exchemist

Yes I agree it is about what one means by "real". I would contend that those calculational conveniences, and more importantly the concepts which we relate to one another in our calculations, do in the end purport to tell us something about physical existence, i.e. what we think is real, even if they do not claim to be definitive. Otherwise why bother? I think the scientist must believe there is an objective reality out there to be modelled, or he or she would not make the models. To borrow from St. Paul, we may "see through a glass darkly", but surely we have to think we are dimly perceiving something real, don't we?

Yes, up to a point. However I always dislike the tendency to make out physics is all about maths. Physical concepts come before, or simultaneously with, the maths. You have to describe an electron and its properties in words before you can do any maths involving it. So yes, physics makes mathematical models, but the building blocks that the maths connects and manipulates are concepts of physical entities and their attributes that are, of necessity, described in words. The writer quoted also seems to me to somewhat evade the issue about "reality" when she says the wave function is "made up". That suggests it is a fiction. However the fact that this made up maths fits the observations so well shows it is a model of reality that is pretty accurate. So while no one would claim a wave function "is real", the wavelike behaviour it describes does at least represent an aspect of reality.

I bloody well hope so! 😁

Indeed. However, if there is 5-fold degeneracy in the rotational levels (in the ortho spin isomer), would that not be expected to affect the gas phase molar entropy?

It's best not to think of solubility in black and white terms. There are degrees of it. I don't know for a fact, but my guess would be that glycine has appreciable solubility in glycerol, but less than in water. I would expect the same to be true of many other polar compounds. When it comes to ionic compounds (inorganic salts) it may be a more complex picture, depending on the success that a big molecule like glycerol has in binding to a small, charged ion. Others here may have more knowledge of this than I do. But directionally yes, glycerol, being polar, should be able to dissolve polar species significantly.

Interesting. The BBC article doesn't explain how it works but I've found this paper with an abstract and a diagram that help explain this: https://www.sciencedirect.com/science/article/abs/pii/S0306261920311776 Here is the diagram: It seems from this that these microbes generate CO2 and H+ ions by decomposing organic matter below the surface of the soil and in the process release free electrons (!). The electrons are captured by the anode of the circuit. The cathode lies on the soil surface, which is exposed to oxygen in the air. There, H+ ions are combined with oxygen plus electrons from the cathode to produce water. So the net effect is oxidation (electron removal) of the organic matter, producing CO2 underground and water on the surface. The slight mystery is that this paper is from 2 years ago, so it seems unclear why the BBC has decided to report it as news only now.

Well then, since the spin of ¹⁴N is +1, that of ortho N2 will be +2, with potential components +2, +1, 0 -1, -2, so 5-fold degeneracy, vs single states for the para version. I suppose this should show up in entropy calculations for nitrogen in some way.

I suppose there are also in theory spin isomers of other diatomic gases. But probably the spacing between rotational levels is too small for this to produce discernable effects. It’s something I’d never previously thought about.

Ah the light dawns - maybe. I didn't realise that by "extra degrees of freedom" you might have in mind the 3-fold degeneracy of the triplet rotational states. If so then, er, yes, we're saying the same thing!

No. The pitch is determined by the rate at which successive peaks and troughs in the sound waves arrive. The starting and stopping of every syllable of the conversation will also arrive at the same rate, since both are determined by the speed of sound relative to the receiver.

In general I think the Doppler effect would speed up the conversation, just as it would raise the pitch of the speakers. Relativistic time dilation is another thing.

Hmm, I see what you mean. There are no extra degrees of freedom, though. Diatomic molecules all have 2 rotational degrees of freedom. But ortho can only populate odd numbered rotational energy levels while para can populate only even levels. I had to look this up (it's badly explained or not explained in Wiki) but it appears the issue is that ortho hydrogen is a triplet state, in which the total nuclear spin of 1 can be orientated +1, 0 or -1 with respect to the axis of rotation, thereby multiplying the numbers of rotational states available by 3, i.e. each rotational level has 3-fold degeneracy, whereas the para states do not. So at RTP, with kT>> ε for rotation, you end up with a 3:1 ratio, just because there are more ways for ortho to have a certain amount of rotational energy. I think that's it, at least.

It seems to me it's actually quite hard to simulate fast food crap in home cooking. Things like burgers generate massive amounts of smoke, while fried stuff requires a deep fryer and huge amount of oil, which is a nuisance to dispose of. Pizzas are really hard to make, at least if you want a proper pizza base to them, rather than a fake pre-made thing. Cooking proper, simple things at home is quite likely to result in you eating healthily. It is ordering stuff in, because you can't face cooking for yourself, where the problems often seem to start.

For a while at least. Though from what I read, the rotational J=1 state of ortho does eventually relax to J=0 as the ortho gradually converts to para, by the various non-radiative means of relaxation we have been discussing.

The problem with trying to tackle it mechanically is that means quantum mechanically. What has happened is the wave functions of the orbital have become distorted by the nucleus being off-centre. One can't really speak of nice neat forces, acting between the nucleus and electrons as particles, in this scenario. So the energy approach, which is what the Hamiltonian does in Schrödinger's equation, seems to be the only way to describe what happens, so far as I can see. I'm not sure how the heat capacity stuff relates to what we have been discussing. Can you elucidate?

Yes....by creating the transitory fluctuations in magnetic field that I referred to. The way I think of it (rightly or wrongly) is like this. If you consider one nucleus, it is experiencing a magnetic field from the other one in the molecule, so it partially aligns, either with against that field. Standard space quantisation. In a collision, a 3rd nucleus comes up, just as close as the one to which it is bonded, maybe closer. So what magnetic field does the first nucleus now see? Some sort of resultant, with different alignment and different field strength. So it will now try to align with that. But this state has only transitory existence, so its energy levels will be poorly defined (uncertainty principle). And then after the collision the situation reverts to what it was before. But as a result of this there is a probability that the nucleus does not come out of the interaction with the same orientation in which it entered. Regarding centralisation of the nucleus, the electron cloud is centred on the nucleus and if it moves, leaving the nucleus off-centre, the electron cloud becomes distorted, leading to a higher energy state, which is resolved by the nucleus re-centring itself.

The macro is certainly built on the quantum level micro. Much of macro level behaviour is emergent from quantum level behaviour via such things as statistical mechanics.

Thanks, that seems to support my bond breaking hypothesis then.

How interesting. Molecular hydrogen can get adsorbed onto iron compounds and may dissociate on the surface into atoms. If it does that, then I would expect it to prefer to pair up with an atom of opposed spin before desorbing again, since that has the lower of the two energy states. But I'm just guessing about the mechanism.

I would imagine it has to be via emission and absorption of microwave radiation corresponding to the energy of the transition between the two states, as in nmr. Later note: Sorry, no, it can't be. The probability of spontaneous emission at RF frequencies is negligible, because of the ν³ rule. It must be the presence of fluctuating external fields from neighbouring molecules that does it, cf. spin-lattice relaxation in nmr. (This was all a long time ago so my recollection is hazy, to say the least.)

You could start a thread called "Gloss". 😁

No it was a fair cop in that I had been using it to poke fun at a Brazilian crank, which was a bit rude of me. But I wasn't being rude about Brazilians, which is what the mod seemed to think. (I'm quite well in with the local Brazilian community, as it happens.) Anyway, the moral of the story for me is that making assumptions about shared culture is risky.

True. Though we are starting to see them screw up: Trump, Boris Johnson, Erdogan, Putin, Bolsonaro......

Sure. Nativist movements like Trumpism certainly don't tend to come from university students, nor religious fundamentalism.

Isn't that where just about all ideologies start? Certainly true of the Reich example.