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Miraculous Water

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Published Date Written by Ferdinand Van Niekerk

Water is baffling – even to scientists. From its refusal to obey the ordinary rules of liquids to its insistence on becoming lighter when it freezes, water is as curious as it is vital.

H2O, two hydrogen atoms covalently bonded to a single oxygen atom, is the chemical composition of this fascinating substance. What makes it so fascinating? Let’s look at a few facts:

Say you put two pails of water outside on a freezing day. One contains hot water  (95ºC) and the other an equal amount of warm water (50ºC). Which freezes first?

The hot water freezes first! Why? One of several explanations is evaporation. If two equal masses of water are taken at very different starting temperatures, the evaporation rate of the hotter sample may reduce its mass sufficiently thereby compensating for the larger temperature drop needed to reach the freezing point. Water may lose up to 16% of its mass in cooling from 100 → 0ºC. The cooling effect of evaporation is twofold. First, the temperature drops due to heat loss in the phase change from water to vapour (latent heat of evaporation). Simultaneously, the vapour is carried off leaving less mass to be cooled.  Sounds mysterious, but this is science fact, not fiction!

Another interesting fact about water is that it can be super-cooled. Now what does this mean? Everybody knows that when you cool water to 0°C it forms ice ... except that in some cases it doesn't! You can actually chill very pure water past its freezing point (at standard pressure, no cheating!) without it ever becoming solid. It turns out that ice crystals need nucleation points to start forming. These nucleation points could be anything from gas bubbles to impurities to the rough surface of the container. Without these things, water would continue to be a ‘super-cooled’ liquid well below its freezing point. When nucleation is triggered, then super-cooled water would ‘instantly’ turn into ice, just like that!

How many phases of water are there? If you answer three (liquid, gas, and solid) you'd be wrong. There are at least five different phases of liquid water and 14 different phases (that scientists have found so far) of ice. We just discussed super-cooling. Well, it turns out that no matter what you do, at -38°C even the purest super-cooled water spontaneously turns into ice (with a little audible ‘bang’ no less). But what happens if you continue to lower the temperature? Well, at -120°C something strange starts to happen: the water becomes ultra-viscous, or thick like molasses. And below -135°C, it becomes "glassy water," a solid with no definite crystal structure.

At a molecular level, water is even more extraordinary. In 1995, a neutron scattering experiment got a strange result: physicists found that when neutrons were aimed at water molecules, they found 25% fewer hydrogen protons than expected. Long story short, at the level of attoseconds (10-18 seconds) there is a weird quantum effect and the chemical formula for water isn't H2O. It's actually H1.5O!

Water is the only substance that occurs naturally in all three basic phases of matter – solid, liquid and vapor (gas).  Water dissolves more substances than any other liquid. Wherever it travels, water carries chemicals, minerals and nutrients with it. And this forms the starting point of analytical chemistry. Because water does not only contain H2O molecules, various analytical techniques exist to identify which impurities are contained in this fascinating liquid so vital for life on earth. Minerals, dissolved gases, organic material, living organisms, to name but a few, can be quantified down to extremely low levels using sophisticated analytical methodology. If you wonder what exactly is going on in your glass of water, send it to UIS-AS. We are more than capable and will give you an accurate breakdown.

One last thought to ponder - there are approximately 1 400 000 000 000 litres of water available on earth, if you drink the recommended 8 glasses per day it will take you almost 2 billion years to finish it!

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