Chemistry: Concepts and Applications

Chapter 13: Water and Its Solutions

In the News

Honey in Water (in Space)

September 2004

Try This One Yourself

Want to go hands-on right now and see something that puzzles chemists? All it takes is a squirtable honey bottle and a tall glass of water. Warm the honey up until it's able to flow smoothly through the spout. Now squirt a blob of honey into the water and watch it fall. What do you see?

What you will notice is that the honey does not fall like a rock. Instead it twists, turns, and cavorts into all kinds of unusual shapes. It's almost frustrating that you only get a second or two to watch the honey waver around before it plops to the bottom. If only you could suspend it in the water, somehow, so that it would go through its strange shifting movements without ever hitting the bottom of the glass. Then,you could study its motions carefully and figure out what causes the honey to fall. But how on Earth could you do that?

Answer? Not on Earth at all.

Chemistry professor John Pojman of the University of Southern Mississippi was interested in this phenomenon, and he had an excellent idea for how to keep the honey suspended in the water. Run the experiment in space-on the ISS, or International Space Station.

The fact is, the way fluids mix has only been studied in one place: the surface of Earth. That's obvious, but doing all your chemistry on Earth's surface has its limitations. The big one is that we're standing at the bottom of what scientists call a “gravity well.” The gravitational pull of the Earth is quite strong where we are, which in some ways, is a good thing. It's why your beakers and test tubes stay on your work bench. However, Earth's gravitational pull has a profound impact on the way fluids behave.

For example, in the experiment you just ran by squirting honey into water, the motion that was most obvious in the honey was one you probably ignored: straight down. That's because dense fluids, such as honey, sink through less-dense fluids, such as water. Every other motion the honey went through was more or less overshadowed by that one motion.

But that's only true in a gravity well. On the space station, which is in orbit high above Earth, the honey would not sink. Then, other forces at work between the fluids could be seen more clearly-such as whatever makes the honey do its wobbly dance.

Is This Important?

Chemists are not sure what those forces are yet, but differences in composition, temperature, and subtler forces acting between molecules will presumably all play a part. Still, you might be asking why we should do this work. It's kind of cool to watch honey wobble around, but is understanding how fluids behave in zero gravity really important?

Sure it is! As Professor Pojman points out, we are going to be manufacturing things soon in space, especially if we plan to send people to far-off locations, such as Mars. The trip takes so long, and is so complicated, space travelers will have to make things onboard their ships rather than packing everything they might need before leaving Earth.

What about plastics, for example? Chemists on Earth make plastics by putting together various fluids and powders and then heating the mixture. This is done every day on Earth, and we know how to do it well. Will this mixing and heating work in space, though, or will the forces that gravity usually keeps at bay change everything? We don't yet know.

Houston, We Have Honey

Professor Pojman isn't an astronaut, though, so he could not go to the space station himself. Instead, he designed an experiment the astronauts could do for him, called the MFMG Experiment, for “Miscible Fluids in Microgravity Experiment.” (Miscible just means they can be mixed.) Guess what high-tech devices were involved? A syringe and a plastic tube. Guess what space-age fluids were mixed? Honey and water.

Yes-just this year astronauts onboard the International Space Station did a more controlled repeat of the very experiment you just did with a glass and a honey bottle! They videotaped the results and sent the images of swirling honey back to Earth for chemists to ponder. The ultimate goal is to understand how industrial fluids will or won't behave when mixed in space.

Activity:

You have already seen the strange honey-water effect that has chemists wondering about how different fluids will mix in space. Don't just settle for one shot, though. Instead of a blob of honey, try squirting a stream this time. Try moving the nozzle as you squirt the stream. Try it in cold water. Think of different fluids you could use instead of honey. What effects do you see?

NASA:
http://science.nasa.gov/headlines/y2004/09apr_tea.htm:

University of Southern Mississippi Marketing and Public Relations:
http://www-dept.usm.edu/pr/prnews/jan04/pojmantest04.htm

Marshall Spaceflight Center:
http://msad.msfc.nasa.gov/matsci/proj_mfmg.html

Looking Forward to the Past

March 2005

A lot of scientists--and smart people in general--are concerned about global warming. That's the trend toward increased temperature our planet is experiencing, largely as a result of things we humans do. Burning fossil fuels, such as oil, puts chemicals into the air which change the atmosphere. Gradually, this changes other things, too, from how high or low the oceans are to how strongly the winds blow to plenty of things we don't yet understand.

How might the climate react if we keep on affecting the atmosphere the way we are? Scientists would like to know--but how can they predict the future?

Actually, there are ways. One way is to look into the past.

Deep Ocean Cores

In order to help them think about these issues, chemists at the University of California, San Diego and Stanford University have managed to look back into Earth's past . . . 130 million years back, in fact. They wanted to see what things were like during previous periods in our planet's history in order to get a sense of how the climate changes. How can you examine the ancient past without a time machine? By drilling up deep ocean cores.

Ocean cores are long, thin rods of matter drilled from the floor of the ocean. If you've ever cored an apple, you have a sense of this process already. You insert a tube-shaped blade into the apple, push it all the way in, and pull out a long, thin section. It's the same idea here, although ocean cores are much larger than an apple core.

Cut the Cake

Once the cores have been brought up to the surface, they can be examined for the presence of various chemicals at different spots. Why do that? Because the floor of the ocean is like a time capsule: since sediment is laid down across time, the deeper you dig, the older the sediment you're seeing.

Imagine slicing into a big birthday cake and then examining the side of the slice. You'd see layers. The bottom layer was made first; then some icing was put on it; then another layer of cake was added; and so on. So the bottom of the cake is older (by a few minutes, anyway) than the top of the cake. Deep ocean cores are like that, only the very bottom is 130 million years older than the top!

Quest for Sulfur

These chemists were especially interested in the presence of sulfur along the cores they dug up. That's because different types of sulfur are laid down on the ocean floor under different conditions. A lot of sulfur of a particular type *here* means there were volcanoes going off during *this* period (and chemicals they blasted out eventually sifted into the oceans); a lot of sulfur of another type *here* means lots of continental weathering was happening during *this* period, and so on. By learning these things, the chemists could infer what the atmosphere on Earth was like at different times, how long those conditions lasted, and more.

Quick Changes

What does this have to do with global warming? By looking into this long-buried record, the chemists were able to see when climate changes have occurred in our past. Were oxygen levels going up or down? Were the glaciers freezing or melting? When? For how long? Once they knew these things, they had some direct evidence on which to base their theories of how the climate behaves.

One of the more sobering insights the researchers gained from this work is that things can happen pretty quickly. That means the changes we are causing to our planet's atmosphere--which are already making the glaciers melt, for example--may have serious effects sooner than we had anticipated.

“Some relatively rapid changes can happen on Earth,” says Adina Paytan, the first author of the report that came out in Science magazine in June. “So we have to be prepared.”

Activity:

If you have access to a refrigerator (other than the one your family uses!) that has a dial for setting the temperature, ask your parents whether they will help you with an experiment using it. Try keeping some food items in this refrigerator for a week, taking notes on how well it preserves things. Next, then turn the dial down by one degree for one day, and see what happens. You wouldn't think that a one-degree change would make much difference, but does it?

Take more notes, examining everything in the refrigerator before and after you change the temperature. What has been affected? What surprised you? (If you have liquids in your refrigerator, be careful--liquids expand when they freeze and can break out their containers, leaving you with a goopy mess.)

UCSD:
http://ucsdnews.ucsd.edu/newsrel/science/mccretaceous.asp

Science Magazine:
http://www.sciencemag.org

Paytan Chemical Oceanography Lab:
http://pangea.stanford.edu/research/paytanlab/adina.html

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