Water

Facts About Water

Yes, of course the most obvious fact about water is that it is wet, at least in the liquid state. But, there are many more facts about water that make it a most fascinating substance, one that all life on and in the Earth depends on.

Water is everywhere, from huge oceans to invisible water molecules making up water vapor in the air. Of course, you can see and feel the physical properties of water, but there are also many chemical, electrical, and atomic-scale properties of water that affect all life and substances on Earth.

Water is the most abundant and important inorganic compound on earth. It makes up 60 to 89-percent of the volume of most living cells, and it possesses several properties that make it vital to life. Water has a high heat capacity. Water absorbs and releases large amounts of heat before changing appreciably in temperature. This property prevents sudden changes in temperature caused by external factors, such as sun or wind exposure, or by internal conditions that release heat rapidly, such as vigorous muscle activity. As part of blood system or the environment, water redistributes heat among adjacent structures ensuing the temperature remains homeostatic.

When water evaporates, or vaporizes, water changes from a liquid to a gas, water vapor. The transformation requires that large amounts of heat be absorbed to break hydrogen bonds that hold water molecules together. This property is beneficial because as water evaporates from an object or organism large amounts of heat are removed providing efficient cooling. This property is referred to as high heat of vaporization.

Water is the best solvent in nature. It is called the universal solvent. Biological molecules do not react chemically unless they are in solution, and virtually all chemical reactions that occur in the living cells depend on water’s solvent properties. Water molecules are referred to as being polar. They orient with their slightly negative ends toward the positive ends of the solutes. This characteristic is called polarity, and it explains the reason that ionic compounds and other small reactive molecules, such as acids and bases, dissociate in water, where their ions separating from each other and become evenly scattered in the water forming a true solution.

Water also forms layers of water molecules, called hydration layers, around large charged molecules such as protein, shielding them from the effects of other charged substances in the areas and preventing them from settling out of solution. Such protein water mixtures are biological colloids. Water is also the major transport medium because it is an excellent polar solvent. Nutrients, gases, and metabolic wastes are carried dissolved in water based fluids. Wastes are excreted form living organisms in watery fluids. Specialized molecules that lubricate organisms also use water as the dissolving medium.

Water is an important reactant in many chemical reactions. Nutrients are decomposed by adding a water molecule to each chemical bond that is broken. Decomposition reactions are more specifically referred to as hydrolysis reactions. When large carbohydrates or protein molecules are synthesized from smaller molecules, a water molecule is removed for every bond formed, a reaction that is called dehydration synthesis.

Water forms resilient cushions, cushioning around certain biological structures providing protection from physical trauma.

When inorganic salts such as sodium chloride (NaCl) are dissolved in water, they undergo ionization or dissociation. They break apart into ions. Substances labeled acids and bases demonstrate similar behavior.

According to the United States Geological Survey (USGS), 71% of the Earth’s surface is covered in water, and of that 97% are the oceans. The Earth’s water can be broken into two different categories: freshwater and salt water. Fresh water is simply water that is not salty and can be found in the planet’s surface water such as streams, lakes, and frozen as ice, but also underground in aquifers. Fresh water is stored on the surface as surface water or stored underground in aquifers as groundwater. Salt water can be found in the world’s oceans.

Figure 1.1 shows that our planet’s water sources are limited. Freshwater is much easier to use for potable (drinkable) applications because it requires more simple treatment. However, it represents only a small fraction of the Earth’s water portfolio. A large proportion of the freshwater is locked in glaciers and is not accessible. As a result, less than 1% of the water present on the planet is groundwater and surface water that can be more easily used as potable water source. Although desalination plants have become more prevalent, they are very costly and their overall environmental impacts are unknown.

Some of water’s physical properties:

• Weight: 62.416 pounds/cubic foot at 32°F; 1,000 kilograms/cubic meter
• Weight: 61.998 pounds/cubic foot at 100°F; 993 kilograms/cubic meter
• Weight: 8.33 pounds/gallon; 1 kilogram/liter
• Density: 1 gram/cubic centimeter (cc) at 39.2°F, 0.95865 gram/cc at 212°F

Some water volume comparisons:

• 1 gallon = 4 quarts = 8 pints = 128 fluid ounces = 3.7854 liters
• 1 liter = 0.2642 gallons = 1.0568 quart
• 1 million gallons = 3.069 acre-feet = 133,685.64 cubic feet

Flow rates:

• 1 cubic foot/second (cfs) = 449 gallons/minute = 0.646 million gallons/day = 1.98 acre-feet/day

Water Facts

Water is called the “universal solvent”.

Why is water the “universal solvent”? Water is capable of dissolving a variety of different substances, which is why it is such a good solvent. And, water is called the “universal solvent” because it dissolves more substances than any other liquid. This is important to every living thing on earth. It means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

It is water’s chemical composition and physical attributes that make it such an excellent solvent. Water molecules have a polar arrangement of the oxygen and hydrogen atoms—one side (hydrogen) has a positive electrical charge and the other side (oxygen) had a negative charge. This allows the water molecule to become attracted to many other different types of molecules. Water can become so heavily attracted to a different molecule, like salt (NaCl), that it can disrupt the attractive forces that hold the sodium and chloride in the salt molecule together and, thus, dissolve it.

Pure water has a neutral pH of 7.

Which is neither acidic (less than 7) nor basic (greater than 7).

pH is a measure of how acidic/basic water is. The range goes from 0 to 14, with 7 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base. pH is reported in “logarithmic units”. Each number represents a 10-fold change in the acidity/basicness of the water. Water with a pH of five is ten times more acidic than water having a pH of six.

The pH of water is a very important measurement concerning water quality. A changing pH can be an indicator of increasing pollution or some other environmental factor.

Other Undesirable Effects:

1. When the pH increases, the disinfection activity of chlorine falls significantly.
2. High pH may cause increased halogen reactions, which produce chloroform and other THMs during chlorination.
3. Both excessively high and low pHs may cause increased corrosivity, which can, in turn, create taste problems, staining problems, and significant health hazards.
4. Metallic piping in contact with low-pH water will impart a metallic taste.
5. If the piping is iron or copper, high pH will cause oxide and carbonate compounds to be deposited, leaving red or green stains on fixtures and laundry.
6. At a high pH, drinking water acquires a bitter taste.
7. The high degree of mineralization often associated with basic waters results in encrustation of water pipes and water-using appliances.

A wide range of pH values in drinking water can be tolerated by consumers.

Normal rainfall has a pH of about 5.6—slightly acidic due to carbon dioxide gas from the atmosphere. You can see that acid rain can be very acidic, and it can affect the environment in a negative way. The pH of precipitation, and water bodies, vary widely across the United States. Natural and human processes determine the pH of water.

By the way…..for a solution to have a pH, it has to be aqueous (contains water). Thus, you can’t have a pH of vegetable oil or alcohol.

The most acidic waters ever measured are percolating through an underground mine at Iron Mountain, near the northern California town of Redding. Hot acid solutions, more concentrated than battery acid, are dripping from colorful mineral stalactites in the abandoned copper and zinc mine at Iron Mountain, in northern California. The pH of the drip water was -0.7. The beaker shown here holds 2 liters. Such high concentrations of acid and metals can have severe environmental effects when they enter a river system, since they may kill all aquatic life except microorganisms, for up to several miles downstream.

Such high concentrations of acid and metals can have severe environmental effects when they enter a river system, because they may kill all aquatic life except microorganisms, for up to several miles downstream.

The water molecule is highly cohesive 

It is very sticky, meaning water molecules stick to each other. Water is the most cohesive among the non-metallic liquids.

Water has an amazing ability to adhere (stick) to itself and to other substances. The property of cohesion describes the ability of water molecules to be attracted to other water molecules, which allows water to be a “sticky” liquid.

Hydrogen bonds are attractions of electrostatic force caused by the difference in charge between slightly positive hydrogen ions and other, slightly negative ions. In the case of water, hydrogen bonds form between neighboring hydrogen and oxygen atoms of adjacent water molecules. The attraction between individual water molecules creates a bond known as a hydrogen bond.

Cohesion makes a water drop a drop

It turns out that this surface tension is the result of the tendency of water molecules to attract one another. The natural form of a water drop occurs during the “lowest energy state”, the state where the atoms in the molecule are using the least amount of energy. For water, this state happens when a water molecule is surrounded on all sides by other water molecules, which creates a sphere or ball (perfectly round if it was in outer space).

How Does Water Behave in Outer Space?

This unique picture shows not only a water drop but also an air bubble inside of the water drop. Notice they both behave the same….according to the laws of physics in space. They both form spheres. This makes sense, as without gravity to tug downward, the forces governing the objects are all the same. So, the water drop (and air bubble) form themselves so they occupy a shape having the least amount of surface area, which is a sphere.

On Earth, gravity distorts the shape, but not in space.

On Earth, the effect of gravity flattens this ideal sphere into the drop shape we see. Although you may have heard of a “skin” where water meets the air, this is not really an accurate description, as there is nothing other than water in the drop.

Water has a very high surface tension

In other words, water is sticky and elastic, and tends to clump together in drops rather than spread out in a thin film, like rubbing alcohol. Surface tension is responsible for capillary action, which allows water (and its dissolved substances) to move through the roots of plants and through the tiny blood vessels in our bodies.

You can see capillary action in action (although slowly) by doing an experiment where you place the bottom of a celery stalk in a glass of water with food coloring and watch for the movement of the color to the top leaves of the celery. You might want to use a piece of celery that has begun to whither, as it is in need of a quick drink. It can take a few days, but, as these pictures show, the colored water is “drawn” upward, against the pull of gravity. This effect happens because, in plants, water molecules move through narrow tubes that are called capillaries (or xylem).

Pure water, which you won’t ever find in the natural environment, does not conduct electricity. 

Water becomes a conductor once it starts dissolving substances around it.

Water has a high heat index

It absorbs a lot of heat before it begins to get hot. This is why water is valuable to industries and in your car’s radiator as a coolant. The high heat index of water also helps regulate the rate at which air changes temperature, which is why the temperature change between seasons is gradual rather than sudden, especially near the oceans.

The heat capacity of water is partially responsible for the mild climate along Englands southwestern shore. There are beaches, as at Porthcressa Beach in Scilly, where tropical plants grow.

Air pressure affects the boiling point of water

Which is why it takes longer to boil an egg at Denver, Colorado than at the beach. The higher the altitude, the lower the air pressure, the lower the boiling point of water, and thus, the longer time to hard-boil an egg. At sea level water boils at 212°F (100°C), while at 5,000 feet, water boils at 202.9°F (94.9 °C).

Color and water

The blueness in water is not caused by the scattering of light, which is responsible for the sky being blue. Rather, water blueness comes from the water molecules absorbing the red end of the spectrum of visible light. To be even more detailed, the absorption of light in water is due to the way the atoms vibrate and absorb different wavelengths of light.

An indoor swimming pool appears blue from above. as light reflecting from the bottom of the pool travels through enough water that its red component is absorbed. The same water in a smaller bucket looks only slightly blue, and observing the water at close range makes it appear colorless to the human eye. The details are beyond the scope of this Web site.

Water compressibility allows water fountains to spray water

One property of water is that it is not compressible–you can’t press on it and have it shrink much at all in volume. Just fill a balloon very full with water and then really squeeze it (to compress the water). Instead of the balloon shrinking in size you will end up taking a bath. 

Being incompressible, water makes a handy and useful tool for people to do work (and have fun). Water incompressibility allows fire hoses to work, makes hydraulically-driven tools to function, and for kids to have fun running underneath a fountain that shoots out water (under pressure).

Pictured here is a Retro Systems waterjet computer numerical control (CNC) cutting machine using high pressure water to make a decorative pattern in a piece of metal. High pressure jets of water can be used to cut metal, granite, wood, or rubber to name a few, and is used in various industries, including mining and aerospace.

Hard water

One of the most common causes of cloudy dishes and glassware is hard water. As water moves through soil and rock, it dissolves small amounts of naturally occurring minerals in the form of ions. The most common ions found in hard water are the metal cations calcium (Ca²⁺) and magnesium (Mg²⁺), though iron, aluminum, and manganese may also be found in certain areas.

These metals are water soluble, meaning they will dissolve in water. The relatively high concentration of these ions can saturate the solution and consequently cause the equilibrium of these solutes to shift to the left, towards reactants. In other words, the ions can precipitate out of the solution. This displacement of minerals from the solution is responsible for the calcination often seen on water faucets and pipes, which is a precipitation of calcium or magnesium carbonate.

Multiple rainbows seen at once is a rarity

The common rainbow is caused by sunlight internally reflected by the backs of falling raindrops, while also being refracted at the air/water boundary. There are actually three rainbows in the sky, with three more being seen in the lake reflection.

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