From the first educational cycles, the water cycle is usually taught, as a precedent for later studying the states of matter in science, always framing within conventional contexts.
Due to the peculiarities of water, which have not yet been fully resolved by the scientific community, under temperatures considerably below the freezing point of this element, its behavior has opened the way to reveal new information on its composition.
The secrets of water are evidenced by its supercooled state
Water escapes the logic of other fluids. It is more dense in its liquid state than in its solid presentation. That an ice can float on water is proof of this, easy to patent at sight. However, the background to this phenomenon has been the subject of research for decades.
In 2020, a team of scientists from the Pacific Northwest National Laboratory (PNNL) began an investigation to approximate an understanding of this phenomenon. In an unprecedented gesture, they managed to cool the water to temperatures between -47.6 ° C (190 K) and -7.3 ° C (245 K), thanks to the use of a novel laser cooling technique that revealed the nanoscale changes that the water undergoes. liquid water when supercooled.
“Water is one of the most important solvents we have”noted Greg Kimmel, a chemical physicist at PNNL, in conversation with the institution. “We are trying to better understand how water behaves at interfaces, in confinement and in solutions, how it condenses and crystallizes, and so on.”added.
“As the temperature is lowered, most liquid molecules pack up very tightly and are very dense. But below 39 ° F, the water is just the opposite »explained Loni Kringle, who worked on the research as a postdoctoral researcher. «Water molecules form tetrahedral bonds that take up a lot of space. As water cools, it expands and decreases in density ».
Although, there were theories about the reversible structural changes to which the water is exposed before crystallizing under the same temperature range used in the experiment, there were no empirical reports in this regard.
“This temperature range is very difficult to achieve and control experimentally, and that is what the pulsed heating technique surpassed”said Kringle, who worked on the experiments and data analysis with another postdoctoral researcher, Wyatt Thornley.
In a super-cooled state, water in liquid form, by remaining below levels considerably below the normal freezing point, loses stability. This condition is called a metastable state, since its structure does not change, it only becomes unbalanced.
Through this research, the scientists use the intervention of their laser technology to measure the speed at which water crystallizes and diffuses.
A first advance, reported through the magazine Science In September 2020, he outlined the first data collected, making a comparison between the temperature ranges of the experiment and the levels of cold that can be perceived beyond the Earth’s atmosphere.
A second report, published in April by the magazine Proceedings of the National Academy of Sciences, provided an in-depth analysis of structural changes, beyond just focusing on qualitative research work.
Currently, the work continues, in search of deeper data that are still a mystery about water and its less traditional states.
By reporting the latest advances in this research, the PNNL highlighted the importance of knowing these new aspects of water, as they may imply an important impact on the understanding of climate change and some related biological and physical processes, in the optimized development of chemicals for energy and nuclear processing and even new drugs.
Banner photo: Loni Kringle, Pacific Northwest National Laboratory