Analysis: Water makes up three-quarters of the earth's surface and 60 percent of our bodies so it's vital to our well-being

By Sylvia Draper, TCD

What is water?

Water is a very unique substance because it is the only chemical that exists at room temperature in all three states, namely gas, liquid and solid. It expands on heating, as its molecules vibrate more quickly and move apart, and contracts on cooling, except between four and zero degrees Celsius when it expands again to form ice. This expansion in its solid form allows ice to float on water. Life would be very different if ice dropped like a stone on freezing like most materials. - there would have been no Titanic disaster for a start!

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From RTÉ News, a 2016 report on Belfast’s Titanic Visitors’ Centre welcoming its three-millionth guest

Its chemical formula H2O simply means that there is one central oxygen atom attached to two H atoms in every molecule of water which makes it V-shaped. Each oxygen atom is slightly electron-rich and each hydrogen atom electron-poor so water molecules are attracted to each other. They shake hands with each other, each one holding the congregation of water molecules together. So efficient is this hydrogen bonding that water can rise up a narrow tube such as a tree root and has a surface tension that allows insects to "walk on water".  It also means that you need 100oC of heat at 1 atmosphere to make water molecules break away from each other. This is where our centigrade temperature scale comes from.

Where did all this water come from?

Water came to be in the universe as a by-product from the formation of stars. When stars are born, huge amounts of gas (including abundant ones like H2 and O2) and other material are thrown outward, creating shockwaves that compress and heat the gases. On July 22nd 2011, a quasar 12 billion light years from Earth was found to be surrounded by a huge water cloud containing 140 trillion times more water than is found on earth. Other planets have atmospheres containing water - Mars is 3.4 percent water and one of Saturn’s moons is 91 percent water - and much of it is ice.

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From RTÉ News, a report on researchers finding evidence of a lake on Mars

Earth is called the Blue Planet because 71 percent of its surface is covered in water. Much of the water on earth is held in oceans or deep underground – in fact, only one percent is fit for drinking. This and the fact that the human demand for water has risen seven-fold over the last 100 years means that 40 percent of the Earth’s population suffer serious water shortages.

How Important is it?

Water is the giver of life and every living organism relies on water. Water is known as the Universal Solvent – because it dissolves so many other substances. In the body this means that provides a nutrient transport system and an information waterway for vital messaging and metabolic processes.  These all involve water, either to create bigger molecules like starches, triglycerides and proteins or to break-up big molecules to make smaller ones like amino acids, glucose or fatty acids. Cells have water inside and out and the process of water passing through a cell membrane (osmosis) even provides the body with the energy to manufacture special chemicals.

Does my body need an adequate supply of water at all times?

Given that 60 percent of an adult body (75 percent of a child) is made of water, the progressive dehydration that can occur on ageing causes major health problems. The body has a very strict drought mechanism that is dominated by histamine generation which indirectly reduces our response to a sensation of thirst. So, whether thirsty or not, each of us should be drinking 1.5 litres or more of water a day (eight glasses).  Sports drinks are not more hydrating than water but, being more palatable, they encourage you to take in more fluid. The bland taste of water means that most people stop drinking before they are fully hydrated.

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From RTÉ 2fm's Game On, Damien O'Meara discusses the problem of hydration for boxers with Barry J White 

What kind of water should I be drinking?

Because water dissolves so many substances, it is difficult to obtain pure. Pure water has all its dissolved matter removed. This includes nasty chemicals like arsenic (from pesticides and herbicides), chlorine (from sanitizing to kill bacteria and other living organisms), phthalates (used to make plastic bottles), organic trihalomethanes (from industrial processes) and nitrates (from fertilizers). It also means good chemicals (like Magnesium and Calcium which are absorbed by water passing through limestone).

Ideally, drinking water should contain a high portion of "good minerals" (i.e. toward 100 mg/L) and as small a proportion of the bad ones as possible (i.e. 0 to <10 mg/L). The presence of the bad ones is routinely checked in municipal water supplies.

What about bottled water?

Bottled water companies are obliged to list all their constituent ions on the label. There are websites that compare these for all manufacturers. Water "bottled at source" is what you want. This is natural water and usually means a high Mg, Ca and bicarbonate content in Ireland. These are good minerals indicating that the water is probably hard water and slightly alkali.

Keep bottled water out of sunlight to slow down the entry of plasticides into the water and pick good sell-by-dates so as to drink it as soon after bottling as possible.

"Water "bottled at source" is what you want"

What is softened water ?

Hard water leaves a residue after boiling which cakes heating elements and impairs the operation of kitchen appliances like dishwashers. Several processes are used to soften water and remove these ions such as adding Ca(OH)2, or using ion-exchange columns which swap the Ca or Mg for Na. This is good for the appliances, but not necessarily for drinking. Washing in softened water needs less soap but often more water as it is less effective at washing the soap away.

What about tap water?

Many homes use water purifiers which are activated charcoal filters. They do not remove Mg/Ca or nitrates, but are effective at removing much of the chlorine (and fluorine added to strengthen teeth enamel), organics (trihalomethanes), odours and colours. You must replace the filters regularly because the impurities stick to them and reduce their efficiency. Over-use allows moulds or bacteria to build-up on the filter surface.

Boiled water will have no living micro-organisms but always re-fill the kettle with fresh water so that you are not concentrating the mineral content (and higher boiling organic material in the water) time after time.

READ: Why has a wet island run out of water?

A more expensive purification technique is reverse osmosis. This involves pushing the water through a microporous membrane where the pores are so small that molecules larger than water get stuck. The water is pushed through under pressure. The downside is that for every gallon of water purified, two gallons are wasted and this waste water is now richer in contaminants.

Can you survive without water?

For a maximum of about 10 days. In a hot climate and in the absence of any alternatives, you can reclaim water from urine. You need two plastic bottles sealed together at the top. Putting urine in one, you carefully turn the bottles horizontal and bury the empty one in the ground. The exposed bottle gets hot from sunlight, causing the water to evaporate and condense into the empty bottle. This leaves the toxins behind, but you might find detaching the bottles without contaminating your evaporated water a bit tricky.

Professor Sylvia Draper is Professor in Inorganic Chemistry at the School of Chemistry at TCD. She a former Irish Research Council awardee.


The views expressed here are those of the author and do not represent or reflect the views of RTÉ