CHAPEL HILL -- Using liquid helium, chemists at the University of North Carolina at Chapel Hill have succeeded in artificially creating the world's smallest pieces of ice.
Don't look for them anytime soon clinking in your tea glass, however. The pieces they made consist only of six molecules of water in flat hexagonal rings, just as ice exists in nature.
The unusual achievement could go a long way toward boosting knowledge of water, that unique and fascinating substance without which no life could exist, the scientists say. A report on the research appears in the Jan. 13 issue of Science. Chemistry graduate student Klaas Nauta and Dr. Roger E. Miller, professor of chemistry, carried out the work and wrote the report.
"Despite the fact that water is so important to us, we still don't have a really good molecular level understanding of it," Miller said. "We can do pretty well with some other systems, but water does interesting things that make it unique and also make it somewhat difficult to understand."
For example, a property of water that is bizarre -- yet taken for granted -- is that unlike almost all other substances, it becomes less dense as it freezes, Miller said. As a result, ice floats instead of sinking. The more normal behavior is for solids to sink in their own liquid phases.
"We know that when it freezes, water forms a unique hexagonal ring structure, which accounts for its low density and the fact that it floats in water," Miller said. "Understanding the hydrogen bonding forces that align the water molecules in this way is our goal."
Doing this in bulk ice and water is complicated by the fact that there are so many molecules to keep track of, he said.
"After all, a single drop of water contains about 100,000,000,000,000,000,000 water molecules," the chemist said. "When we're trying to understand water at a detailed level, having so many molecules is a real problem."