|
Ah, water. It's been around all our lives and all our planet's life. So we ought to know everything there is to know about it, right? Not really. Water is probably the most unique chemical in the universe, it's properties are still a mystery to us even after centuries of research. But that shouldn't stop you from gulping it down. Unless you're talking about homeopathic 'medicine'. Throw that in the garbage can right now.
So what's new with H2O? Quite a lot. |
"[Water] is one of the most investigated of all chemicals, but it is still the least understood ... nothing is as complex in its behaviour" - John Emsley, cited in Awake! magazine, (2000)
So what is water? If your answer is “a substance made out of a compound of an oxygen atom and two hydrogen atoms”, then yes, you’re correct. End of article, thanks for visiting!
Oh wait, my administrator had just told me he won’t publish this article as is, and that I have around 1000 words to go. Dang.
Yes, the question might be stupid, but not many people can truly answer it. The answer that was given is correct, but it didn’t answer the significance of water, in physics, chemistry, and of course, biology.
Oh wait, my administrator had just told me he won’t publish this article as is, and that I have around 1000 words to go. Dang.
Yes, the question might be stupid, but not many people can truly answer it. The answer that was given is correct, but it didn’t answer the significance of water, in physics, chemistry, and of course, biology.
Plain Skyjuice?
Water may be one of the most familiar substances on the planet, but it certainly isn’t ordinary. In fact, water’s unique chemical properties make it so complicated that even after decades of research, scientists still have much to learn about this remarkable and versatile substance.
That’s water, as in the clear, sparkling fluid that covers three quarters of the Earth’s surface—not to mention the basis of life as we know it, and possessor of the world’s most recognizable chemical formula (H2O). Water is everywhere. And yet, scientists are still learning about its properties.
Water simply doesn’t behave like other liquids.
If you drop an ice cube into a glass of water, it floats. This happens because water expands as it freezes, which makes the solid form less dense than the liquid. But most other liquids do just the opposite; they shrink and become denser as they freeze, so the solid form sinks. If water behaved that way, ice would accumulate on the bottom of lakes and oceans during the winter, and would have difficulty thawing in the spring. If possible, this would have consequences for aquatic life, and our prehistoric marine ancestors would have been quashed. Grandpa Tiktaalik sure was lucky!
Another surprising characteristic of water is that it boils at a very high temperature—100 degrees Celsius at sea level—compared to similarly sized molecules. If water behaved like other liquids, it would exist as a gas at the temperatures and pressures found on Earth, and life as we know it couldn’t survive.
Water may be one of the most familiar substances on the planet, but it certainly isn’t ordinary. In fact, water’s unique chemical properties make it so complicated that even after decades of research, scientists still have much to learn about this remarkable and versatile substance.
That’s water, as in the clear, sparkling fluid that covers three quarters of the Earth’s surface—not to mention the basis of life as we know it, and possessor of the world’s most recognizable chemical formula (H2O). Water is everywhere. And yet, scientists are still learning about its properties.
Water simply doesn’t behave like other liquids.
If you drop an ice cube into a glass of water, it floats. This happens because water expands as it freezes, which makes the solid form less dense than the liquid. But most other liquids do just the opposite; they shrink and become denser as they freeze, so the solid form sinks. If water behaved that way, ice would accumulate on the bottom of lakes and oceans during the winter, and would have difficulty thawing in the spring. If possible, this would have consequences for aquatic life, and our prehistoric marine ancestors would have been quashed. Grandpa Tiktaalik sure was lucky!
Another surprising characteristic of water is that it boils at a very high temperature—100 degrees Celsius at sea level—compared to similarly sized molecules. If water behaved like other liquids, it would exist as a gas at the temperatures and pressures found on Earth, and life as we know it couldn’t survive.
An Attractive Molecule
In general, the odd behaviours of H2O are reasonably understood. In large part, scientists attribute the unique properties of water to the special chemical linkages it forms called “hydrogen bonds”—interactions between the H’s and the O’s of neighbouring H2O molecules. What isn't clear however, are the fine details of how these bonds form and what they look like in various situations, such as in the presence of chemicals or on surfaces. That’s no easy task because hydrogen bonds are chemical contortionists: highly dynamic, forming linkages that vary in strength and length. And so, even though water influences everything—from how proteins fold inside cells to the weathering of seaside rocks—getting at the fundamentals of its many different interactions is very difficult.
However, water research received a boost when scientists armed with a battery of powerful new tools and perspectives began taking a fresh look at old questions. Because we are nowhere near understanding how water works all of the time in every environment.
Recently, scientists provided some of the most detailed views of water molecules to date. Science magazine took notice, recognizing the collective work of several research teams on water’s structure and chemical behaviour as a top-10 breakthrough of 2004. And although the results have to be verified, some of them challenge conventional wisdom. Indeed, 2004’s discoveries sparked a great deal of interest and healthy debate among scientists. If these results “hold water,” it could change thinking in disciplines as diverse as geoscience, atmospheric chemistry and even biology.
Ions at the Edge
In 2004, scientists tackled the question of where ions—charged particles such as chloride from the salt sodium chloride (Cl - of NaCl), for example—go in a body of water. Conventional wisdom says the surface layers of water repel ions, which are abundant in salty seawater. Consequently, scientists thought such molecules might get buried, going deep into the interior of solutions. But new experimental and computer-generated models from several different research teams indicate the current thinking is wrong. Although they disagree on some of the details, everyone involved concludes that at least some ions are present in the surface layers of water particles. And where there are accumulated ions, chemistry can occur.
In fact, exposed ions on the ocean surface and in aerosols could potentially bind and react with all sorts of chemicals from the atmosphere. Consequently, fog and ocean spray droplets may be more chemically reactive than previously thought. Indeed, recent atmospheric research indicates that is the case. For example, reports suggest that two ions found in seawater—bromide and chloride—trigger chemical reactions that destroy ozone in the Arctic atmosphere. These destructive but natural events occur after wind and waves deposit the chemicals on polar ice and expose them to sunlight. If the 2004 results hold up, atmospheric chemists who have long ignored the contributions of surface ions when modelling conditions such as air quality will have to rethink their calculations.
Water Chemistry
During chemical reactions, molecular parts ranging from tiny subatomic particles like electrons to entire atoms such as hydrogen get shuffled around, transferred, shared and exchanged. Because H2O is the most common chemical solvent on earth, such changes typically require transport through water. However, water is not simply a passive medium in chemical reactions. In fact, it plays an active role, constantly making and breaking chemical bonds around reactive molecules in order to shuttle them from one compound to another. Scientists still don’t precisely know how water accomplishes these tasks. But researchers have developed new tools for isolating and tracking small electron- and hydrogen-containing water clusters to probe these interactions more easily.
The results shed light on a range of extremely common reactions that involve electrons and hydrogen atoms. For example, the oxidations that rust cars and age your skin both involve the exchange of electrons in water. The microbe-fighting and pH-balancing chemistry that keeps swimming pools clean relies on a delicate interplay of electron exchanges and hydrogen transfers. To improve models used in a range of applications, scientists need to understand the fine details about water’s role in chemical reactions such as these. Progress in this area would likely impact a range of fields—from the study of complicated events such as protein folding to the improved design of pharmaceuticals.
In general, the odd behaviours of H2O are reasonably understood. In large part, scientists attribute the unique properties of water to the special chemical linkages it forms called “hydrogen bonds”—interactions between the H’s and the O’s of neighbouring H2O molecules. What isn't clear however, are the fine details of how these bonds form and what they look like in various situations, such as in the presence of chemicals or on surfaces. That’s no easy task because hydrogen bonds are chemical contortionists: highly dynamic, forming linkages that vary in strength and length. And so, even though water influences everything—from how proteins fold inside cells to the weathering of seaside rocks—getting at the fundamentals of its many different interactions is very difficult.
However, water research received a boost when scientists armed with a battery of powerful new tools and perspectives began taking a fresh look at old questions. Because we are nowhere near understanding how water works all of the time in every environment.
Recently, scientists provided some of the most detailed views of water molecules to date. Science magazine took notice, recognizing the collective work of several research teams on water’s structure and chemical behaviour as a top-10 breakthrough of 2004. And although the results have to be verified, some of them challenge conventional wisdom. Indeed, 2004’s discoveries sparked a great deal of interest and healthy debate among scientists. If these results “hold water,” it could change thinking in disciplines as diverse as geoscience, atmospheric chemistry and even biology.
Ions at the Edge
In 2004, scientists tackled the question of where ions—charged particles such as chloride from the salt sodium chloride (Cl - of NaCl), for example—go in a body of water. Conventional wisdom says the surface layers of water repel ions, which are abundant in salty seawater. Consequently, scientists thought such molecules might get buried, going deep into the interior of solutions. But new experimental and computer-generated models from several different research teams indicate the current thinking is wrong. Although they disagree on some of the details, everyone involved concludes that at least some ions are present in the surface layers of water particles. And where there are accumulated ions, chemistry can occur.
In fact, exposed ions on the ocean surface and in aerosols could potentially bind and react with all sorts of chemicals from the atmosphere. Consequently, fog and ocean spray droplets may be more chemically reactive than previously thought. Indeed, recent atmospheric research indicates that is the case. For example, reports suggest that two ions found in seawater—bromide and chloride—trigger chemical reactions that destroy ozone in the Arctic atmosphere. These destructive but natural events occur after wind and waves deposit the chemicals on polar ice and expose them to sunlight. If the 2004 results hold up, atmospheric chemists who have long ignored the contributions of surface ions when modelling conditions such as air quality will have to rethink their calculations.
Water Chemistry
During chemical reactions, molecular parts ranging from tiny subatomic particles like electrons to entire atoms such as hydrogen get shuffled around, transferred, shared and exchanged. Because H2O is the most common chemical solvent on earth, such changes typically require transport through water. However, water is not simply a passive medium in chemical reactions. In fact, it plays an active role, constantly making and breaking chemical bonds around reactive molecules in order to shuttle them from one compound to another. Scientists still don’t precisely know how water accomplishes these tasks. But researchers have developed new tools for isolating and tracking small electron- and hydrogen-containing water clusters to probe these interactions more easily.
The results shed light on a range of extremely common reactions that involve electrons and hydrogen atoms. For example, the oxidations that rust cars and age your skin both involve the exchange of electrons in water. The microbe-fighting and pH-balancing chemistry that keeps swimming pools clean relies on a delicate interplay of electron exchanges and hydrogen transfers. To improve models used in a range of applications, scientists need to understand the fine details about water’s role in chemical reactions such as these. Progress in this area would likely impact a range of fields—from the study of complicated events such as protein folding to the improved design of pharmaceuticals.
Ponder this
Did we took water for granted? It's been around as long as there is life on Earth, and yet we know so little about it. Why?
Being a most ubiquitous chemical, a one that is essential to us and out civilisation, water have been subjected to a lot of pseudo-scientific claims. From homeopathy to a replacement for fossil fuels, water became a magnet for conspiracy theories and consumer fraud. Why is this so?
Discuss
Considering its significance to us, water is still quite a mystery and it's properties are unlike other chemicals known to us. Discuss the history of chemical hydrology, what are the milestones and breakthroughs in the study of water in physics, chemistry and biology?
Further readings
Properties of water, at Wikipedia
Hydrophobic water, as if the thing can't get any weirder. At Phys.Org
Water woo, at RationalWiki
