Category Archives: H2O Chemical Formula

SPLITTING WATER INTO H2 AND O ~ WOW!!!

WATER SPLIT LIGHT
We all know that water is made up of atoms of hydrogen and oxygen, which are chemically combined in the ratio of two hydrogen atoms for every oxygen atom. It usually has a bluish tint and its also tasteless and odourless, but now remarkably a device uses light to split water into clean burning hydrogen.

The following excerpts are from the article, “Device uses light to split water into clean hydrogen”, posted by Mark Shwartz-Stanford, November 15, 2013

CARThe water splitter is a silicon semiconductor coated in an ultrathin layer of nickel and it could help pave the way for large-scale production of clean hydrogen fuel from sunlight, according to the researchers. Their results are published in the journal Science.  The goal is to supplement solar cells with hydrogen-powered fuel cells that can generate electricity when the sun isn’t shining or demand is high.

IMAGEThe image above shows two electrodes connected via an external voltage source splitting water into oxygen(O2) and hydrogen(H2). The illuminated silicon electrode (left) uses light energy to assist in the water-splitting process and is protected from the surrounding electrolyte by a 2-nm film of nickel.  (Credit: Guosong Hong, Stanford University)

Solar cells only work when the sun is shining,” says study co-author Hongjie Dai, a professor of chemistry at Stanford University. “When there’s no sunlight, utilities often have to rely on electricity from conventional power plants that run on coal or natural gas.”   A greener solution, Dai says, is to supplement the solar cells with hydrogen-powered fuel cells that generate electricity at night or when demand is especially high.

HOW TO SPLIT WATER
SCIENTISTSPhoto: Peichuan Shen, PhD student; Shen Zhao, PhD student; and Dr. Alexander Orlov

To produce clean hydrogen for fuel cells, scientists have turned to an emerging technology called water splitting. Two semi-conducting electrodes are connected and placed in water. The electrodes absorb light and use the energy to split the water into its basic components, oxygen and hydrogen.  The oxygen is released into the atmosphere, and the hydrogen is stored as fuel.  When energy is needed, the process is reversed. The stored hydrogen and atmospheric oxygen are combined in a fuel cell to generate electricity and pure water.   The entire process is sustainable and emits no greenhouse gases. But finding a cheap way to split water has been a major challenge…
SILICON SOLUTION
“Silicon, which is widely used in solar cells, would be an ideal, low-cost material,” says Stanford graduate student Michael J. Kenney, co-lead author of the Science study. “But silicon degrades in contact with an electrolyte solution… In STANDFORD U2011, another Stanford research team addressed this challenge by coating silicon electrodes with ultrathin layers of titanium dioxide and iridium. That experimental water splitter produced hydrogen and oxygen for eight hours without corroding.  “Those were inspiring results, but for practical water splitting, longer-term stability is needed,” Dai says. “Also, the precious metal iridium is costly. A non-precious metal catalyst would be desirable.”  To find a low-cost alternative, Dai suggested that Kenney and his colleagues try coating silicon electrodes with ordinary nickel.  “Nickel is corrosion-resistant,” Kenney says. “It’s also an active oxygen-producing catalyst, and it’s earth-abundant. That makes it very attractive for this type of application.”
NICKEL NANOFILM
For the experiment, the Dai team applied a 2-nanometer-thick layer of nickel onto a silicon electrode, paired it with another electrode, and placed both in a solution of water and potassium borate.  When light and electricity were applied, the electrodes began splitting the water into oxygen and hydrogen, a process that continued for about 24 hours with no sign of corrosion.  To improve performance, the researchers mixed lithium into the water-based solution. “Remarkably, adding lithium imparted superior stability to the electrodes,” Kenney says. “They generated hydrogen and oxygen continuously for 80 hours—more than three days—with no sign of surface corrosion.” … “Our lab has produced one of the longest lasting silicon-based photoanodes,” he says. “The results suggest that an ultrathin nickel coating not only suppresses corrosion but also serves as an electrocatalyst to expedite the otherwise sluggish water-splitting reaction… The scientists plan to do additional work on improving the stability and durability of nickel-treated electrodes of silicon as well as other materials.  The Precourt Institute for Energy and the Global Climate and Energy Project at Stanford and the National Science Foundation funded the work.

Article link – http://www.futurity.org/device-uses-light-split-water-clean-hydrogen/?utm_source=Futurity+Today&utm_campaign=aa7a65b600-November_15_201311_15_2013&utm_medium=email&utm_term=0_e34e8ee443-aa7a65b600-206319993

 

WARM OR COLD WATER FREEZES FASTER? ~ DO YOU KNOW?

The following article and responses were posted by George Dvorsky ~ see link at end of blog.

ICEWe may finally know why warm water freezes faster than cool water.

It’s a conundrum that’s baffled scientists since the time of Aristotle: Why do warmer liquids freeze faster than cooler ones? Researchers from Singapore’s Nanyang Technological University have come up with an awesome new theory that may finally put the mystery to rest.

ERASTOIt’s called the Mpemba Effect, and scientists have tossed around a number of theories to explain it.  Some believe that the nucleation temperature of water and the specific impurities it contains determines whether or not the Mpemba Effect will occur. Alternate theories suggest that it may have something to do with certain elements that are in the water, like salt, carbon dioxide, or magnesium. These compounds form a briny muck that causes water to freeze lower and boil higher than it should. And because heating water will shake free some of these substances, the Mpemba Effect can be facilitated.

These aren’t great theories — but they’re the best we got. At least until now.

The Stretching of the Bonds

According to the new study, the Mpemba Effect is caused by a small amount of energy that’s stored in stretched hydrogen bonds.

WATER MOLECULESo here’s the deal: Water molecules have one oxygen atom and two hydrogen atoms, which are held together by covalent bonds — chemical bonds which share a pair of electrons between atoms and a molecule. Then there’s the hydrogen bond to consider; for water molecules, hydrogen atoms are likewise attracted to the oxygen atoms in other nearby water molecules, while water molecules repel each another.

O:H-O bond in water ice. Credit: Xi Zhang et al:WATER ICE BOND

What the researchers discovered was that, as water gets warmer, distance increases between water molecules owing to the repellant force between them. This causes the hydrogen bonds to stretch, and a stretching bond means there’s energy being stored (heating stores energy into the hydrogen bond by shortening and stiffening it) — and this stored energy gets released as the water is cooled, allowing the molecules to get closer to one another. And when molecules get close enough to each other, we get that neat little effect we call cooling, and eventually, freezing.

Now, warm water has more of this hydrogen bond stretching action happening than in cool water. Warm water, therefore, stores more energy — and it has more to release when exposed to freezing temperatures. Which explains why warmer water freezes faster than cooler water.

It sounds like the researchers are really onto something, but it’s just conjecture at this point. Their paper, which appears at the pre-print archive arXiv, still needs to be scrutinized by their peers: “O:H-O Bond Anomalous Relaxation Resolving Mpemba Paradox.”

http://io9.com/we-finally-know-why-warm-water-freezes-faster-than-cool-1458737239

Related link ~ http://io9.com/5505068/decades+long-physics-mystery-sparked-by-ice-cream

THE BASICS OF ION EXCHANGE AND WATER CHEMISTRY

The following excerpts are taken from Water Conditioning and Purification Magazine’s Feb. 2007 article – ‘The Basics of Ion Exchange and Water Chemistry’, by C. F. ‘Chubb’ Michaud, CEO and Technical Director of Systematix Company

ION EXCHANGE PERIODIC TABLE4GIMPIntroduction: Look around: thousands of heavenly bodies in the night sky (comprising a mere fraction of one percent of the known universe), hundreds of cities, millions of houses filled with tens of millions of people. It is somewhat amazing to realize that all of it – every single thing is made up of only three components: electrons, protons and neutrons. ION EXCHANGE PERIODIC TABLE8Each grouping of these components forms a unique Structure we call an element. There are barely 100 naturally occurring elements here on Earth or in stellar space and their collective study is called chemistry. Each compound (water, air, steel, rubber) has its own chemistry. We can predict the properties of most things by studying the unique make up of their components. The chemistry of water is basic but, nonetheless, it is still chemistry. Some people shy away from trying to understand this subject because they feel it’s over their heads. Understanding the fundamentals of chemistry, however, is necessary in order to grasp the full breadth of how certain aspects of water filtration work – particularly ion exchange… The building blocks: In the worlds around us, there are barely 100 elements that occur naturally and, by definition, they are all separate and distinct from one another. Sodium, calcium, sulfur and oxygen are all elements. Elements are made up of a balanced number of positively and negatively charged particles called protons (+) and electrons (-), which, along with neutrons (which are neutral), form an atom of that element. ION EXCHANGE PERIODIC TABLE11The atom was first theorized by Democritus in the 5th century BC and derives from the Greek word for ‘un-cutable’. It is the smallest particle still identifiable as having the properties of the element. Modern science finally accepted this theory but not until the development of nuclear weapons in the 1940s… ION EXCHANGE PERIODIC TABLE

 Recap: By way of a quick summary, all matter is made up of elements (which are made up of electrons (–), protons (+) and neutrons (=). When elements combine, they form compounds. When compounds combine, they can form new  compounds or mixtures. Acids and bases neutralize each other to form salts (and water). ION EXCHANGE PERIODIC TABLE9When salts are dissolved in water, they separate into cations (+) and anions (–) which carry charges (and are, therefore, attracted to other charged substances such as ion exchange resins). Water (H2O) does not ionize as H+ and O– –. Instead, it becomes H+ and OH– (called hydrogen and hydroxyl). These two ions are the backbone of the ion exchange demineralizer reaction (see Reaction 5). In reality, when salts are dissolved in water, they are no longer salts and they are no longer associated with their original partners. It is sort of like a junior high dance. It doesn’t matter who you came in with or with whom you go home, while you are on the dance floor, you’re on your own. ION EXCHANGE PERIODIC TABLE6Thus, if we add sodium carbonate and calcium chloride to water, we produce six different ions: Ca++ (calcium), Na+ (sodium), Cl– (chloride) and CO3 – (carbonate) plus the H+ and OH–. Each ion is free to associate with whatever it feels the most strongly attracted… Introduction to ion exchange: In the above case, the ‘unused’ part of the exchange reaction remains in the water and raises the total dissolved solids (TDS—that would be the Na and the Cl ions). But, what if we could anchor the reactive ions to a solid matrix so we didn’t have to filter them out and their partners would not go into solution to add to the TDS? That is exactly what ion exchange resin does. Ion exchange resins are plastic beads with a built-in reactive partner and an exchangeable ‘soluble’ partner. While the exchangeable partner is free to jump on and off the bead, the fixed reactive partner remains attached. In the case of a softening exchange resin, the partners are sodium (Na+ free to jump) an sulfonate (HSO3– which is fixed). When a calcium salt is introduced (as hard water), the calcium replaces the sodium on the bead and sodium replaces the calcium in the water (on a one-for-one equivalent basis) and there is no increase in TDS and no further filtration needed. The reason this reaction takes place is because the calcium  from the hardness has a higher attraction (divalent) to the exchange resin than does the sodium (monovalent). This is known as ion selectivity and is the backbone of the ion exchange process. As shown by Reaction 5, certain elements or compounds in water can be made to undergo specific selec- tive reactions and these reactions are predictable to some degree according to the element’s family association in the Periodic Table. Divalent ions (those with a double positive charge) such as calcium and magnesium, will react with soap and cause ‘bathtub ring.’ They will also react with the carbonate ion to form scale in pipes and heaters. Although we could precipitate these salts with the addition of carbonate ions (see Reaction 6), we have no easy way to remove the resulting solid except in an industrial setting with large tankage. With ion exchange resins, only the exchangeable ion is soluble or free to move. ION EXCHANGE PERIODIC TABLE10RESINThe counter ion, which is the resin bead itself, is not. This makes the separation after the exchange very easy. In the case of a softener, the resin has an exchangeable Na+. The hardness (Ca++ and Mg++) combined with the resin forms a very strong bond. The water, minus the hardness, passes on through because the resin is retained in the exchange column. Sodium replaces the hardness on an equivalent basis. This means that it will take two sodium ions from the exchange bead to replace a single calcium or magnesium ion. However, on a ppm as CaCO3 basis, this is a one-for-one exchange with no change in TDS (more on this in Part 2)… Conclusion: The Periodic Table of the Elements places all elements into families that help us predict properties and determine similarities. We have shown that there is a preferred coupling of certain elements to form reactions (such as CaCO3 precipitation) that lead us to methods of removing those elements from water. This can be done either selectively (such as in softening) or completely (as in demineralization) utilizing ion exchange resins.

Common elements found in tap water
Aluminum, Calcium, Carbon, Chloride, Fluoride, Iron
Magnesium, Manganese, Nitrogen, Oxygen, Potassium
Silica, Sodium, Sulfur

       

OUR WORLD OF WATER

Physical Properties of Water

 The chemical formula for water is H20, which means it is a molecule consisting of two atoms of hydrogen and one of oxygen. These three atoms are bonded tightly together, more so than the atoms of most other substances. This tight bond and arrangement of atoms in the water molecule results in the following five unusual properties:

The water molecule – two hydrogen atoms and one oxygen atom bonded together

1. THREE FORMS: Water is the only substance that occurs naturally on earth in three forms: solid, liquid, and gas. In liquid water, the molecules of hydrogen and oxygen are close together but are able to slip past one another, which is why it flows. Examples of this are a river, a waterfall, or water coming out of your faucet.

When the temperature drops, the water molecules slow down and become sluggish. As it becomes cold enough for the water to freeze, the molecules rearrange themselves into hollow rings. This is why water expands when it freezes, unlike most other substances which contract. This expansion in the solid phase is the reason why ice cubes float in a glass of water. The ice is actually lighter or less dense than the liquid water.

Water also occurs in the gaseous phase, such as steam rising from a boiling tea kettle. As water is heated, the molecules move about violently, colliding with one another, until some break free and form a vapor, or gas.

EXPERIMENT #1
To see how easily water can change forms, try the following experiment. First melt some ice cubes in a pan on the stove. Bring the same water to a boil and place a cover on the pan to catch the steam. The steam should condense into small dropletsof water when it contacts the cover. Next, place the cover with the droplets of water into the freezer until the droplets freeze. Can you think of how humans use this ability of water to change forms? Think of how you change forms of water when you use it. Find out if it is possible for water to change from a solid form (ice) to the gaseous form (vapor) without becoming liquid.When various materials are dissolved in water, they can change the properties of the water. To see this, take two containers of equal size and put into each the same amount of water. Pour salt into one of the containers, label the container, stir until the salt dissolves and then place both containers in the freezer and mark the time. (Note: Do not use large amounts of water because it will take a long time for this to freeze.) See how long it takes for both to freeze. Can you think of why they put salt on icy roads during the winter? Ask your parents why anti-freeze is important for their car.

2. SURFACE TENSION: Water has a high surface tension. This is the ability of a substance to stick to itself. A drop of water falling from the rim of a faucet will stretch itself very thin before it drops off. Then it immediately forms a sphere and resists any kind of shape change. This high surface tension enables a water surface to support small objects like waterbugs, because their weight distribution will not permit them to break through.

EXPERIMENT #2
Can a needle float on water? Drop a sewing needleinto a container of water and watch it sink. Now, take a strip of paper and make a loop. Carefully rest the needle in the loop and lower it slowly onto the water, being careful not to break the water surface with the needle. Keep pushing the paper down slowly, and gently pull it away after the needle has floated. This may take several tries before it is accomplished. Look very closely at the contact between the needle and the water. Notice the indentation the needle makes on the water surface.Have you ever held water between your fingers? Place the tips of your thumb and index finger together in water. When you pull them out of the water, slowly open up a small space between them. You should catch some water between your fingers and be able to hold it there no matter how you move your hand. See what happens when you open up your fingers. Does the water stay between your fingers? Try this with very soapy water. Can you still capture some of the soapy water between your thumb and index finger? What does the soap do to the surface tension of the water?

3. HEAT CAPACITY: Another unusual property of water is displayed when it is heated. Water has an extremely high heat capacity, which is the ability of a substance to absorb heat without becoming extremely hot itself. This is why it takes a long time for water to boil. An empty pan placed over a hot flame will become red hot and then burn black. However, if some water is placed in the pan over the same flame, the pan will become hot, but not red hot as before since most of the heat will be absorbed from the pan by the water. In like manner, your body cools when you sweat because body heat is absorbed when sweat evaporates.

The heat capacity of water enables the oceans to act as huge reservoirs of solar warmth and keeps our weather from going to great extremes of heat or cold. The moderating effect of water is noticeably absent from a desert, where days tend to be very hot and nights cold.

EXPERIMENT #3
Collect rainwater in a clean glass or metal container and fill another container of similar shape with an equal amount of water from your faucet. Label the containers and place them in a warm place to evaporate. When all of the water has evaporated from both containers, check them for any residue. Which container has the most residue in it after the water evaporates?

4. SOLVENT ABILITIES: The most remarkable aspect of water is its ability to dissolve so many substances; that is, to act as a solvent. For example, some caves form when acidic ground water dissolves limestone bedrock. The substance that is dissolved is called the solute, and the liquid mixture is called a solution. Most water on the earth is actually a solution.

Rainwater is the purest naturally occurring solution of water and contains few dissolved substances.

The degree to which water has a distinctive taste or odor depends on the types of substances dissolved in it. Since water is not changed chemically when it acts as a solvent, it can be recovered for reuse after undesirable dissolved substances are removed. The amount of dissolved substances in water is affected by factors such as water temperature and the nature of the material water moves through.

EXPERIMENT #4
Take two containers of equal size and fill one with cold water and the other with hot water from your faucet. Make sure each container has an equal amount of water. Measure a ¼ teaspoon of salt into each container, stir to dissolve. Keep adding salt by the same amount to each container and see which temperature of water will dissolve the most salt. Keep a record of the number of times you added a ¼ teaspoon of salt to each container. Be sure to stir the water each time you add the salt. What would happen if you dissolved as much salt as possible in hot water and let the water cool to near freezing temperatures? Try this. Do you think that instant coffee or cocoa would dissolve as rapidly in cold water as hot water? Think of some environmental problems related to water’s ability to dissolve so many substances and the effects of dumping hot water containing dissolved pollutants into cooler river water.Mix some salt with water until it has a definite salty taste. Pour this into a pot and bring to a boil. Catch some of the steam using a pan lid. When it cools, taste the water collected on the pan lid. What happened to the salt? Find out what distilled water is and how it is prepared. Why is it best to use distilled water in a steam iron? If all the water in the oceans evaporated, what would be left? Look in an encyclopedia and find out how the Bonneville salt flats were formed.

Streams running through areas where there are few people will generally have a better quality of water than streams running through populated areas. Can you tell why? What do you think happens to the quality of polluted water when it evaporates? How would evaporation act as a natural purifier of polluted water?

CONDUCTIVITY: Conductivity is the ability of a substance to carry an electric current. Water will conduct an electric current only if dissolved ions are present because water molecules do not act as a conductor. Measuring conductivity is a good way to determine the amount of dissolved solids in a sample of water and, thus, to determine its purity.

EXPERIMENT #5
Construct an electric circuit using a flashlight bulb, wire, and a 6-volt dry cell battery. Wire the circuit such that two ends of the wire are submerged in a glass of water, as shown in the diagram. See if the bulb will light up when there is only water in the container. Start adding salt to the water, always stirring. Watch and see if the bulb starts to get brighter and brighter. Do you think that seawater would be a good conductor?

http://www.extension.umn.edu/distribution/youthdevelopment/components/0328-02.html