- 3180 - WATER - strange physics in common water? Water freezes into ice, water molecules suddenly stop moving and begin forming ice crystals with their neighbors. Ironically, they need a bit of heat to do so. You actually need some extra heat to freeze water into ice.
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- This discover adding extra heat to freeze water into ice. was made observing the movement of individual water molecules deposited on a frigid graphene surface. This technique called “helium spin-echo” involves firing a beam of helium atoms at the water molecules, and then tracking how those helium atoms scatter once they ram into the forming ice.
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- The method not only enabled the researchers to collect data from each atom in their experiments, but also helped them record the earliest stage of ice formation, known as "nucleation," when water molecules first begin to coalesce into ice.
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- Nucleation takes place at mind-boggling speeds, within a fraction of a billionth of a second, and as a result, many studies of ice formation focus on the period of time just after nucleation, when patches of ice have already formed and begin to merge into a kind of thick film.
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- Relying on conventional microscopes can't capture what occurs at the start of nucleation, because the instruments aren’t capable of snapping images fast enough to keep up with the speedy water molecules.
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- Scientists sometimes slow down this molecular movement by applying liquid nitrogen to their experiments, lowering the temperature to around minus 418 degrees Fahrenheit, but if you want to observe ice freezing at warmer temperatures, then you need to use this spin-echo. These spin-echo experiments cool the graphene surface to between minus 279 F and minus 225 F.
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- When helium spin-echo applied to water molecules deposited on the graphene, they discovered something counterintuitive. The repulsive interaction from the water molecules not liking each other. When water was put down on the graphene surface, the molecules appeared to repel each other at first, maintaining a degree of distance.
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- The molecules had to overcome this barrier before they could form the islands of ice upon the graphene surface. To better understand the nature of this repulsive force, and how the molecules overcame it, the scientists generated computational models to map out the interactions of the water molecules in different configurations.
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- These models revealed that, upon being placed on cold graphene, the water molecules all orient in the same direction, with their two hydrogen atoms pointed down; the hydrogen atoms in a water molecule stick off from the central oxygen atom like two mouse ears. These water molecules somewhat cluster together on the surface of the graphene, but due to their orientation, a few molecules worth of empty space still persists between them.
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- To bond into ice crystals, the molecules must move a tiny bit closer to one another and break out of their uniform orientation. That forms the barrier, where it will cost energy to nucleate.
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- By adding more energy to the system in the form of heat, the team found they could nudge the water molecules toward each other and allow them to reorient and nucleate forming ice. Adding more water molecules to the system also helped overcome the energy barrier, as the system became more and more crowded.
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- All these interactions take place on incredibly short timescales, so this brief struggle to overcome the energy barrier passes in a flash.
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- Learning exactly how ice forms would be useful in many scientific applications. For instance, with fine-grain knowledge of ice formation, scientists could potentially improve technologies meant to prevent aeronautical equipment, wind turbines and communication towers from icing over.
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- Ice appears on cosmic dust grains and in Earth's atmosphere, and of course in glaciers; so unpacking the physics of ice could have far-reaching relevancy in research.
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- Water is such a ubiquitous molecule, but, it appears there's still so much we don't understand in detail, even though it's a simple molecule. There is still much more to be learned.
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- Water is both extremely familiar making up nearly two-thirds of our own bodies and covering three-quarters of the planet and extremely mysterious. Though you know it so well, many of its properties will completely surprise you. Others are so strange that they still elude scientific understanding.
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- Hot water actually freezes faster than cold water when the two bodies of water are exposed to the same subzero surroundings. And, no one knows why.
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- One possibility is that the “Mpemba effect” results from a heat circulation process called convection. In a container of water, warmer water rises to the top, pushing the colder water beneath it and creating a "hot top." Scientists speculate that convection could somehow accelerate the cooling process, allowing hotter water to freeze faster than cooler water, despite how much more mercury it has to cover to get to the freezing point.
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- Scientists agree that a thin layer of liquid water on top of solid ice causes its slipperiness, and that a fluid's mobility makes it difficult to walk on, even if the layer is thin. But there's no consensus as to why ice, unlike most other solids, has such a layer.
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- Some have speculated that it may be the very act of slipping, or skating making contact with the ice that melts the ice's surface. Others think the fluid layer is there before the slipper or skater ever arrived, and is somehow generated by the inherent motion of surface molecules.
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- Fluid dynamics are so complex that physicists didn't know what would happen to boiling water in zero-gravity conditions until the experiment was finally performed on board a space shuttle in 1992.
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- Afterward, the physicists decided that the simpler fact of boiling in space probably results from the absence of convection and buoyancy two phenomena caused by gravity. On Earth, these effects produce the turmoil we observe in our teapots.
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- When a drop of water lands on a surface much hotter than its boiling point, it can skitter across the surface for much longer than you'd expect. Called the “Leidenfrost effect“, this occurs because, when the bottom layer of the drop vaporizes, the gaseous water molecules in that layer have nowhere to escape, so their presence insulates the rest of the droplet and prevents it from touching the hot surface below. The droplet thus survives for several seconds without boiling away.
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- Sometimes water seems to defy the laws of physics, holding together despite the attempts of gravity or even the pressure of heavy objects to break it apart. This is the power of surface tension, a property that makes the outer layer of a body of water act like a flexible membrane.
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- Surface tension arises because water molecules bond loosely with one another. Because of the weak bonds between them, the molecules at the surface experience an inward pull from the molecules beneath them. The water will stick together until the forces pulling them apart overtake the strength of those weak bonds, and break the surface.
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- A paperclip rests on the top layer of a body of water. Though the metal is denser than water and it therefore ought to sink, surface tension is preventing the clip from breaking the water's surface.
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- When there is a huge temperature gradient between water and the outside air, for example when a pot of boiling water measuring 212 degrees Fahrenheit is splashed into air measuring minus 30 F a surprising effect occurs. The boiling water will instantly turn to snow, and blow away.
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- Extremely cold air is very dense, with its molecules spaced so closely that there isn't much room left over for carrying water vapor. Boiling water, on the other hand, emits vapor very readily. When the water is thrown into the air it breaks into droplets, which have even more surface area for vapor to rise off of.
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- This presents a problem. There's more vapor being emitted than the air can hold, so the vapor "precipitates out" by clinging to microscopic particles in the air, such as sodium or calcium, and forming crystals. This is just what goes into the formation of snowflakes.
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- Though the solid form of almost every substance is denser than its liquid form, due to the fact that atoms in solids normally pack tightly together, this does not hold true for H2O. When water freezes, its volume increases by about 8 percent. This is the strange behavior that allows ice cubes, and even gargantuan icebergs, to float.
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- When water cools to its freezing point, there's less energy causing its molecules to slosh around, so that the molecules are able to form steadier hydrogen bonds with their neighbors, and gradually lock into position; this is the same basic process that causes all liquids to solidify.
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- Just like in other solids, the bonds between molecules in ice are shorter and tighter than the loose bonds in liquid water; the difference is that the hexagonal structure of ice crystals leaves a lot of empty space, which makes ice less dense than water overall.
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- The volume surplus can sometimes be seen in the form of "ice spikes " on top of ice cubes in your freezer. These spikes are composed of the excess water that is squeezed out of a cube by the freezing and expanding ice around it.
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- In a container, water tends to freeze from the sides and bottom toward the center and top, so that the ice expands toward the middle. Sometimes, a pocket of water gets trapped in the middle with nowhere to run, and squirts out of a hole in the top of the cube, freezing in the shape of a squirt.
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- As the saying goes, "no two snowflakes are alike." Indeed, in the entire history of snow, every single one of these beautiful structures has been completely unique. A snowflake starts out as a simple hexagonal prism.
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- As each freezing flake falls, it bumps into a unique range of shape-changing conditions, including different temperatures, humidity levels and air pressures. That's enough variables that the crystal formation never happens in the same way twice.
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- That said, the cool thing about snowflakes is that their six arms grow in perfect synchrony, creating hexagonal symmetry, because each arm experiences the same conditions as all the others.
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- The exact origin of our planet's water, which covers about 70 percent of Earth's surface, is still a mystery to scientists. They suspect that any water that conglomerated on the surface of the planet as it formed 4.5 billion years ago would have evaporated off from the intense heat of the young, blazing sun. That means the water we have now must have gotten here later.
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- During a period around 4,000,000,000 years ago called the Late Heavy Bombardment, massive objects, probably from the outer solar system, hit Earth and the inner planets. It's possible that these objects were filled with water, and that these collisions could have delivered gigantic reservoirs of water to Earth.
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- Comets are chunks of ice and rock with tails of evaporating ice that make long, looping orbits around the Sun are likely culprits for what landed us with all this liquid. There's one problem, however:
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- Remote measurements of the water evaporating off of several major comets (Halley, Hyakutake, and Hale-Bopp) have revealed that their water ice is made of a different type of H20 (containing a heavier isotope of hydrogen) than Earth's, suggesting that such comets may not be the source of all our wonderful water.
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- Ok, then what is the source of our water? And you thought water was simple!
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- 1723 - Water, Water, everywhere. Astronomers have discovered water on Mars, Europa, Ceres, maybe outer space. Follow H2O fingerprints they are trying to learn where all this water came from. Astronomers are discovering water nearly everywhere they look. Water can exist as water vapor, liquid water, frozen ice, or water molecules. In fact ,water can exist in all three states, gas, liquid, solid at the same time, if pressure and temperature are just right.
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- 1620 - What is the likelihood of finding life elsewhere? Water is a key ingredient. How did water arrive on Earth? Where else can we find water for life? On the moon? On Mercury? On Mars? Is there water on other planets?
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- 2888 - WATER - Santa Rosa water? One gallon of Santa Rosa drinking water costs 0.25 cents, four gallons cost a penny. By comparison, bottled drinking water costs $6.00 per gallon. So, why buy drinking water at the grocery store?
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- June 3, 2021 WATER - strange physics in common water? 3179
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