DR. S.M. ALAM & DR. M.A. KHAN
Feb 14 - 20, 2011
Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often coexists on earth with its solid state, ice and gaseous state, water vapor or steam.
On earth, it is found mostly in oceans and other large water bodies, with 1.6 per cent of water below ground in aquifers and 0.001 per cent in the air as vapor, clouds (formed of solid and liquid water particles suspended in air) and precipitation. Oceans hold 97 per cent of surface water, glaciers and polar ice caps 2.4 per cent and other land surface water such as rivers, lakes, and ponds 0.6 per cent. A very small amount of the earth's water is contained within biological bodies and manufactured products. Water on earth moves continually through a cycle of evaporation or transpiration (evapo-transpiration), precipitation and runoff, usually reaching the sea.
The Holy Quran has described many facts about water. The Surah Al-Anbiya21, Verse-30 states that: And We (Allah) have made from water every living thing. Surah An-Nur-24, Verse-45, states: Allah had created every moving (living) creature from water. Of them, there are some that creep on their bellies and some that walk on two legs and some that walk on four.
Allah creates what He wills. Verily, Allah is able to do all things. In Surah Al-Furqan-25, Verses 48-50, it is stated that: And We (Allah) send down pure water from the sky. That We may give life thereby to a dead land and We give to drink thereof many of the cattle and men that We had created. And indeed We have distributed it (rain or water) amongst them in order that they may remember (the Grace of Allah) but most men (refuse to accept the Truth and Faith) and accept nothing but disbelief or ingratitude.
Again, in Surah Al-Furqan-25, Verse-54, it is stated. And it is He Who created man from water. Yet, In the same Surah (Al-Furqan) at Verse-53 , it is stated that: And it is He Who has let free the two seas (kinds of water) this is palatable and sweet and that is salt and bitter and He has set a barrier and a complete partition between them. In Surah Ar-Rahman-55, Verse-19/20, it is stated that: He (Allah) has let loose the two seas (the salt and fresh water) meeting together.
All these facts state that water is boon for all living beings. There are many other Surahs which have revealed the salient features of water (river, seas, rain etc.)
The pure and clean drinking water is essential to humans and other life forms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world. There is a clear correlation between access to safe water and GDP per capita. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A recent report (November 2009) suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50 per cent. Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation.
Water appears in nature in all three common states of matter and may take many different forms on earth: water vapor and clouds in the sky; seawater and icebergs in the polar oceans; glaciers and rivers in the mountains; and the liquid in aquifers in the ground.
Water is a liquid at standard temperature and pressure. It is tasteless and odorless. The intrinsic color of water and ice is a very slight blue hue, although both appear colorless in small quantities. Water vapor is essentially invisible as a gas. Water is transparent in the visible electromagnetic spectrum. Thus, aquatic plants can live in water because sunlight can reach them. Ultra-violet and infrared light is strongly absorbed. Water is a good solvent and is often referred to as the universal solvent. Substances that dissolve in water, e.g. salts, sugars, acids, alkalis, and some gases - especially oxygen, carbon dioxide (carbonation) are known as hydrophilic (water-loving) substances, while those that do not mix well with water (e.g., fats and oils), are known as hydrophobic (water-fearing) substances.
All the major components in cells (proteins, DNA, and polysaccharides) are also dissolved in water. Pure water has a low electrical conductivity, but this increases significantly with the dissolution of a small amount of ionic material such as sodium chloride. The boiling point of water (and all other liquids) is dependent on the barometric pressure. For example, on the top of Mt. Everest water boils at 68†∞C (154†∞F), compared to 100†∞C (212†∞F) at sea level. Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid. The maximum density of water occurs at 3.98†∞C (39.16†∞F). It has the anomalous property of becoming less dense, not more, when it is cooled down to its solid form, ice. It expands to occupy 9 per cent greater volume in this solid state, which accounts for the fact of ice floating on liquid water. Water is miscible with many liquids, such as ethanol, in all proportions, forming a single homogeneous liquid. On the other hand, water and most oils are immiscible usually forming layers according to increasing density from the top.
As a gas, water vapor is completely miscible with air. Water can be split by electrolysis into hydrogen and oxygen. As an oxide of hydrogen, water is formed when hydrogen or hydrogen-containing compounds burn or react with oxygen or oxygen-containing compounds. Water is not a fuel. It is an end-product of the combustion of hydrogen. The energy required to split water into hydrogen and oxygen by electrolysis or any other means is greater than the energy that can be collected when the hydrogen and oxygen recombine.
From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body.
Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Without water, these particular metabolic processes could not exist.
Water is fundamental to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO2 (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO2 in the process (cellular respiration).
Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H+, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH?) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7.
The most important use of water in agriculture is for irrigation, which is a key component to produce enough food. Irrigation takes up to 90 per cent of water withdrawn in some developing countries and significant proportions in more economically developed countries.
The human body contains anywhere from 55 per cent to 78 per cent water depending on body size. To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people, though most advocates agree that 6ñ7 glasses of water (approximately 2 liters) daily is the minimum to maintain proper hydration. Medical literature favors a lower consumption, typically 1 liter of water for an average male, excluding extra requirements due to fluid loss from exercise or warm weather.
For those who have healthy kidneys, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) it is dangerous to drink too little. People can drink far more water than necessary while exercising. The popular claim that "a person should consume eight glasses of water per day" seems to have no real basis in science. Similar misconceptions concerning the effect of water on weight loss and constipation have also been dispelled.
Humans require water that does not contain too many impurities. Common impurities include metal salts and oxides (including copper, iron, calcium, and lead) and/or harmful bacteria, such as Vibrio. The propensity of water to form solutions and emulsions is useful in various washing processes. Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using water to dissolve and extract substances.
Washing is also an important component of several aspects of personal body hygiene. Water is widely used in chemical reactions as a solvent or reactant and less commonly as a solute or catalyst. In inorganic reactions, water is a common solvent, dissolving many ionic compounds. Water and steam are used as heat transfer fluids in diverse heat exchange systems, due to its availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization. A disadvantage is that water and steam are somewhat corrosive. In almost all electric power stations, water is the coolant, which vaporizes and drives steam turbines to drive generators.
In the U.S., cooling power plants is the largest use of water. In the nuclear power industry, water can also be used as a neutron moderator. In most nuclear reactors, water is both a coolant and a moderator. This provides something of a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down ñ however other methods are favored for stopping a reaction and it is preferred to keep the nuclear core covered with water so as to ensure adequate cooling. Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. However, only distilled water can be used to fight fires of electric equipment, because impure water is electrically conductive. Water is not suitable for use on fires of oils and organic solvents, because they float on water and the explosive boiling of water tends to spread the burning liquid.
Use of water in fire fighting should also take into account the hazards of a steam explosion, which may occur when water is used on very hot fires in confined spaces, and of a hydrogen explosion, when substances which react with water, such as certain metals or hot graphite, decompose the water, producing hydrogen gas. A steam explosion occurrs when the extreme over-heating of the core causes water to flash into steam. A hydrogen explosion may occur as a result of reaction between steam and hot zirconium.
Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, waterskiing, boating, surfing, and diving. In addition, some sports, like ice hockey and ice skating, are played on ice. Lakesides, beaches, and water parks are popular places for people to go to relax and enjoy recreation. Many find the sound and appearance of flowing water to be calming, and fountains and other water features are popular decorations. Some keep fish and other life in aquariums or ponds for show, fun, and companionship. Humans also use water for snow sports i.e. skiing, sledding, snowmobiling, or snowboarding, which requires the water to be frozen. People may also use water for play fighting such as with snowballs, water guns, or water balloons
The water industry provides drinking water and wastewater services (including sewage treatment) to households and industry. Water supply facilities include water wells cisterns for rainwater harvesting, water supply network, water purification facilities, water tanks, water towers, water pipes including old aqueducts. Atmospheric water generators are in development.
Drinking water is often collected at springs, extracted from artificial borings (wells) in the ground, or pumped from lakes and rivers. Building more wells in adequate places is thus a possible way to produce more water, assuming the aquifers can supply an adequate flow. Water may require purification for human consumption. This may involve removal of un-dissolved substances, dissolved substances, and harmful microbes. Popular methods are filtering with sand, which only removes un-dissolved material, while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant seawater is a more expensive solution used in coastal arid climates. The distribution of drinking water is done through municipal water systems, tanker delivery or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource and to finance the boring of wells or the construction of dams and reservoirs.
Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the polluter. Like other types of pollution, this does not enter standard accounting of market costs, being conceived as externalities for which the market cannot account. Thus, other people pay the price of water pollution, while the private firms' profits are not redistributed to the local population victim of this pollution. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bio-accumulate and if they are not biodegradable.
Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products. Solutes such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water are affected by solutes, as well as air pressure, which is in turn affected by altitude. Water boils at lower temperatures with the lower air pressure, which occurs at higher elevations. One mole of sucrose (sugar) per kilogram of water raises the boiling point of water by 0.51 ∞C, and one mole of salt per kg raises the boiling point by 1.02 ∞C; similarly, increasing the number of dissolved particles lowers water's freezing point. Solutes in water also affect water activity, which affects many chemical reactions and the growth of microbes in food.
Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water. Solutes in water lower water activity. This is important to know because most bacterial growth ceases at low levels of water activity.
Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon.
Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains. The hardness of water may be altered or treated by using a chemical ion exchange system. The hardness of water also affects its pH balance which plays a critical role in food processing. For example, hard water prevents successful production of clear beverages.
Water is a wonderful gift from the Al-Mighty Allah to all creatures living on earth, beneath the earth and present in the atmosphere.