): Hi, how are you doing?

FLATOW: Hi, there. Go ahead.

PACE: Okay. Well, I am an ice climber and enjoying the ephemeral ice that we do here in the Southeastern U.S. We get to climb on many different types, and there - it can be anywhere from very cold and hard ice that we would call brittle, to a soft, slushy form.

However, the best ice for ice climbing is what we could call plastic ice, where your picks will sink very nice and firmly in there with just one swing of the axe.

Ms. GOSNELL: I can imagine that there's almost no better way to get a good luck at ice than being a few inches away from it and hanging by, you know, a couple toe picks and, you know, ice picks.

FLATOW: That's heaven.

Ms. GOSNELL: You think so? Do you do that?

(Soundbite of laughter)

FLATOW: No, I love ice - you know, when I was in Antarctica many decades ago, I got to see a lot of ice. And the one thing that impressed me -because I love to talk about ice - is that it has a color.

Ms. GOSNELL: Oh, many.

FLATOW: It's blue. I mean, if you see big - it's almost like looking at the ocean or the sky. The light is refracted in it. So it's actually big, big sheets of blue, which I didn't expect.

Ms. GOSNELL: Well, it can also be a little greenish and nearly black, blue-black, and very white.

FLATOW: Stanley, have you seen different colors of ice?

Dr. STANLEY: Indeed, indeed. And the different colors again refer to the fact that those little jacks, if you want to call them jacks, those little pyramids, can be packed together in all different ways. And depending on how they're packed together.

If you Google blue ice, as I did just while your caller was asking his question, you see some beautiful pictures of exactly what Mariana Gosnell said, ice covering a lake.

FLATOW: If you go to our website at, Dr. Iacovino is on there. She went to Antarctica and went through the ice caves there, and she brought back some gorgeous pictures of the blue ice there. You can see it on, all those gorgeous photos in her blog.

Dr. Stanley, let's talk about ice for a minute. Do you think that people don't have a good enough appreciation of what they're looking at when they look at ice? They just think: Oh, gosh, this is something I have to put up with?

Dr. STANLEY: Yes. Mainly, of course, if you're not an ice climber, where you really need ice, for most people ice is a damn nuisance. And we just can't wait for it to all melt.

And it's always a remarkable fact that it takes so long to melt because the temperature of the air can be well above the freezing point, and the ice is still solid there. So for most people, that's the experience.

However, ice is remarkable in many other ways. A simple experiment one can do at home is to add salt to an amount of water in different concentrations. For example, one can mimic the concentration of the ocean, or one can make it even saltier.

And then first of all...

FLATOW: Hang on to this experiment because we're going to run out of time.

Dr. STANLEY: Okay.

FLATOW: And we'll come back and talk about that. I'm sure it has something to do with making ice cream here.

(Soundbite of laughter)

FLATOW: How do you get ice cream to freeze and lower the freezing temperature of the water. So stay with us. We'll be right back, talking about ice with Eugene Stanley and Mariana Gosnell. Our number, 1-800-989-8255. You can tweet us, @scifri, @-S-C-I-F-R-I. Tell us what you like most about ice. Stand by. We'll be right back after this break.

FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

(Soundbite of music)

FLATOW: You're listening to SCIENCE FRIDAY. I'm Ira Flatow. We're talking this hour about ice and the amazing properties of this frozen water.

My guests are Eugene Stanley, director of the Center for Polymer Studies in the Department of Physics at Boston University; Mariana Gosnell, author of the book "Ice: The Nature, the History, and the Uses of an Astonishing Substance." Our number, 1-800-989-8255. You can tweet us @scifri, @-S-C-I-F-R-I.

And when I rudely interrupted Dr. Stanley, he was talking about an experiment you can do with mixing ice and salt water, water and salt. And what do we do with it then?

Dr. STANLEY: Put it in the freezer and watch it freeze. And you'll see, if you have a thermometer also there, that the temperature at which it freezes depends on how much salt you put on it. If you put in the amount that corresponds to ocean, which is about three percent, the temperature will be only three degrees lower than the normal 32 Fahrenheit. It'll be about 29 Fahrenheit.

But if you go up to, say, 10 percent, then it'll be three times as low. It'll be, instead of three degrees lower, it'll be about 10 degrees lower. Okay, that already shows that the presence of the salt inhibits the freezing because the water molecules want to form a crystal, but that salt is in the way.

But the even more remarkable thing is that the salt does not join the frozen water, and you can do that by just tasting the water that's leftover, and it'll be very, very salty because the ice crystal itself is almost free of salt, whereas what's leftover is the salt was there, it has to go somewhere, so it just stays in the water. It's left behind.

FLATOW: So can you purify saltwater, then, by freezing it?

Dr. STANLEY: You definitely can.

FLATOW: So the salt will drop out of the water, you'll have...

Dr. STANLEY: Exactly.

FLATOW: A snow cone.

Dr. STANLEY: It won't be perfectly salt-free, but it'll be pretty much salt - so if you're stranded, Ira, sometime on one of your glaciers on Antarctica, and you're thirsty, don't be afraid to melt a little bit of an iceberg and have a taste. It won't be too salty to eat.

FLATOW: Well, I actually fell off one. It was a small, it was a low-lying glacier. I was trying - I put my microphone on the ice to listen to it melt in the sun there, and I was sliding backwards as I was - and I saw the ground was coming up very quickly, and I flipped over.

It all ended well, but it also reminded me about the debate - is there not a debate about why is slippery? Mariana?

Ms. GOSNELL: There was one. I mean, people used to - everyone used to say it was because of pressure melting, the weight of your body on this thin blade. But that was - they determined that you couldn't possibly put that much pressure in the weight of your body.

And then they started to talk about a quasi-liquid layer that's always on ice, and that is what lubricates it. And then they decided it was much too small to affect that.

So the current thinking is that it's friction, just the frictionless qualify of ice is from the friction of the blade or whatever.

FLATOW: That doesn't sound very scientific, just friction. When I drag a block on the ground, it's just friction, but it's not slippery.

Ms. GOSNELL: I think at the other ends of things (unintelligible), really cold and really dry, you're in trouble.

FLATOW: Eugene, you have any weigh-in on that?

Dr. STANLEY: Yeah, it's roughly the right answer. But it's also true that I think everyone knows this who's in a really cold place, when the temperature outside is, let's say, below zero Fahrenheit, you're not going to fall down on the ice nearly as easily as when it's a lot more near the freezing point.

FLATOW: 1-800-989-8255. Let's go to Drew(ph) in Fort Wayne. Hi, Drew.

DREW (Caller): Hi, how are you doing?

FLATOW: Hi there.

DREW: I just wanted to make a comment and take some reactions on the fact that you've already stated, that ice is a rock. People do take it for granted.

I mean, you look at planets - Venus, Titan, Europa - all these planets have a molecule that freezes and melts, and we're just another part of the universe, I guess you could say, that has this hard substance, I guess. And we're in the habitable zone, I guess, far enough away that it freezes and close enough that it can melt. And we're just one people that's, I don't know, that can experience this.

FLATOW: All right. You've made your point. Thanks for calling.

DREW: Yeah.

FLATOW: 1-800-989-8255. But let's talk about some of the mythology of ice in the few minutes we have left. What happens in the freezer to the ice cubes? Where do they go? I mean, you put ice cubes in the freezer, and suddenly, a few weeks later, they're not there anymore. Where did the ice go? Dr. Stanley?

(Soundbite of laughter)

Dr. STANLEY: I never had that experience.

(Soundbite of laughter)

FLATOW: Is that right?

Ms. GOSNELL: Martinis. It depends on how many martinis you drink.

Dr. STANLEY: Just take them out in the middle of the night for a drink and forgot?

(Soundbite of laughter)

FLATOW: I'm telling you, and our listeners are going to call in, and they're going to back me up on this.

Dr. STANLEY: Okay, okay.

FLATOW: So the ice ablates, right? Doesn't ice ablate? Doesn't it...?

Dr. STANLEY: It's sublimation.

FLATOW: It goes away. Without turning to liquid, it evaporates. Doesn't it to that?

Dr. STANLEY: That is correct.

FLATOW: So then why is - you're looking at me like I'm crazy.

(Soundbite of laughter)

Dr. STANLEY: We wouldn't think an entire ice cube could sublimate away.

FLATOW: Oh, yeah. Well, you don't leave them as old in there - not as old in your refrigerator as they are in mine. But, you know, you have that - also, the freezer comes on with the blower in it. So it's blowing air over it, also.

Ms. GOSNELL: Your freezer.

Dr. STANLEY: Ah, you have a different story, yeah.

Ms. GOSNELL: I was thinking when you were talking about enjoyment, all those people who go ice fishing, you know, and there's a lake in Minnesota where there are 65,000 ice shacks out on the lake. And that is, you know, a serious contribution to the happiness of a lot of particularly men who want to go out and be away and dig a hole in the ice and...

FLATOW: But it also illustrates that it is good that ice floats, or you wouldn't have the top of the ice - ice would be under the water, and you couldn't put your ice house on top of it, your fishing house on it.

Ms. GOSNELL: Right. Probably if it didn't float, we wouldn't be here because all the northern lakes and rivers would freeze from the bottom up and probably wouldn't thaw. Isn't that right, Dr. Stanley?

Dr. STANLEY: Certainly all the species of life that evolved from creatures who lived in water would not survive the winters. So - and the reason they wouldn't is that those lakes would just freeze solid. But instead, the opposite happens.

The ice on top freezes, and actually, inside the lake, it doesn't even get that close to freezing. It stays at 40 degrees. And the reason it stays at 40 degrees is that ice has a density maximum at 40.

So below 40, the heavier water just sinks to the bottom of the lake and stays there. Nobody's stirring the lake. So it just stays there. You can do that with another little experiment at a cocktail party.

Just simply fill a glass, not with alcohol, but simply with water, but a couple of ice cubes in the top of it and a thermometer. And ask somebody what's the temperature.

And almost everyone learned in school that it's an equilibrium. So the temperature of the water should be roughly 32 Fahrenheit. And you look at your thermometer, and you'll see it's not 32 at all, it's 40. And the only way you can make it 32 is to stir like crazy.

And that's again simply because the water, once it reaches 40, it gets less dense. So any cooling below 40 happens only on the surface.

FLATOW: Interesting. In the minute or two we have left, Dr. Stanley, what do researchers not know about ice that they would like to? I mean, it's been around forever, right?

Dr. STANLEY: Yeah. Well, I mentioned the comets that are covered not by crystalline ice but by a kind of solid water but with no crystalline order, a solid water whose structure is almost the same as that of liquid water. It's as if you captured a liquid water and stopped all the molecules moving.

And that kind of water was only relatively recently discovered, and in particular, it comes in two forms, which my colleague, Mishiba(ph), in Japan recently won the major physics prize of all Japan for understanding.

And what he understood is that the two forms of amorphous ice, it can convert from one to the other by a very sharp phase transition. In other words, you have one kind of ice, and then boom, you have another kind of ice. And this is very remarkable because it relates to the properties of water, which probably also have a similar type of phase transition inside.

FLATOW: All right. We've run out of time. I want to thank you both for taking time to be with us today. Eugene Stanley is director of the Center for Polymer Studies in the Department of Physics at Boston University. Mariana Gosnell is author of the book "Ice: The Nature, the History, and the Uses of an Astonishing Substance." It's a great read for folks of us who love to talk about ice. Thank you both for taking time to be with us today.

Ms. GOSNELL: Thank you. Glad to be here.

Dr. STANLEY: Thank you, Ira. Good to talk again.

FLATOW: You're welcome.

Copyright © 2011 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.