exchemist

Why would this water turn to vapour, though? Boiling water can't boil cold water. I think there is some undisclosed source of pressure in the pipe. It could be water pressure, if this is a pipe connected to a water main. We are not told, and the video snippet carefully cuts off before we can see whether water continues to emerge once the ice plug is out. Or possibly it could be some air pressure built up further along in the pipe, due to freezing and expansion of water within it, causing the air to become compressed. Again we are not told enough. Or it could be something else.

It seems to me fairly pointless trying to speculate on a few seconds of video with no accompanying description of what is going on. (That this video is a continuously repeating loop also adds a certain je ne sais quoi in terms of annoyance value.🙂) Have you any description of what this pipe is, what it is connected to below, etc.

Yes, it's best to think of VB and MO as separate alternative models, each with its strengths and weaknesses. For instance VB gives you more spatial information, for example the idea of electron lone pairs, but has the snag that you have to invoke the rather ropey notion of "resonance" in order to explain the behaviour of some molecules. MO theory is far better at predicting the energy levels, hence spectroscopic and magnetic properties (e. g, the paramagnetism of O₂, which VB fails to predict), and things like the π- bonding in aromatic rings and other conjugated systems, but it gives you less spatial information.

You seem to be mixing MO theory with Valence Bond (VB) theory. The concept of hybridisation, e.g. sp3, comes from VB theory, not MO theory. In MO theory, you would represent F2 as shown in this link: https://www.chemtube3d.com/orbitalsfluorine/ Note that each pair of atomic orbitals combines to give a new pair of MOs and that, in most of these pairs, both the bonding and antibonding MOs are populated with electrons, leading to no net bonding. The overall result is equivalent to a single 2-electron sigma bond. (I only found this website today. I think it is quite cool. You can click the buttons to see the shape of the electron cloud due to each MO.🙂)

The UK has been pretty well 100% Delta for the last few months, as far as I understand. So I think the significance of the latest figures is that they can be taken to be indicative of Delta, specifically. But admittedly I'm just going on a newspaper report (albeit our most reliable newspaper).

Very informative. Thanks. I read in today's FT that the Imperial College React-1 survey has found that vaccination (in the UK a mix of Pfizer and Astra/Zeneca) seems to cut transmission of the Delta variant by half, ie. vaccinated individuals are half as infectious as unvaccinated. So they can still infect a lot of people. It also cuts symptomatic infection: 40% of vaccinated people with a +ve test were asymptomatic, while many others had only mild symptoms. This is consistent with the hospitalisation data in the UK. The vaccines seem to be ~90% effective at preventing disease serious enough to require hospitalisation. So it looks as if the virus will be endemic, though we can hope the incidence of serious disease can be managed through vaccination. However, from your information, and this from the UK, it very much looks to me as if some public health countermeasures to reduce transmission may be needed long term, on top of vaccination. I don't think I'll be throwing away my mask and I think a lot of people will be well advised to continue to work from home as much as they can.

Waves on a string can be also longitudinal, so long as the string is held taut by something elastic at either end, which it is in the setup we are talking about. Why not get 2 empty yoghourt pots, make a hole in the centre of the base of each, pass a string through with a knot at each end to stop it going through the hole and pull the whole thing tight between you and someone else? You will find that, with a string 10m or so long, the person at the far end can speak in a low voice into their pot and, if you hold your pot to your ear, you will hear them quite clearly - through the string. You can prove it by then letting the string go slack and trying again. I did this as a child.

It looks to me as if you are ascribing too much "intent" to the activity of science. I believe it is a misconception to think that science is done in order to enable technology. We do science to satisfy our curiosity about nature, that's all. It is fully expected that solving one problem leads to further ones. But that does not detract from the progress made in solving that first problem. Few people would suggest it is a bad thing that we are curious about nature and want to understand it better. That would be tantamount to an attack on human intelligence.

Indeed. I notice that the gas, interestingly, is specified as being nitrogen - which means that Cp and Cv are known.......

Hmm. Is this presented as a problem involving the ideal gas equation, or could it be an energy problem? (I'm thinking work is done against atmospheric pressure in bleeding gas off.) P.S. I need to run some errands now. Maybe someone will come along who is less rusty on this while I'm away.

Do you know how much gas is bled off, or is the only information you have for the "after" state the pressure?

Aha. So you have been given V. You didn't mention that before. And when you say a calculator, what data would you input to it in order to get the outputs you describe?

Well you are right that if you change n then you can't just use these ratios. There must some other information given, though. What is it?

I've had similar experiences. I haven't researched this but my suspicion is that some hand soaps contain lanolin or other agents to condition the skin (to prevent the soap from depleting the oils in the skin unduly, which can make it dry, crack and cause irritation). I think you are better off using detergent for washing dishes. Shower gel may be OK as well, though I haven't tried it.

There has already been a post, from the resident biology expert, explaining that. There's no need to repeat it.

Yes, it's curious. Out of interest, whose education system are you talking about - if you don't mind saying? I can see the value of mentioning it in the context of the history of the Periodic Table, if you are studying that, but not for the practice of modern chemistry.

Thanks for confirming. I must say I struggled a bit to see what the risk could be, given that hundreds of millions of doses have now been administered, all across the world, with very few issues or side-effects and certainly no reports of the vaccines making people more ill from the virus. But I've come across this ADE schtick elsewhere, peddling by antivaxxers. It may be one of their current stories that is doing the rounds.

Antibody-Dependent Enhancement. From what I read, the issue is when antibodies bind to a virus but fail to neutralise it, which apparently can sometime happen, the virus-plus-antibody complex is ingested by cells in the body as part of the normal destruction process for foreign proteins, but then the virus can detach inside the cell and infect it. So the antibody has actually aided penetration of the virus into the cell. Again, from what I read, the possibility of ADE was checked for in the development of the SARS-CoV-2 vaccines and there is, apparently, no evidence for it. But I may have got this a bit wrong in places so I'd very much welcome comment from @CharonY By the way, this Dr Robert Malone character seems to be misrepresenting his contributions to the development of mRMA vaccines, so he may be a bit of a self-publicist and it may therefore be best to treat what he says on this subject with some circumspection. I quote from https://www.logically.ai/factchecks/library/3aa2eefd: "On his personal website, Twitter, and LinkedIn, Dr. Robert Malone has been promoting himself as the inventor of mRNA vaccines. This is misleading. In 1989, Malone published a paper titled "Cationic liposome-mediated RNA transfection." While this paper is an example of his important contribution to the then-emerging field, it does not make him the inventor of mRNA vaccines. According to Stat News, "for decades, scientists have dreamed about the seemingly endless possibilities of custom-made messenger RNA or mRNA." According to the New York Times, "For her entire career, Dr. Kariko has focused on messenger RNA, or mRNA — the genetic script that carries DNA instructions to each cell’s protein-making machinery. She was convinced mRNA could be used to instruct cells to make their own medicines, including vaccines." While Malone's research may have been important, scientific breakthroughs don't always boast a sole "inventor." Instead, they come about through the work of many. UPDATE: Malone reached out to Logically, stating that he did not invent the mRNA vaccines, but instead the "vaccine technology platform." He also presented us with copies of nine patents – none of which showed that he invented the mRNA vaccines. The judgment for the claim has not changed.

There is a lunatic fringe to both Left and Right, though. The pictures of leftie antivaxxers in the OP obviously belong to such a fringe. What I meant was that we can all chalk up left and right nutcases till the cows come home, but on its own that means little. I suppose the point we are all making in the thread, in our different ways, is that something different and sinister is going on today, viz. that loony ideas seem to have migrated from the lunatic fringe to become mainstream in today's US Republican party. It's Hofstadter's "Paranoid Style", but on steroids. Rupert Murdoch is largely to blame, in my opinion, by treating news as entertainment and thus opening the gates to distorting news without limit, to fit the prejudices of a segment of the viewers. The internet has made it worse, and Trump has capitalised on this to create an entire political movement divorced from reality, that dismisses both science and other evidence-based sources of information when it suits them.

I don't see much point in trying to keep some sort of Left vs. Right "score" when it comes to nutcase ideas. But I do think there is a phenomenon in modern politics whereby, not just science, but professional expertise in general, is considered suspect in significant parts of the political Right. In the UK we've had it over Brexit: Gove's famous comment that "We've had enough of experts", when various economists pointed out the snags. It is obvious in relation to climate change. And now anti-masks, anti-vaxxers etc. It is particularly depressing that simple medical measures have been turned into political totems. There has been a long tradition of anti-intellectualism in Anglo-Saxon culture and perhaps this is just the latest manifestation of it: "Let me have men about me that are fat. Sleek-headed men, and such as sleep o'nights. Yond Cassius has a lean and hungry look. He thinks too much. Such men are dangerous."

Yes, but to get it going again the thing to do is move all the burning surfaces closer together, and then it will heat up and burn more fiercely again.

It takes a lot of heat input to get the fresh side of the log up to burning temperature, which cools the centre of the fire, while the burned side is radiating out into the room and ceasing to burn. And what is worse is you now have cold charcoal which has to be reheated somehow before it can be made to burn once more. But I suppose the way it works out may depend on what kind of log you are burning. Some woods, from coniferous trees, are full of volatiles that burn very readily, so the fresh surface of logs from these may catch relatively quickly, whereas (speaking from experience) others take ages to catch light and some can barely be made to burn at all. But the most intense heat comes from burning charcoal, after the yellow flames have died away.

I agree with this. It has to be borne in mind that charcoal, which is what is left after the volatiles have been driven off and burnt, requires a very high temperature to make it burn. If you turn a partly burnt log so that the charred side is upwards, the charcoal will lose heat and may stop burning. If you want to burn the logs completely to ash you ned to maintain a high temperature in the centre of the fire. Disturbing the logs will increase the temporary heat radiation from the fire but by the same toke will cause it to lose temperature. You may end up with less heat in the end, if the result is a lot of unburnt charcoal left behind. Also, if the logs still have some moisture, you risk actually putting the fire out, by diverting even more heat into evaporating the moisture. I think it is best to keep a really hot centre to any wood fire, which is best achieved by periodically moving the logs closer together as they burn, and not by turning them.

More or less. Mind you one good effect of the privatisation of rail was that we finally got some decent investment in new rolling stock. When BR was a nationalised service the government was scared of investing properly in the trains. But we've ended up with absurdly complex fare deals and lack of integration across different providers. Trying to split the track from the trains, so that multiple companies' trains could run on the same track, never worked properly - and corners were cut on track maintenance, leading to a fatal accident due to no chain of responsibility among contractors and subcontractors. So the track part has been back in public ownership for a while. It's a dog's breakfast. Water seems to be a disaster due to lack of effective oversight from the regulator, on both the operations side and on not stamping on inappropriate financial engineering. But energy and telecoms seem to be a success, so I wouldn't say privatisation has to be a catastrophe for all utlities.

What has happened is the franchise system for rail blew up. Most of the companies were in financial trouble and the pandemic has holed them below the waterline, forcing the government to step in. Franchises have now been abandoned. They may stay in full public ownership, or they may try to get the private sector back in the game in a less risky way, by contracting them to provide a service defined by government and remunerated based on how many trains they run, or something. The London Overground, part of Transport for London's network, uses that model, I believe. But the risk involved in planning and recruiting demand and then investing in the assets to meet it has gone for ever, it seems. Water privatisation has been fairly disastrous. The companies loaded themselves up with debt, using their assets as collateral, and paid their directors and shareholders huge dividends and bonuses while neglecting the basic service they were supposed to be providing. Almost every month now there is a new story of operational mismanagement. Both rail and water privatisations came at the tail end of the privatisation boom started by Thatcher and which finished under Major. While telecoms and energy seem to have worked, more or less, these two never did. Both were privatisations too far.