Posts Tagged ‘chemistry’
“You can swim (uncomfortably) in water at a temperature slightly above freezing; a tiny drop in temperature—or a miracle—allows you to walk on water.”*…
As Elise Cutts explains, making ice requires more than subzero temperatures. The unpredictable process takes microscopic scaffolding, random jiggling and often a little bit of bacteria…
We learn in grade school that water freezes at zero degrees Celsius, but that’s seldom true. In clouds, scientists have found supercooled water droplets as chilly as minus 40 C, and in a lab in 2014, they cooled water to a staggering minus 46 C before it froze. You can supercool water at home: Throw a bottle of distilled water in your freezer, and it’s unlikely to crystallize until you shake it.
Freezing usually doesn’t happen right at zero degrees for much the same reason that backyard wood piles don’t spontaneously combust. To get started, fire needs a spark. And ice needs a nucleus — a seed of ice around which more and more water molecules arrange themselves into a crystal structure.
The formation of these seeds is called ice nucleation. Nucleation is so slow for pure water at zero degrees that it might as well not happen at all. But in nature, impurities provide surfaces for nucleation, and these impurities can drastically change how quickly and at what temperature ice forms.
For a process that’s anything but exotic, ice nucleation remains surprisingly mysterious. Chemists can’t reliably predict the effect of a given impurity or surface, let alone design one to hinder or promote ice formation. But they’re chipping away at the problem. They’re building computer models that can accurately simulate water’s behavior, and they’re looking to nature for clues — proteins made by bacteria and fungi are the best ice makers scientists know of.
Understanding how ice forms is more than an academic exercise. Motes of material create ice seeds in clouds, which lead to most of the precipitation that falls to Earth as snow and rain. Several dry Western states use ice-nucleating materials to promote precipitation, and U.S. government agencies including the National Oceanic and Atmospheric Administration and the Air Force have experimented with ice nucleation for drought relief or as a war tactic. (Perhaps snowstorms could waylay the enemy.) And in some countries, hail-fighting planes dust clouds with silver iodide, a substance that helps small droplets to freeze, hindering the growth of large hailstones.
But there’s still much to learn. “Everyone agrees that ice forms,” said Valeria Molinero, a physical chemist at the University of Utah who builds computer simulations of water. “After that, there are questions.”…
More at: “The Enduring Mystery of How Water Freezes,” from @elisecutts in @QuantaMagazine.
Even more at “Cold, colder and coldest ice” (source of the image above)
* Meteorologist Craig Bohren
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As we contemplate crystallization, we might send chilly birthday greetings to a man fascinated by ice and its crystalline structure, Walther Hermann Nernst; he was born on this date in 1864. A physicist and physical chemist, he made material contributions to thermodynamics, physical chemistry, electrochemistry, and solid-state physics. But he is best remembered for the Nernst heat theorem, which stated that the entropy (a thermodynamic measure of disorder) in a system approaches zero as the temperature goes towards absolute zero… which led to the development of what Nernst himself called “the third law of thermodynamics,” and to Nernst’s receiving the 1920 Nobel Prize in Chemistry.
“Food is simply sunlight in cold storage”*…
Increasingly, as Patrick Sisson explains, that’s literally true…
If you had to identify a specific type of real estate that has seen its value increase because of changing consumer eating habits, global demographic shifts, worldwide pandemic preparedness, and US export policy — while its importance to reducing global carbon emissions and adapting to climate change rise in tandem — refrigerated warehouses may not be your first pick.
But there’s a strong case to be made that the expansion and evolution of the cold-storage industry — often called the “cold chain” — will play a significant role in energy, environmental, and economic news in the 21st century. Cold storage facilities aren’t fun places to visit; some are kept so frigid, at minus 50 degrees Fahrenheit, that the workers who toil in these windowless spaces rotate in 15-minute shifts, despite their heavy protective gear…
… refrigerated warehouses are great to build and own. Investors and developers expect 8 to 10% annual growth in this specialized real estate, according to Adam Thocher, SVP of Global Programs and Insights at the Global Cold Chain Alliance (GCCA). That’s made it a profitable real-estate niche…
The ability to more easily cool and freeze food for storage, preparation, and distribution has revolutionized grocery shelves, home cooking, and restaurants for decades, and will continue to do so for years because it taps into every trend all at once. Growing fast-casual restaurant chains, last-mile delivery, a surging global middle class seeking more protein, and the explosion in healthy, organic produce and industrialized frozen food, all need cold storage…
The pandemic accelerated these trends, spiking frozen-food sales in the US to over $74 billion in 2023, a $10 billion increase in just three years, and leading to a wave of refrigerator purchases by Chinese consumers. The need to refrigerate Covid vaccines underscored how important these sites are to global health. Even Ozempic and similar blockbuster anti-obesity drugs need to be stored at 46 degrees F. And the rest of the world is increasingly asking why, if you can always get a Granny Smith apple in New York, can’t you get one in Beijing or London?…
The GCCA estimates there is at least 7.4 billion cubic feet of cold storage worldwide, and 3.7 billion in the US alone, but that’s a vast understatement, Thocher said. The alliance only looks at partial data from 92 countries (not including China) and governments tend to be cagey about sharing his kind of data because of economic and food-security concerns, since these sites are crucial parts of food infrastructure and can reveal levels of economic activity…
Food security has become a global challenge with a growing population, Peters said, especially since roughly 30% of global food production is lost, making increasing supply and reducing food waste imperative. That’s extremely tricky when the critical loss of arable land and desertification, due to climate change, strengthens the case for cold-storage warehouses, which, because of their vast energy use, contribute to that very problem. A 2023 Columbia University study found the sector responsible for 3.5% of total global emissions. The cold-storage industry has responded with more energy-efficient designs and less harmful ammonia-based refrigerants, but it adds an additional challenge to efforts to ramp up sustainable energy production.
“This is a real system-level challenge, a wicked problem,” [Toby Peters, professor of the cold economy at the UK’s Birmingham Energy Institute] said. “My exam question is, how do we feed 9 billion people while economically empowering 400 million small farmers, all without using diesel?”…
Diets, demographics, desertification are all fueling “The Hot Business of Cold Storage,” by @patrickcsisson in @sherwood_news.
* John Harvey Kellogg
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As we chill, we might recall that it was on this date in 1903 that Carl von Linde received two U.S. patents for his Linde oxygen process and associated equipment (Nos. 728,173 and 727,650). Linde had already invented the first industrial-scale air separation and gas liquefaction processes, which led to the first reliable and efficient compressed-ammonia refrigerator (in 1876).
In 1901, Linde had began work on a technique to obtain pure oxygen and nitrogen based on the fractional distillation of liquefied air. His 1903 patents were steps in that direction.
Linde founded a company to commercialize access to these pure gases. Now known as Linde plc (but formerly known variously as the Linde division of Union Carbide, Linde, Linde Air Products, and Praxair), it has become the world’s largest producer of industrial gases– and ushered in the creation of the global supply chain for industrial gases that serves the global cold chain.
“Some say the world will end in fire, some say in ice.”*…
Ethan Siegel reminds us that the world– the living world– almost did end in ice…
… one event came closer than any other to bringing an end to life on Earth: a catastrophe known as either the Great Oxidation Event or the Great Oxygenation Event. Oxygen, one of the hallmark characteristics of our living Earth, was a tremendous destructive force when it first arrived in any sort of meaningful abundance some ~2 billion years after Earth first took shape. The slow alteration of our atmosphere by the gradual addition of oxygen proved to be fatal to the most common types of organism that were present on Earth at the time. For several hundred million years, the Earth entered a horrific ice age which froze the entire surface: known today as a Snowball Earth scenario. This disaster almost ended life on Earth entirely. Here’s the story of our planet’s near-death, culminating in life’s ultimate survival story…
For roughly 300 million years, the Earth was frozen: “What was it like when oxygen killed almost all life on Earth?” from @StartsWithABang in @bigthink. Eminently worth reading in full.
* Robert Frost, “Fire and Ice“
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As we contemplate change, we might send chilly birthday greetings to Raoul Pictet; he was born on this date in 1846. Remembered as a pioneer in cryogenics, Pictet was a Swiss chemist who spent much of his career trying to produce very low temperatures (in order to produce ice for refrigeration)– which led him to the creation of liquid oxygen in 1877 (for which he’s credited as co-discoverer, as French scientist Louis-Paul Cailletet, working completely separately, also produced liquid oxygen that year).
“A lot of people were opposed to it. A lot of people were for it. I myself think about it as little as possible.”
As AI, clean tech, climate response, and other uses grow, concerns are rising that the U.S. and the world are going to run out of electricity (and here). As John Ellis reports, there’s a controversial potential answer closer to hand than many had thought…
Commercial nuclear fusion has gone from science fiction to science fact in less than a decade.
Britain’s First Light Fusion announced last week that it had broken the world record for pressure at the Sandia National Laboratories in the US, pushing the boundary to 1.85 terapascal, five times the pressure at the core of the Earth.
Days earlier, a clutch of peer-reviewed papers confirmed that Commonwealth Fusion Systems near Boston had broken the world record for a large-scale magnet with a field strength of 20 tesla using the latest high-temperature super-conducting technology. This exceeds the threshold necessary for producing net energy, or a “Q factor”, above 1.0.
“Overnight, it basically changed the cost per watt of a fusion reactor by a factor of almost 40,” said Professor Dennis Whyte, plasma doyen at the Massachusetts Institute of Technology (MIT). The March edition of the IEEE Transactions on Applied Superconductivity published six papers ratifying different aspects of the technology.
A poll at the International Atomic Energy Agency’s forum in London found that 65 percent of insiders think fusion will generate electricity for the grid at viable cost by 2035, and 90 percent by 2040.
The Washington-based Fusion Industry Association says four of its members think they can do it by 2030. If the industry is anywhere close to being right, we need to rethink all our energy assumptions…
firstlightfusion.com, cfs.energy, telegraph.co.uk, web.mit.edu, ieeexplore.ieee.org/stamp
From New Items (@EllisItems)
For a series of less-optimistic takes on the prospect of power from fusion: “Why are nuclear fusion reactors difficult?
* Kurt Vonnegut, God Bless You, Mr. Rosewater
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As we ponder power, we might spare a thought for Irène Joliot-Curie; she died on this date in 1956. A chemist and physicist, she followed in the footsteps of her mother (Marie Curie), sharing the Nobel prize in Chemistry (in 1935, with her husband Frédéric Joliot-Curie) for their discovery of induced radioactivity, making them the second-ever married couple (after her parents) to win the Nobel Prize, and making her and her mother the first (and so far only) mother–daughter pair to have won Nobels.
Sadly, Irène also shared her mother’s fate: she died of leukemia resulting from radiation exposure during research.
“In our society (that is, advanced western society) we have lost even the pretence of a common culture”*…
In 1959. C.P. Snow gave a now-famous series of lectures (quickly published): The Two Cultures, lamenting the cleaving of Western culture into spheres of science and humanities, neither of which could clearly understand, thus effectively communicate with the other. Jeroen Bouterse reminds us that Snow had a predecessor…
Several years before C.P. Snow gave his famous lecture on the two cultures, the American physicist I.I. Rabi wrote about the problem of the disunity between the sciences and the humanities. “How can we hope”, he asked, “to obtain wisdom, the wisdom which is meaningful in our own time? We certainly cannot attain it as long as the two great branches of human knowledge, the sciences and the humanities, remain separate and even warring disciplines.”
Rabi had been interested in science since his teenage years, and grown up to be a Nobel-prize winning physicist. He had also been an important player in the Allied technological effort during World War II, as associate director of the ‘Rad Lab’: the radiation laboratory at MIT that developed radar technology. The success of Rad Lab, Rabi later reflected, had not been a result of a great amount of theoretical knowledge, but of the energy, vitality, and self-confidence of its participants. In general, Rabi’s views on science and technology were somewhat Baconian: science should be open to the unexpected, rather than insisting on staying in the orbit of the familiar.
In Rabi’s accounts of his time leading Rad Lab, he would also emphasize the way in which he insisted on being let in on military information. “We are not your technicians”, he quoted himself, adding: “a military man who wants the help of scientists and tells them half a story is like a man who goes to a doctor and conceals half the symptoms.” Indeed, the key to understanding Rabi’s worries about the two cultures – he would go on to embrace Snow’s term – is his view of the role science ought to play in public life. Scientists should not just be external consultants, delivering inventions or discoveries on demand or listing the options available to the non-specialist. In some stronger sense, they should be involved in directing policy decisions.
Even more than Rabi’s positive experience with the military during the war, his views were informed by his frustration with the lack of agency scientific experts were able to exercise in the immediate aftermath. Already in 1946, he complained in a lecture that scientists had been used to create the atom bomb, but they had not been consulted about its use, and the fact that many of them had been opposed to it had made no difference. “To the politician, the scientist is like a trained monkey who goes up to the coconut tree to bring down choice coconuts.”
This feeling would increase with the decision to develop a hydrogen bomb. In 1949, Rabi was one of eight experts in the General Advisory Committee (GAC) to the Atomic Energy Commission (AEC), in which capacity he co-signed a unanimous report arguing that the ‘Super’ should not be built. (Rabi, together with Fermi, signed a minority opinion to the effect that the US should first get the USSR to pledge that it would not seek to develop an H-bomb.)
Rather than signaling to the world that he sought to avoid an arms race, however, President Truman did the opposite: without knowing that it was even possible, he announced publicly that the US would “continue its work on all forms of atomic weapons, including the so-called hydrogen or super-bomb.” Rabi would never forgive Truman…
… in the context of Rabi’s broader thinking about science in modern culture, as he came to develop and express it in the decades after the war [the] was not just that more technical expertise needed to be brought to the decision tables; the point was that scientists should make their moral views heard. In the atomic age, where science created so much power, science’s representatives should wield some of that power. From the perspective of the scientists, this was because the atom bomb had demonstrated beyond doubt that science was not a disinterested search for objective truth; it had consequences, and scientists should accept responsibility for those consequences. They should consider not just the means, but the goals…
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It is a soft law in two cultures discourse that precisely those who most bewail the chasm between science and the humanities end up deepening it. In Rabi’s case, the reason is that he believed in the two cultures; he believed there was something special about the culture and tradition of modern natural science that was a source of wisdom and strength, and that in many ways the project of the humanities was its opposite. Understanding of nature was progressive and forward-looking, was a matter of hope and optimism, while understanding of the human world was old, had already been achieved in ancient societies, and was more a matter of transmission than of innovation. Historian of physics Michael Day notes that over time, Rabi talked less about merging the two traditions and more about putting science at the center of education…
In spite of this, I think Rabi saw correctly that picturing science and the humanities as opposing forces helped him to identify a real fault line in modern culture. The notion that science has to stay on one side of the fact-value-distinction, while the humanities are closer to the actual formation of values, was not a figment of his imagination, and it did stand in the way of his cultural ideals. While not quite the synthesis between the two sides that he sometimes claimed to aim for, the answer he gave – that neither science nor the humanities, nor committees ‘discover’ values, but that values are immanent in activities, in ways of life; that the age of science came with the scientific way of life, with its own values, and that these values were potentially culture-defining – was compelling…
… there remains something inspiring in Rabi’s vision of a common quest for knowledge and understanding, of people working together in activities that are both exciting and important, and of a society that takes those people and their projects not as resources to be exploited, but as models to be emulated.
“The atom bomb and the two cultures: I.I. Rabi on the sciences and the humanities,” from @jeroenbou in @3QD. Eminently worth reading in full.
(Image above: source)
* C. P. Snow, The Two Cultures
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As we search for synthesis, we might send insightful birthday greetings to Walter Kohn; he was born on this date in 1923. A theoretical physicist and theoretical chemist, he shared the 1998 Nobel Prize in Chemistry (with John Pople); Kohn was honored for his development of density functional theory, which made it possible to calculate quantum mechanical electronic structure by equations involving electronic density (rather than the much more complicated many-body wavefunction). This computational simplification led to more accurate calculations on complex systems and to many new insights, and became an essential tool for materials science, condensed-phase physics, and the chemical physics of atoms and molecules.
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