Hi. I recently completed a course in general chemistry 2. One of the topics discussed thoroughly was electrochemistry. I was actually quite content studying redox reactions, voltaic, galvanic and all the other types of cells. Now I am in general physics 2. We just finished discussing electric forces and electric fields (+ some). Today I am doing an experiment involving electrodes (where I am going to draw the field lines), and the only thing I have on my mind is -e transferring from anode to cathode (assuming this electrode pattern board acts like a voltaic cell). Now, chemistry is all about transfer of electrons. How can this part of physics even be considered physics? If someone could explain the relation between the two subjects in laymen's terms that would be appreciated.
There are a lot of overlaps between the two fields, as there are a lot of overlaps between chemistry and biology, and physics and math. This is evidenced by the fields of Physical Chemistry, Molecular Biology, and Mathematical Physics. So saying ``Chemistry is all about the transfer of electrons'' is overly simplistic. It is mostly about transferring electrons.
Physics describes what the electron is, how it behaves and how it interacts with other particles. The relationship with chemistry is that in principle, by having a physical model of electrons, atoms and molecules, you can then calculate what sorts of chemical reactions will occur as a consequence, as well as details such as reaction rate at various temperatures, pressures and concentrations. Even before the electron was discovered, less sophisticated models of electric charge were still able to make all kinds of predictions and explain certain details about the nature of chemical reactions. So really, chemistry as we know it can be seen as a consequence of physics, and if you go far enough, it specifically comes down to quantum mechanics. The reason chemists aren't simply trained as physicists who then specialize, is because the calculations are far too large and complicated to feasibly simulate the vast wealth of chemical knowledge we've accumulated through experimentation. There is still a great deal of use in a phenomenological approach, where certain properties of various atoms, molecules and reactions are taken as given, and chemists merely worry about the consequences of these properties.
Chemistry is a subset of physics. The main difference being that physics encompasses all matter and energy, while chemistry only concerns itself with the intricacies (pathologies?) of molecules. They build upon each other in practical applications. While you do not need to know Maxwell's equations to build a battery, you can use them to build a good battery. Also, it helps to be able to point to some elegant math that explains what you think you're doing in any realm of science. Thusly, a good background in physics will never hurt the chemist.
To nitpick, yes, it is believed to be so from rational point of view, but strictly speaking I don't think it is completely proven yet. I mean, there are still many complicated chemical laws and phenomena that yet to be explained from first principles.
Ernest Rutherford once said something along the lines of "All science is physics. The rest is stamp collecting." Cocky and demeaning to the other branches, but it does kind of express the idea that ultimately everything boils down to physics.
I'll take your word for it? If you're talking about problems of complexity, some insane level of computational power could give the predictions necessary for some insane arbitrary precision. Protein folding, for example, would be child's play in the hands of a computer 100 years from now. *knock on wood*
In nuclear physics, when we studied the shell model of the nucleus (analogous to the shell model of the electron), the idea is that rather than starting with a precise description of the system built from quantum field theory, or attempting to approximate how each nucleon interacts with every other nucleon, the system can be well-approximated by a central force law, with small corrections for the particles in the outermost shell. We then find that this simple model, and its extensions, can explain many properties of nucleii and the way they decay. When constructing such models to approximate or "smoothe out" the quantum mathematics, we find there are several undetermined parameters that need to be fitted into the model. These parameters could in principle be calculated entirely from the most basic known properties of the constituent particles, but in practice they tend to be found through experimentation. So the idea is we use theoretical physics to derive a simplified, approximate model, and then we appeal to experimentalists to fill in the blanks. Same thing is done with chemistry and predicting chemical reactions, to some extent, and the approach has been very successful so far.
I'm drawing a blank, can you think of any? This isn't to say that examples don't exist, I just can't come up with any from the top of my head.
I'm not a chemist and I said that from an extrapolation. But protein folding comes to mind. The extrapolation I mentioned is based on some examples in physics. Quantum mechanics requires that the Hamiltonian must be self-adjoint, but proving self-adjointness of atom was considered almost impossible until Kato proved it in 1950s. Stability of matter was not settled until 70s, and there is still work going on about stability of boson stars etc. Dirac delta function was given precise meaning only around 50's. Apart from some special cases, Feynman's path integral does not have sound mathematical foundation. We do not know if Standard Model is mathematically consistent. My point is that while deriving everything from first principles with logical rigor is nice, often it is too difficult, and the practical solution is to start somewhere in the middle and build your theory sometimes trading logical rigor with experimental verification. Just because "in principle" you can derive everything does not mean you should look down on other sciences as "stamp collecting". There is more than just collecting and organizing stamps. Looking at the stamps you have, you will guess where to find other hidden stamps, what is drawn on them, how much they cost. As you collect more stamps, you refine the method to guess, and your guess becomes more and more accurate. At some point you discover that all the stamps are made of very tiny stamps, and all the guess-methods you discovered could in principle be derived from the analogous guess-methods for the tiny stamps. In this sense, physics itself is largely stamp collecting too. Edit: To add to that, I think our having sciences such as physics, chemistry, and biology is not accidental, there is something fundamental going on that leads to this classification.
Yeah, I'm not calling it all stamp collecting, like I said that's a cocky and demeaning term. Rutherford was also pissed off that he received the Nobel Prize in Chemistry, he said something along the lines of it being the fastest career change he's ever experienced in his life. Even in the most sophisticated quantum models, you have to plug in parameters taken directly from experiment to make it work, and we don't know how to calculate all of these parameters from deeper first principles. Hopefully by the end of this year I'll understand the basic essentials of QCD, but from what I'm told at present by others, there are plenty of QCD calculations that physicists still aren't able to do.
I am trying to learn lattice QCD too, but there are too many things in the way. From what I read, at least in lattice QCD these problems are mostly algorithmic. I vaguely remember just this summer some people calculated the mass of proton very accurately from lattice QCD.
My Standard Model textbook set up the basics for QCD, explained next to nothing about why it's actually set up that way, and all the actual transition amplitude calculations I did were from the first 6 chapters and involved only the electroweak SU(2)xU(1) sector. Then it started getting into hadrons and parton distributions and stuff, my eyes just bugged out when I saw all that stuff and I figured I'd leave it for the future, since it wasn't needed for the course anyhow.
When I wrote "It is not a priori obvious, rather something you have to prove", I was thinking that although highly unlikely, it is conceivable that some high level phenomenon A is independent from certain list B of low level laws in the sense that * Some fundamental high-level ingredient is necessary to explain A, or, more clearly, * Both A and "not A" are consistent with B, meaning that A is logically independent of B, or * It is not really important to take B as fundamental laws; considerable variations of B also imply A, meaning that A is a universal high level phenomenon.
I'm sorry, Temur. I don't understand the A-B logic. Are you talking about limits of an assumption of common cause? I understand that theoretically we could calculate complex aggregate phenomenon with computational models. This is not to say that we have the models, just that it is theoretically possible. That might sound like theoretically riding a unicorn if we had one, but there are some things even in science we should be optimistic about... that the laws of physics are not selective, but that they are universally applicable--even when minimized. As far as I know: we have no reason to believe that our model of the atom cannot be improved upon, or that an improved model wouldn't then yield better results applied to complex systems. My definition of an improved model is that it does just that. Are we getting off topic? I'm not a physicist, but I really like this thread.
I think this is at least the first point of the A-B logic. I admit this is very nit-picky, and more of a philosophical issue. But the second point is more down to earth, which is to say that the essence of a particular phenomenon is more in the fact that, for instance, the involved object is made of large number of particles, than in the particular laws that govern the individual particles.
Ahh yes. Good point. But here at the university where I study, there are lots of physicists working on the idea of protein folding. Anyway that's just one example. Let me try to motivate Rutherford's comment in the context of modern physics. (TANGENT WARNING!) The question is--at what scale can I safely ignore the nucleus and concentrate on the electrons (i.e. switch from chemistry to physics)? The modern view of quantum field theory is based around the idea of an effective field theory. The essential idea is that, once we pass a specific energy threshold, we never have to worry about the underlying physics. Another way to state this is that we can parameterize nature by certain degrees of freedom, without knowing truly what the underlying degrees of freedom actually are. Using this analogy, it is then clear why we can do chemistry without worrying about the underlying physics, and why we can do biology without worrying about chemistry. Let me give an example: One of the great achievements in the edifice of quantum field theory is the idea that certain parameters depend on the energy at which you measure them. For example, when doing very low energy experiments, the fine structure ``constant'' is approximately equal to 1/137. Add a \(4 \pi^2\) and appropriate factors of \(\hbar\) and c in there, and you get that the coupling of electromagnetism is something like \(1.6 \times 10^{-19} C\). But what if we start banging electrons off of each other at increasing energies? As it turns out, you find a very specific result: once the center of mass energy in the electron-electron collision is larger than twice the mass of the electron, the coupling constant begins to change! As you increase the energy more and more, you find the coupling constant becoming larger and larger. At sufficiently high energies, you start producing strange new particles, like muons, and eventually W and Z bosons. You've just shown experimentally that the theory at high energies no longer is a theory of just electrons and photons---now you have all of these new particles floating around. Even though you are starting with just two electrons, you end up with a whole host of new shit that you have to explain. So even though the theory at high energies and the theory at low energies look qualitatively VERY different, there is a smooth transition from one theory to the other. All of the parameters that you used to understand the interaction of electrons and photons at very low energies can be recovered, and you can understand them in terms of the degrees of freedom of the ``correct'' theory which includes W and Z bosons, and muons and taus. The point is, when you were doing your experiments at very low energies and using \(\alpha = 1/137\), you could calculate things VERY accurately. You didn't need to know about all of the underlying degrees of freedom (muons, taus, W and Z bosons) to make accurate measurements and understand nature. Another example is (as Bork pointed out) nuclear physics. We don't need to know about quarks to do nuclear physics. Nuclear physics is an efffective description of QCD. This is one of the deepest ideas in modern physics, and I think that it can be extended to chemistry and biology. Chemistry HAS to follow from physics, because chemistry is just an effective field theory, of sorts. One studies some system, and introduces some parameters to understand and quantify that system. However, when you study the system at shorter and shorter length scales, you will find that the old parameters can be understood in terms of a new set of more ``fundamental'' parameters. temur's statement, put into this context, amounts to: Does the effective field theory description ever break down? Is it ever true that the degrees of freedom we are using to describe nature somehow don't follow from some more fundamental theory? While I can give you arguments to support the contention that this will never be the case, I can't prove it conclusively. As usual, I have used more words to restate what someone has already said:
