exchemist

Well, cookery being a messy process, scientifically speaking, there will a mixture of solids dissolving, the forming of suspensions of solids in liquid as fine particles, and also emulsions of fatty phase liquid in aqueous liquid. But the mechanical action @Externetmentions may also play a role in initially detaching the material from the surface of the pan.

Not sure if the poster will be back, but my bet is this is an aldol condensation.

Yes, I'm sure that works. Possibly the rapid contraction of the surface may loosen whatever is stuck to it as well. However my understanding, as far as cookery is concerned, is a somewhat less violent process, often done after hot fat has been poured off, with the result that the pan is not far above 100C. Supplementary heating may have to be applied to make the deglazing liquid come to the boil. There is a description here, which fits my experience: https://www.thekitchn.com/how-to-deglaze-10807

No, that sounds wrong to me. In cookery, deglazing a pan is the process of dissolving deposits from frying, roasting etc., generally with wine or vinegar best, to form the basis of a sauce or gravy. Nothing to do with kinetic energy. I do this regularly myself when I am cooking. (In the context of diesel engine cylinder liners, deglazing involves renewing the cross-hatched honing pattern on the liners which retains the oil film, by carefully controlled mechanical abrasion. But that is nothing to do with pans or proteins.)

I'm sure you can find information about HBr and HI. There is a more detailed comparison of the relative strength of acidity of the hydrogen halides here: https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_and_Websites_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/2_p-Block_Elements/Group_17%3A_The_Halogens/1Group_17%3A_General_Reactions/The_Acidity_of_the_Hydrogen_Halides A lot of this is taken up with explaining why HF is a weak acid, due to the special effects of hydrogen bonding, which is lost when it ionises, and the negative entropy change on solvation. So there is an argument for treating HF as the odd one out. But you will also find a table of pKa values comparing HF, HCl, HBr and HI which indeed increase as you go down the group. (P.S. In spite of being only a weak acid, HF is highly dangerous as it burns skin and flesh and can penetrate down to the bone, causing serious damage.)

If you count the atoms in the product, what has been lost, compared to those in the two reactants?

This looks like homework. What do you think, first?

But the vapour pressure would be less than atmospheric, until it is at boiling point. So it would be incapable of pushing ice out of the tube, surely?

Sort of. There's just not enough data to settle on one explanation, really. That's often the trouble with these crappy videos on Youtube. Far from aiding understanding, they are designed to bamboozle.

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.