Chemistry: Matter and ChangeChapter 15: SolutionsIn the NewsHoney in Water (in Space)September 2004Try 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: University of Southern Mississippi Marketing and Public Relations: Marshall Spaceflight Center: |  |
