Pressure can melt ice, but not enough…

Countless text books and armchair scientists will tell you that the reason we can skate on ice is that the pressure we apply through the blades of our skates is enough to lower the freezing point of the ice so that it melts and a surface layer of slippery liquid water forms across which the skate can then glide. As with the myth about adding salt to the pan to reduce cooking time when boiling your vegetables, this is patently untrue when you do the calculations.

Certainly, water is an anomalous material, it expands on freezing, which is why ice floats in your G&T and why fish can still swim in lakes and rivers even if they look frozen (it’s usually just a surface layer of ice). Technically one might say that ice is the low-pressure polymorph of solid water with a volume per mole that is about 10% greater than that of liquid water. This 10% difference means that ice and icebergs float, but with 90% of their volume below the surface and only 10% sticking out. Le Châtelier’s Principle thus tells us that the melting temperature (the freezing point) of ice decreases when the pressure applied to the  ice increases. So, ice melts when you apply pressure, but the effect is very small. You need to apply a pressure 121 times that of the atmosphere (1.22 MPa, to be specific) to lower the melting temperature by just one degree Celsius.

Now how does this apply to ice skaters? In his explanatory text, chemist Kevin Lehmann of the University of Virginia tells us to assume in ice skater weighing 75 kg and the skate’s width to be 3 mm and its length 200 mm. “One can calculate that the entire gravitational force exerted on the area of one skate is only a pressure of about 12 atmospheres,” he says. This pressure is an order of magnitude too low to melt ice. Even if we had sharper blades, the maximum effect might be to lower the melting temperature of ice by at most a few tenths of a degree. The ice at an ice rink or hockey stadium is usually well below freezing, so this obviously doesn’t mesh. Skaters can skate even when the ice is very, very cold, so cold that those everyday pressures simply cannot melt the surface to make it slippery. How come?

Unfortunately, it’s one of those as yet unanswered questions as to what makes ice slippery. Scientists have theories concerning the loss of stability of solids at surfaces because there are no molecules “above” for the molecules below to bind to and there are disorder effects that are thought to give rise to surface melting, Lehmann explains. The presence of the skate somehow promotes this effect by bonding to water ice molecules, but it has little to do with the applied pressure. Perhaps the simplest explanation is that the heat generated by friction simply melts the ice. So, how much heat does a skater’s skates produce? Want to do the calculations?

The 5 Ws (and How) of writing for the Web

Steve Buttry presents the five six questions that should guide your reporting as you interview, observe and research to gather the facts for a story, whether that’s live tweeting from a conference, a facebook update, a blog post or your first long-form feature for an online magazine.

They can, he says, also raise ethical issues you should consider as well as helping you home in on links, graphics and people with which to build your article.

The 5 W’s (and How) of writing for the Web « The Buttry Diary.

Tyson autotuned

Neil de Grasse Tyson, that is! Symphony of Science: Onward to the Edge. Fantastic, funny, profound. What more could you want from a science video?

Be sure to stop the video before it gets to 2’56”, otherwise you get the inevitable autotuned Brian Cox, looking wistful and waxing lyrical on a pebble beach in an open-necked shirt…

You can find out more about the wonderful Symphony of Science, which we’ve mentioned before, here.

Ph.Diddy in da house

Grad student Arnold Young, (aka the Ph.Diddy) was an A+ student and is now ready to take over the world of science! He soon discovers how life in the lab is filled with drive and devotion, but frustrations, hard work, late hours, repeated experiments, peer review and striving for respect and recognition. How will the ups and downs of life in the lab shape Ph.Diddy on his journey to have his first scientific paper published?

Video was created by Life Technologies Corp and any proceeds from the video will go to charity, apparently they will ask their Facebook followers to decide which charity.

Improving century-old chemistry of Haber-Bosch

It is a perennial on almost every chemistry course: the Haber-Bosch process for making ammonia. A potassium-doped iron catalyst is heated to several hundred degrees and high pressure nitrogen and hydrogen gas mixed over it to generate ammonia, which is then fed into fertiliser production. The H-B process very effectively traps and fixes nitrogen from the air, and is the industrial equivalent of nitrogen fixation by legumes and living other plants. The process, first demonstrated in 1909, has fed millions of people through the agricultural revolution of the twentieth century. You might say it has allowed our species to become so successful that it now numbers 7 billion…

However, that high temperature, even taking into account the industrial chemical engineer’s need for good quality “waste” heat for distillation towers and the like, is still wasteful. Catalysts that operate at a much lower temperature would be useful. It would also be useful if they could be dissolved rather than being solids, that would improve efficiency considerably given that the bottleneck in the H-B process is the release of nitrogen from the catalyst surface.

I just covered research from Patrick Holland and colleagues at the University of Rochester, New York, USA and the Max-Planck-Institut für Bioanorganische in Mülheim an der Ruhr, Germany, who have developed an iron compound that can promote the H-B process. You can read my full report on the research this week in Chemistry World.

Holland told me a bit more about his hopes for the research:

“I can envision two possibilities [in enhancing the energy efficiency of the H-B process],” he told me. “First, the structural information from our compounds could be used to design new solid surfaces for the H-B catalyst. In this way, we help surface scientists to formulate useful targets for the synthesis of solid catalysts. Secondly, if we could ultimately tune our solution complexes to make a catalyst that turns over many times in solution at room temperature, then it would reduce the high temperatures and pressures that are currently needed in the H-B process.”

I was curious as to what benefits such a catalyst might have over the standard catalysts that have been used and optimised over the last 100 years. “The high temperatures and pressures used in the H-B process place severe requirements on the factory,” Holland added, “after all, they use high-pressure hydrogen at hundreds of degrees Celsius! It is interesting to consider the reasons for these extreme conditions. The H-B process has a delta-G near zero, so the process is thermodynamically feasible but the rate of catalysis is slow. The reason it must be heated is to give an acceptable rate. Because the Haber-Bosch process is entropically unfavourable, the equilibrium becomes unfavourable at a high temperature unless the pressure is raised. So, the only reason for the high pressure is the high temperature that is needed for catalysis! A faster catalyst would work at lower temperatures, and require lower pressures too.”

There are several obstacles to surmount before a new low-temperature catalyst is ever available for ammonia production. “The current obstacles are that we need to make the final hydride product bind dinitrogen to ‘turn over’ [catalytically speaking] and secondly we need to increase the yields of the nitrogen and hydrogen reactions,” Holland told me. He adds that, “We have other related hydride complexes that can be converted into dinitrogen complexes, and so the situation is hopeful with respect to the first point. We are optimistic that by tuning the supporting ligands we can solve both of these problems and converge on a catalytic system.”

Research Blogging IconMeghan M. Rodriguez, Eckhard Bill, William W. Brennessel, Patrick L. Holland (2011). N2 Reduction and Hydrogenation to Ammonia by a Molecular Iron-Potassium Complex Science, 334, 780-783 : 10.1126/science.1211906

Self-closing boxes

Just shine light on these “nets” made from pre-stressed polymer sheet and, according to researchers from North Carolina State University, the nets will fold up into little boxes.

Paper due out in Soft Matter in 2012.

Research Blogging IconLiu, Y., Boyles, J., Genzer, J., & Dickey, M. (2012). Self-folding of polymer sheets using local light absorption Soft Matter DOI: 10.1039/c1sm06564e

Pivot Points

The Euroscientist just published my tenth monthly Pivot Points editorial column, so I thought I’d offer readers a recap on what I’ve discussed over the last ten months and in the three feature articles prior to that: everything from bee colony collapse disorder, the myth surrounding diet cola poisoning and zombie molecules; take your pick:

  • Hazardous chemicals crossing borders – Illicit samples imported
  • Science of sounds – Mark Changizi’s unique explanation of music
  • Addicted to addiction – Tabloid sensationalism and living life to the full
  • Life energy and zombie molecules – The life force and healthy skepticism
  • The big cheese and the director’s cut – Armstrong’s fluff and moon landing truths
  • Cracked conjectures – Mad inventions and maverick theories
  • Is your diet cola blinding? – Aspartame is not the poison claimed
  • Is 10,000 hours practice enough? Practice makes perfect, or does it?
  • Criminal Chemists – Chemists making synthetic highs
  • A, Bee, CCD – What are not the causes of colony collapse disorder?
  • A chemical Christmas – Yuletide fun
  • Interview with Lucy Marcus – Blue skies research – Industry expert opinions
  • Why scientists are waiting for Web 3.0 – The advent of the semantic web

Why are honeybees dying?

There’s a buzz in the world of honeybees. Well, actually, there isn’t a buzz, and that’s the problem, there have been reports across the globe of colony collapse disorder. In Colony Collapse Disorder (CCD) a hive fails to thrive but the beekeepers don’t find the carcasses of their yellow and black striped friends. Given that countless of our essential food crops and some of our luxury foods rely on honeybees for pollination, scientists, beekeepers, and farmers alike are keen to find out what is causing this problem. However, the cause of CCD (Aristotle described contagious brood disease as a “wildness” in bee colonies), has proven an elusive beast.

A new review from the bee research labs at the United States Department of Agriculture, in Beltsville, Maryland, points out that there is as yet no known cause and that, despite activist pressure, it is not necessarily the fault of modern pesticides. This is what the USDA has to say in the review:

A new review would suggest that colony collapse (which was mentioned by Aristotle!) is most certainly a multifactor issue:

“Current hypotheses for CCD focus on the adverse effects of pesticides and other anthropogenic chemicals, poor nutrition, and exposure to novel pathogenic microbes. After initial successes at identifying unusual viral profiles in some CCD colonies, a consensus is emerging that CCD is complex and probably cannot be ascribed to any one agent…Instead, honey bee colonies appear to be resilient to most individual insults, but are vulnerable to the cumulative effects of microbes and other stress factors.”

Research Blogging IconEvans, J., & Schwarz, R. (2011). Bees brought to their knees: microbes affecting honey bee health Trends in Microbiology DOI: 10.1016/j.tim.2011.09.003

Antibacterial hand wash and flu prevention

Antibacterial handwash, wipes, gels etc will not prevent you from catching a cold or influenza. So “flu kits” that claim to be able to protect you from an epidemic are misleading, to say the least. Those diseases are caused by viruses. Indeed, even washing your hands with hot water and soap (antibacterial or otherwise) will not necessarily prevent flu infection, although it is probably a good idea to wash your hands well and regularly to prevent the spread of other infections. You need a vaccine to stop a virus in its tracks; but even those are not 100% effective and depend on getting the right strain before the disease starts to spread.

Handwashing does stop the spread of fecal-oral pathogens, so is a good thing in that regard; make sure you wash your hands thoroughly with soap and hot water after each bathroom visit. But, just to emphasise, handwashing is wholly ineffective in protecting us from droplet- and air-borne diseases, such as measles, chickenpox, influenza, and tuberculosis.

UPDATE: There is evidence that the risk of flu spreading in a building is lower by about 20% if people practice good hand hygiene (an NYT feature article discussed much of the evidence). The same article, however, also cited a Harvard study that suggested washing hands was not as effective at risk reduction as other studies suggested.

 

Personal injury lawyer Max Kennerly was not happy with my original suggesstion, so thanks to him for the NYT article. He added in a subsequent comment, “To be clear, for flu it’s vaccine > hand washing > everything else. Vaccine + good hygiene is always best. Hand sanitizer and surface disinfection don’t do much for flu, but, per the NYT studies, hand washing still does.” Jonathan McCrea of NewsTalkScience was also disturbed by the potential for misinterpretation of my suggesting regarding handwashing. “Few enough people are washing their hands in hospitals as is. Claims that even this basic defence is useless are dangerous,” he said and highlighted garbage headlines from the tabloids as being a case in point.

Elin Roberts complained to the UK’s Advertising Standards Authority, the ASA, about an advert by one manufacturer that claimed its antibacterial handwash offered flu protection. She was told that, “As handwashing was ‘advice’ it was OK.”

 

Blog post originally inspired by Twitter conversation with jjsanderson and JamieBGall regarding a “flu kit” sold by a UK pharmacy that contains antibacterial wet wipes etc.

Creative Commons photo credit: jariceiii

MaxKennerly Max Kennerly, Esq. @ @sciencebase To be clear, for flu it’s vaccine > hand washing > everything else. Vaccine + good hygiene is always best.1 hour ago Favorite Undo Retweet Reply
MaxKennerly Max Kennerly, Esq. @ @sciencebase “hand sanitizer and surface disinfection” don’t do much for flu, but, per the NYT studies, hand washing still does.