By Tim Philp For The Expositor
Thursday, December 29, 2016 6:48:28 EST PM
A few months ago, I wrote about one of the most remarkable substances on our planet - dihydrogen monoxide, commonly known as water.
This substance is vital for life as we know it and it covers more than 70 per cent of our planet. Indeed, we are composed of about 60 per cent water. It is in the air that we breathe and the foods we eat. And it is a tremendous driver for our climate.
Water has many interesting properties, but we are still learning about this remarkable substance.
In its solid form, it can assume many different molecular arrangements. The molecules can form crystals in cubic, tetragonal, monodinic, rhombohedral and even non-crystalline forms, depending on pressures and how the ice was formed. It can be clear, blue, white and other colours depending on impurities lodged within it.
Ice can have different kinds of molecular symmetry and can even have dramatically different densities. There are 17 known crystalline forms of ice and ice can form at different temperatures depending upon pressure and impurities present in the water.
In gaseous form, water can be transparent to light, or it can bend light in interesting ways. As tiny water droplets, it can form clouds in the sky or fog on the ground. It can bend light into colourful rainbows and create halos known as moonbows or even sun dogs. Water is called the universal solvent because it is capable of dissolving many chemicals into solution and it is the entire basis for the chemical processes that keep us alive.
Because of the importance of water to our climate, our ecology and life itself, you would think that we would know all there is to know about this remarkable substance. That is a long way from the truth.
While there are many different forms of ice, it was always assumed that there was only one form of water. Now, it seems this might not be true. Recently, a team of scientists has reported that water appears to change some of its properties as its temperature increases.
The team measured properties, such as: thermal conductivity -- how well it conducts heat; refractive index -- how well it bends light; conductivity -- how well it conducts electricity; and the dielectric constant -- how well an electric field can propagate through the water. In each instance, the scientists noted that these properties changed when certain critical temperatures were reached.
For instance, between 40C and 65C, the value of each of these properties appeared to shift. At 50C, the refractive index changes, at 53C electrical conductivity changes, at 57C the surface tension changes and at 64C thermal conductivity shifts.
These changes were unsuspected by scientists. It is remarkable that, after all this time, we are still discovering new properties of such a common substance.
It is such a simple substance, too. Water comprises only three atoms - one oxygen atom linked with two hydrogen atoms. Atoms are the smallest building blocks of matter that have distinct chemical properties. You cannot split an atom of oxygen and still have oxygen. You can split them, but you will have other substances in their place.
The oxygen atom is linked with two hydrogen atoms by sharing electrons. This ionic bonding is strong, but they can be broken apart by applying energy such as electricity to the water and you will get hydrogen gas and oxygen gas. Water molecules also form weak bonds with other water molecules. These bonds break and reform easily and this allows water in its liquid state to flow. It is also responsible for the surface tension of water that water striders use to walk over the surface of ponds.
The new discovery still needs to be confirmed by other scientists working to replicate these results, but, if confirmed, it presents a lot of interesting questions for biologists, in particular. Does the change in properties of water have any implications for how water is used by life? There are many organisms that thrive in temperatures where these phase transitions of water occur. Do these transitions help these organisms survive in such heat, or are there other reasons for their remarkable resistance to temperature.
I find it fascinating that such a simple and abundant substance can still surprise us. It is one reason that science can never grow stale - there is always something new to learn.
Tim Philp has enjoyed science since he was old enough to read. Having worked in technical fields all his life, he shares his love of science with readers weekly. He can be reached by e-mail at: firstname.lastname@example.org or via snail mail c/o The Expositor.
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