Abu Dhabi, UAESunday 25 August 2019

New study looks into the everyday miracle that is water

While most compounds shrink when they freeze, this stuff expands. It’s very hard to be heated up, but once turned into liquid, it’s peculiarly sticky and extremely resistant to pressure.
A man braves the water collecting on the ground during a rainstorm in Abu Dhabi. Delores Johnson / The National
A man braves the water collecting on the ground during a rainstorm in Abu Dhabi. Delores Johnson / The National

Whatever the truth about claims that cloud-seeding was responsible for the floods in March, one thing is certain – during the downpours, thousands of people in the UAE were exposed to a bizarre quantum substance at the focus of ­intense scientific research.

Colourless and odourless, its behaviour is unlike that of any other known compound. While most shrink when they freeze, this stuff expands. It’s very hard to be heated up but once turned into liquid, it’s extremely resistant to pressure.

Exposure to it in any form can be fatal. Its liquid form is responsible for dozens of deaths each year in the UAE.

Scientists sometimes call it ­dihydrogen oxide after its chemical formula by which, paradoxically, it is far better known – H2O, or water.

The ubiquity of water on the Earth masks its sheer weirdness as a chemical. The very fact that it is naturally present in three states of matter – solid, liquid and gas, in ice, water and steam respectively – makes it unique.

Now, a flurry of discoveries are casting light on the source of the strange behaviour of water and its profound connection to the very processes of life.

Everyone knows the importance of water to survival.

While we can go without food for weeks, just a few days without water can be fatal.

Water is peculiarly difficult to heat, having a specific heat ­capacity 10 times higher even than solid iron.

Yet while this adds to the cost of waiting for the kettle to boil, it ­allows the Earth’s oceans to act as colossal heat sinks, smoothing out the temperature swings during the seasons.

It has also helped to buy us time to deal with the impact of global warming.

The fact that solid water is less dense than its liquid form prevented the world’s oceans from freezing solid aeons ago.

If water were like most substances, it would shrink as it froze, becoming denser and sinking to the sea bed. It would then build up and turn the oceans solid, leading to the death of all marine life.

Luckily, the buoyancy of ice also means that it traps an insulating layer of air beneath it that allows marine life to survive in winter.

Or rather, not luckily at all. At the last count, water has been found to have no fewer than 60 anomalous properties.

Now, theoretical and experimental work has revealed that they are the consequence of cosmic laws written into the very ­design of the universe.

Specifically, they are the result of quantum phenomena – the strange rules that govern the sub-atomic world.

These manifest themselves in the behaviour of that famous molecule H2O: a V-shaped ­arrangement of two hydrogen ­atoms with an oxygen atom sitting between them.

The three atoms are held together by chemical bonds and it is these that follow the dictates of quantum theory.

But it is not just the bonds within each water molecule that ­affect its behaviour. The way each molecule bonds to its neighbours is crucial.

These so-called hydrogen bonds are strong enough to ­allow water molecules to link up – and also weak enough to be easily broken.

As a result, every glass of water is a seething morass of molecules, constantly forming and breaking connections with each other.

Understanding that chemical dance is now the focus of a global scientific effort.

And one arrangement of dancers, in particular, is attracting attention: a cluster of six water molecules called the water hexamer.

First identified in the mid-1990s, it is the simplest three-­dimensional arrangement of water molecules. As such, it’s the basic building-block of any mass of water – from a raindrop to an ocean.

Water hexamers come in a range of shapes resembling prisms, cages and open books, each with different properties.

Now, scientists are finding that water exploits strange quantum effects that allow it to switch shapes in seemingly impossible ways.

An international team led by Jeremy Richardson at the University of Cambridge in the UK has just reported new evidence that water hexamers can change shape even when there is no ­energy to help.

At normal temperatures, the hexamers in a glass of water are constantly forming and breaking up, the energy needed to do so coming from their surroundings.

But Dr Richardson and his colleagues have shown that the process can continue even in ice.

To do it, the molecules exploit the fact that, according to quantum theory, there is always a fleeting level of uncertainty about the energy of atoms. Water hexamers exploit this to take on new shapes in the absence of any conventional source of energy.

According to Dr Richardson and his colleagues, the quantum energy is used specifically to break two bonds in the hexamer, producing new shapes.

Even individual water molecules exploit this “energy from nowhere” when joining up with their neighbours.

The hydrogen atom on each leg of the V-shaped molecules bonds to the oxygen atom of its neighbour.

But it is not a rigid bond. The hydrogen and oxygen atom yo-yo in and out, propelled by quantum energy. At the same time, the two molecules flex up and down, again driven by that energy from nowhere.

According to an international team led by Dr Michele Ceriotti of the Ecole Polytechnique of Lausanne, Switzerland, these two effects become stronger or weaker according to how densely packed the molecules are, and it is their relative strength that plays a key role in water’s weird, life-sustaining properties.

Last month, researchers at the Oak Ridge National Laboratory in Tennessee reported yet another manifestation of quantum ­behaviour, this time when water is crammed into molecular-sized channels just a few ­atoms across.

This time the molecules exploit quantum uncertainty to tunnel through the channels in ways that are simply impossible according to the everyday laws of physics.

It’s a discovery that has sparked excitement among biochemists, who believe it casts light on how water interacts with the complex structures of proteins – the key chemicals that sustain life itself.

The formation and action of proteins has long been known to depend on the presence of water molecules.

Now, it seems the strange quantum tunnelling abilities of H2O may hold the key.

Scientists have yet to work out the full implications of these new discoveries.

But one thing is already clear: when we drink water, we’re topping up with a life-giving liquid packed with quantum magic.

Robert Matthews is Visiting Professor of Science at Aston University, Birmingham. His new book Chancing It: The Laws of Chance and How They can Work for You is out now.

Updated: May 7, 2016 04:00 AM

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