SPECULATIVE SCIENCE



Why is water wet? Water isn't wet. Wetness is a description of our experience of water; what happens to us when we come into contact with water in such a way that it impinges on our state of being. We, or our possessions, 'get wet'. A less impinging sense experience of water is that it is cold or warm, while visual experience tells us that it is green or blue or muddy or fast-flowing. We learn by experience that a sensation of wetness is associated with water: 'there must be a leak/I must have sat in something.' Jacqueline Castles, London W2. Any fluid could be said to be wet if wetness is a result of the sensation caused by the movement of a fluid over the skin. Have you ever noticed that you can't feel wetness if you hold your hand perfectly stillwhile it is submerged, or that a drop of water on the skin doesn't feel wet? Chris and Shevvy Ould, Chesterfield, Derbyshire. The wetness of water is thought to be due to its high moisture content. (Dr) Jason A. Rush, Dept of Mathematics, Edinburgh University WATER is wet to make it a more marketable commodity. Sam McBride-Dick, Colchester. The questioner will be little enlightened by the previous replies and you must surely give him or her another chance. Twoanswers were humorous; two were just wet. As an amateur photographer, I am familiar with what is, I think properly, called wetting agent, which is added to water - to the final washing after developing and fixing - to make it wet with respect to the surfaces of photographic film. Without this agent the water resides on film in blobs, resulting in drying marks; with it, most of the water drains off and the rest dries evenly. So in response to the query I would say (a) water isn't always wet; wetness is always relative to a given substance and/or type of surface and (b) as to why it is wet when it is, presumably the answer is in terms of surface tension. Laurie Hollings, Brighton. Water is wet, in the sense of being a liquid which flows easily, because its viscosity is low, which is because its molecules are rather loosely joined together. The sensation of wetness is largely due to the cooling caused by evaporation, and water has a rather high latent heat of vaporisation, which is the amount of heat it removes from its surroundings in order to convert liquid water into water vapour. John Geake, Handforth, Cheshire. None of the answers given to this question so far quite gets to the chemical explanation for water's 'wetness.' Wetness is here synonymous with 'clingingness' - water wets because it clings. Water, of course, is molecularly H 2 O and this compound of hydrogen and oxygen is electrically neutral. However, there are also in water many free charged hydroxyls (-OH-, negatively charged) and hydrogen ions (H+ positively charged). These charged particles retain the ability to attract other charged particles (with the opposite charge) just as magnets do. In this way they stick or cling, involving other neutral H 2 O molecules at the same time. If water was made up entirely of neutral particles it would not cling, or wet, because the component elements would 'prefer' to stick to each other rather than to make bonds with other substances. Ian Flintoff, London SW6. Ian Flintoff has surely misrepresented the chemistry behind water's properties. Hydroxyl ions and hydrogen ions in water, far from being 'many' are very few (pure water contains some 556 million water molecules for every hydrogen ion). Water molecules are indeed 'electrically neutral' but are highly polar molecules, that is they have a positive 'end' and a negative 'end,' though neither 'end' carries a full unit of charge. It is this polarity which causes water molecules to 'stick to' one another and, given the chance, to other molecules of a polar nature. Other liquids can be wet, even those which contain molecules which are entirely non-polar (e.g. octane, benzine and even liquid nitrogen - don't try 'em!), but only in relation to another substance because wetness is to do with surface tension and that implies an interface between two substances. For this reason water is rather poor at wetting things: try washing your hands without soap! The molecules of water do prefer to stick to one another than to molecules of other substances but this effect is easily overcome by introducing another substance which interferes with the interactions between the water molecules. This allows the water molecules to interact with the molecules in the other surface instead. C. A. Mitchell, Reading, Berks HARRODS stock a line in "dry water" that is only minimally wet. However, before consumption it is necessary to dilute it. Richard Harrold Suratthani, Thailand (mathus@samart.co.th) Back in the old days, when water was where we needed to spend our time, touch was a lot more important than it is now. We as beings had to be immediately aware if we were going in or out of water. Therefore, the feeling of wet is a primal sensory reminder.



However, thereafter once we ascended onto the land and trees, the feeling of wet became a sensory reminder of something out of the ordinary; it is raining - get shelter, you fell in a creek - start swimming.



The reason it feels as it feels when water touches the skin is actually a complex electro-chemical reaction which works at amazing speeds. The sensory inputs are a combination of:



1. Your body's pH at that moment

2. The water's pH

3. Your body's temperature at that moment

4. The water's temperature

5. The atmospheric pressure

6. Molecular polarity

Ewan Sweeney, Swindon, UK New scientific information suggests that water doesn't behave as a liquid until after there are more than six molecules. For everyday purposes, there is much more than that, so until the exact relationship of the water to itself and to other substances can be proven by scientific means, then either answer to the question, why is water wet, whether it is or is not, is entirely philisophical and as long as there is evidence to support either theory, or rather no evidence to disprove either of them, then either answer is correct based on your own individual opinion and evaluation of the evidence that is at this time present in the scientific community. So, by the definition of wet, which is the condition of being covered or soaked in liquid, then water isn't wet, it just makes other things wet. W.C. Dutton, Staffordsville, USA Water is wet because when you have water on your clothes or skin it evaporates into the surrounding air. Evaporation produces cooling because it's like energy. Holly and Chloe, Bapchild, England Just look at the definition of what "Wet" is- I used websters- wet = "consisting of, containing, covered with, or soaked with liquid" By definition water is wet because it consists of and contains liquid. Angelo F, New York, USA It is interesting to look at the word itself 'Etymology: Middle English, partly from past participle of weten to wet & partly from Old English wet; akin to Old Norse wet, Old English wæter water'(Merriam-Webster Dictionary) Ellen Rodda, Wellington, New Zealand Water is wet because it is a viscous liquid with a fairly low surface tension Peter Twot, Leeds The wetness of water is just physical sensation...action potentials relaying the information up the CNS are interpreted as 'wet' because that was what you were taught growing up. Steve West, Los Angeles, California USA Water isn't wet because it is a liquid that wets things. Once you come into contact with water you become wet. Until then water is liquid and you are dry. Abdul Basir, Philadelphia, US water is wet because it is sticky. It sticks to your skin but it is only sticky enough to hold a bit at most a drop of water and it goes slihtly in your skin and will eventually get soaked. connor, diggle england I love it. Such a simple question and yet such a range of answers. Particular thanks to Dr Jason Rush from Edinburgh University who gave me a delightful laugh Walter van Straaten, Tenbury Wells, United Kingdom Water is wet because we perceive it to be, it cannot be just due to learning and experience or else it would be different for everyone. When two sensations are combined, that of light touch and coolness, we perceive wet. This has been studied since the 1800's and this illusion (thurnbergs illusion)of wetness has been replicated with cold metal disks. When you place a cool metal disk on somones forehead they often perceieve it as water, perhaps even expecting it to drip. This is the perception of wetness according to humans. Dr John Martin, Peoria U.S. Because cohesive forces are stronger than adhesive forces. Regent Kwena Moloto, Gauteng, South Africa All correct answers to the question why, "water is wet" simply put, because it is an adjective of the word. (Commercial Saturation diver.) john Elstob, United Kingdom All the above answers are solid on the liquidity or wetness of water - so to speak. But I will add that, water is 'wet', because that is what we call it. That is to say the sound we utter when attempting to describe a quality of water. Teddy Mcd, Vanc. Canada The water is WET because it is a liquid and all liquid is wet. Prince Dave, Roxas, Philippines Water is not wet it is just what are we feeling. Devdatt Khaire , Guajrat India Water is not wet. Wetness is a description of our experience of water what happens to us when we came into contact with water in such a way that it impinges on our states of being we, or our possesions get wet. Yasir mushtaq bhat (kwn), Kanelwon bijbehara j&k India Is there such thing a dry water? Nancy, Luanda Angola



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