IRISH PEOPLE are often said to be obsessed by the weather. This is hardly surprising given the variety on offer across such a small expanse of land and sea. Recently however, the primary focus of the populace has been on water. Over the festive period some had none for lengthy periods of time, while others experienced burst pipes, leaks and flooding. Some were beset by both sets of circumstances, writes PAUL O'DONOGHUE
Following recovery from the woes it can bring, it is worth considering this fascinating substance in more detail and the extensive influence it exerts on all our lives. Matter generally occurs in three states: solid, liquid and gaseous. Water is extremely unusual in that it can manifest all three phases at the same time under ambient conditions.
Think for example, of standing on a canal bridge during the recent cold snap watching the water flow (liquid), with ice (solid) underfoot while clouds (gaseous) drift overhead.
Water makes up between 60 and 80 per cent of our body mass and covers more than 75 per cent of the Earth’s surface. It has unusually high boiling and melting points, is an excellent solvent and most spectacularly, its solid form ice, floats on its liquid form.
The solid form of almost all materials has a greater density than the liquid form and will sink. Water exhibits maximum density at four degrees centigrade and as a consequence rivers and seas freeze from the top down as the relatively warmer water drifts downwards. If this were not the case, aquatic life as we know it would not exist.
When water freezes it increases in volume by about 9 per cent. If confined during this transition it exerts tremendous force, hence the burst pipes many have endured. Freezing water also fractures rock and contributes to the formation of potholes, another popular Irish obsession.
Water is crucial to life, with all known biochemical processes occurring in an aqueous environment. Photosynthesis for example, supplies the primary nutrients for all life forms and is the primary source of atmospheric oxygen. During this process carbon dioxide is combined with water, and utilising energy from sunlight, carbohydrates and oxygen are produced.
Many of the unique properties of water are due to the nature of its molecular structure. Water is made up of two atoms of hydrogen combined with one atom of oxygen. This formula, H2O, is well known to most people. However, what is perhaps less familiar is the phenomenon of hydrogen-bonding which also occurs in water. The molecule of water is not linear, but has an extended V shape, with an angle at the apex of 104.5 degrees.
The oxygen end of the molecule is electronegative, while the hydrogen ends are electropositive. This results in a structure which behaves rather like a magnet and as a consequence, the hydrogen ends of the molecule are drawn towards the oxygen end to form what are known as hydrogen bonds. These allow the individual molecules to bond together quite tightly with their neighbours, accounting for the relatively high boiling and freezing points of water. Without hydrogen-bonding, water would boil at about minus 90 degrees centigrade and would exist on Earth as a gas with all that that implies.
Water also has a high surface tension due to lateral attraction between molecules on the water surface. This is why some insects can walk on water.
It is interesting to consider how much water is processed in the body. The kidneys process about 180 litres per day, most of which is returned to the blood stream. Lymph flow utilises 1 to 2.5 litres per day, while bowel function utilises 8 to 9 litres per day. The bulk of this water is exchanged within the body, not actually lost. The most staggering figure in this regard is the 80,000 litres per day that traverse the capillary walls.
Daily water loss from the body is accounted for via breathing (800ml), sweating (100ml) and excretion (1.1 litres). It is this two litres that must be replaced through water intake. These figures are approximations and will vary depending on a range of factors including humidity, exercise regime, age and health status.
However, this does not mean that you must drink two litres of water per day. About 20 per cent of our water requirement is obtained from solid food while tea, coffee, juice, milk and other beverages are also largely composed of water. The diuretic properties of tea and coffee are not very significant in this regard and studies have indicated that most of the water content is retained from these drinks.
For fun, or to amuse and inform children, you might like to demonstrate some of the properties of water alluded to above. To demonstrate the electrostatic forces surrounding the water molecule, run a thin flow from the kitchen tap. Obtain a biro and rub it vigorously with a woollen scarf or jumper. Hold the biro close to the stream of water and it will be drawn towards the pen.
To demonstrate the surface tension of water, try floating a paper clip. After this fails (as the clip must be placed gently and flat), obtain a small piece of tissue and place it flat on the surface of a glass of water. Place the paper clip on the tissue. After a little time the paper will sink and the clip will float. (You may need to assist the sinking of the tissue with a little prodding from a knife point.)
Paul O’Donoghue is a clinical psychologist and founder member of the Irish Skeptics Society. contact @irishskeptics.org.