Instead, as the temperature drops the liquid becomes much more "viscous. As this happens, the molecules gradually move more and more slowly, until they are hardly moving at all. This indecisiveness on the part of glass -- choose a state of matter already! There is an enduring urban legend that the glass windows in medieval cathedrals are thicker at the bottom because over hundreds of years, the glass has "flowed" downward and pooled at the bottom.
There is a tiny bit of truth to the legend. At the molecular level, glass does "flow", it just does so very verrry sloooowly. She emphasizes that this is a conservative estimate; it might take much longer. So there's frankly no way in hell that the irregularities in medieval cathedral windows are due to the flowing properties of glass.
Instead, the observed anomalies are probably due to inherent flaws resulting from the manufacturing process. For more detailed information on the molecular structure of glass, whether or not it can be said to truly "flow," and some fascinating early history, see this excellent discussion. In a article in Discover magazine on the physics of glass, Robert Kunzig discussed the possibility of an "ideal glass": "what you would produce if you could cool a liquid with geologic slowness while somehow preventing it from crystallizing.
Physicists have no idea how to even begin visualizing such a thing. But it could be important. We've heard whispers to the effect that discovering an ideal glass transition phase -- namely, a point during the supercooling process where the molecules have no choice but to move rapidly from the disordered liquid configuration to a highly-ordered solid configuration -- could yield insights into the structure of the early universe, which may have existed in a similar amorphous disordered state.
Alas, the news on that front isn't encouraging. A paper in the June 9 issue of Physical Review Letters , by Princeton University's Salvatore Torquato et al , concluded that such an ideal glass transition phase doesn't exist. Torquato's team performed a bunch of computer simulations and couldn't find any such well-defined transition point. Torquato told Live Science that "You could have this continuous change from most disordered to most ordered, and there are an infinite number of possible transition phases between these points.
It puts another nail in the coffin for [the ideal transition] theory. Maybe that ideal transition phase is a bit questionable, but the mysterious "Moosino" over at Chi c'e' in Ascolto reports on a very different kind of "transition phase" from amorphous solid into, well, a million little pieces. Apparently she was driving along one day, when one of the side windows of her car spontaneously shattered.
Being such a well-trained scientist, she nosed around until she found some answers. Basically, the side windows of a car are made of tempered glass, a process that causes the exterior surface to compress while the interior is still expanding a bit. The end result is an exterior compression layer and an interior tension layer -- I believe the technical term is an "inclusion.
The window goes snap! Or crackle! Or pop! Images : top Rice Krispies cereal box. Source: Wikipedia, under fair use. Originally posted in September at the old Cocktail Party Physics site. P W Anderson Donev, F. Stillinger and S. The views expressed are those of the author s and are not necessarily those of Scientific American. Jennifer Ouellette is a science writer who loves to indulge her inner geek by finding quirky connections between physics, popular culture, and the world at large.
The Rice Krispies that leave the factory have very thin, crispy walls and are mostly hollow inside. When the Krispies experience a change in heat, the walls collapse and make that Snap, Crackle, and Pop noise. Do you think cold milk makes your Krispies snap, crackle and pop even louder than if you use warm milk?
Try experimenting. So we might not be able to make our own Rice Krispies at home, but we can certainly use them in our cooking. Pre-heat the oven to c, f, gas 4. While your grown-up is chopping up the nuts, you can get snipping up the apricots using scissors.
Bake in the oven for 28 minutes. William Kellogg won the fight, and in the Kellogg Cereal Company was born. Five years later, with a new process for turning rice into airy, toasted grains, William Kellogg put another iconic cereal on the market. This new cereal, named Rice Krispies, had a distinct characteristic: it made noise when milk was added to the bowl. Unlike oatmeal, boxed cold cereals are precooked, dried, and ready to eat — with or without the addition of milk. Most cereals start as whole grains that are oftentimes processed to remove their outer bran layer before continuing on to become ready-to-eat breakfast fodder.
Depending on the type of cereal being made, those whole grains are either ground into flour or are cooked along with sweeteners, flavorings, and nutritional supplements until they're softened. Rice Krispies fall into the latter category. After cooking, each grain of rice is processed to become that cereal with the famous snap, crackle, and pop. While its puffed rice cousins are made using a pressurized machine that inflates and pop grains, Rice Krispies are simply baked to give them their puffy character.
Cooked and cooled rice, while it still retains some moisture, is partially flattened under rollers — called "bumping. Then in the final step, the grains are rapidly baked in an super-hot oven at about degrees. That extreme heat blast causes each grain to expand and develop air pockets inside the grains called oven-puffing and creates the cereal's delicately crisp texture. So why does it sound like the cereal comes alive when milk is added?
What you're hearing is the sound of those toasted bubbles breaking from the pressure of the milk as it pushes air against those fragile baked grain walls that subsequently shatter. The cereal may have begun as a breakfast food, but about 15 years later Rice Krispie treats, possibly equally as iconic as the cereal itself, got their start.
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