Vending

Cool, i guess I will chime in a bit. My comments in response to the first aticle, esp. the part in the begginning... I completely dissagree with this statement. First off, science cannot exist outside the bounds of philosophy. Philosophy shapes how we view the world and, thusly, how we interpret our observations. One major philisophical point on which science hinges is that the acient past has been govered by the same rules as the present. This concept, called uniformitarianism, is integral to many branches of science, but is not a part of it. Rather it is a philisophical contruct that allows us to apply our current science to the acient past. Another philisophical point which is critical to science: out memories are accurate and so are our observations. There is no proof that we are actually observing anything -- perhaps this is a dream or randoms neurtons firing in our brains. It is a philisopical point that we can trust our observations. The same is true of our memories. (I should add that while it seems unlikely that we would all be having the same delusions, that itself is also a philisophical point.) Still another: Free will (for real! Without this, science is meaningless!). If we are unable to come to our own rational conclusions, then we cannot trust any conclusion stemming from our observations. The list goes on. The point here is that the workings of science rely heavily on philisophical predjudice. Unless we believe that things happen baised on laws, that we can accurately observe the effects of these laws, accurately relate them, and come to rational conclusions about our obvsevations, we cannot perform science as it is practiced today. This is why you cannot seperate science from philisophical predjudice. Science relies to much upon philisophical ideas and ideals. I am somewhat less certain that you cannot seperate out theological predjudice, but I am not quite prepared to talk about that yet. So i will just leave it at perhaps science can be perfomed without theological prejudice. :) As per the second of the articles... It seems to me that the amount of information a human carries (both in his physical make-up as well as in his brain) is quite largee. Transfering this information is equivalent to transfering order, so from a thermodynamic standpoint, the amount of energy required to send a person back must be prodigous. I think that is my only comment about that so far. :cup:

Ok, i have very little to disagree with here, so lets just say that I agree with you so far for the sake of this discussion. OK, so now I have questions. First, I will agree that the partial charge stbilizes the oxygen, but not for the reason you state. The oxygen is stabilized by the partial negative charge because it is more electronegative than the hydrogen. That is it. It has very little, if nothing, to do with the octet. The oxygen already has an octet due to the electron sharing (ie. the covalent bond) with the hydrogens. It cannot have "more" of an octet. As far as it is concerned (from an electron counting viewpoint) it has eight electrons. Given that oxygen has an octet, already, then what leads to the dipole formation? Electronegativities. The idea is that the oxygen holds onto the electrons it shares with hydorgen more tightly than hydrogen does. Thus, there is slightly more electron density on the oxygen than on the hydrogen. NOTICE: The oxygen has more electron density. This has nothing to do with electron count. The point I am trying to make is this; once the bonding orbital is made, then the electrons in that orbital belong to both the oxygen and the hydrogen together, however, the difference in electronegativity can affect the density of the electronic wavefunction around both nuclie. (but the electron count for each maintians the same.) As above; the hydrogen is not a proton, but a hyrogen atom. One with a filled shell. That is, as far at electron counting goes it has 2 electrons (a filled S shell). It did lose electron density to the oxygen, but not electrons. Also, why do you claim that the formation of a positive charge is destabilizing for the hydrogen? It occurs because there is a difference in electronegativity between the oxygen and the hyrodgen. I think you must consider the FULL environment of the hydrogen. In the environment in which the hydrogen is surrounded by oxygens, the hydrogen is MORE stable with a positive charge. We know this must be true, since it occurs spontaneously. Thus, we see that if hydrogen is surrounded by oxygens, it would be unstable for it to carry a neutral or negative partial charge. Actually, the covalent nature of the interaction does just the opposite. Hydrogen bonds are mostly electrostatic in nature. If they were totally electrostatic, they would not exchange or share any electron density at all. However, since the hydrogen bond is to some degree covalent, then it allows sharing. Thus, the covalent contribution to the bond is the only thing that is allowing charge sharing and, therefore, far from limiting it, it maximizes it. To summarize my points and where they disagree with yours; 1) There is no reason why the negative end of the dipole is more stable than the positive end. You have offered not proof of this. Furthermore, your reasoning is flawed, since you do not treat both the oxygen and hydrogen as having a full outershell, which, due to the covlant bond, they both do. 2) The partial covalent nature of the hydrogen bond does not limit the electron sharing in such a bond, but, rather, allows for electron sharing to occur. 3) What do you mean by "the magnetic addition within the orbitals of the oxygen stabilizes the ectra negative charge"? Again, both hydrogen and oxygen have full shells in water. Furthermore, when attempting to discuss the magnetic properties of a atom in a molecule, one must look at the molecule as a whole. Water is dimagnetic as a whole due to the full pairing of electrons in its orbitals. This is due to the covalent bond formation and nothing else. Changes is electronic density do not affect the whether something is dimagnetic or paramagnetic, just the relative intensity of the magnetic feild lines. It is the electronic pairing -- dictated by the orbital structures -- that detrmines gross magnetic properties. As such, it is soley a bonding issue. But perhaps i missunderstand your point? Rather than assuming that water is perfect for life, I think it is better to assume that life is perfect for water. That is; life found a way to use water, not water is nessesary for life. Just a different perspective, that is all.

Seems like most people here are treating the begginner's mind as a good thing...if this were so, then why do we spend so much time learning? that is, why do we devote so much effort to destroying a good thing? Perhaps a begginner's mind isn't all that great after all... With that in mind, the begginner's mind is; A mind that is easily decived A mind that often arives at the wrong conclusion A mind that has no context in which to place information A mind that is undisiplined A mind that does not understand Just a few from me. I do not mean to imply that begginners are bad (hardly, we are all begginners at one time or another and always begginers in somethings). Rather, i just want to point out why we strive to end our begginners mind. My two cents :naughty:

I don't think so. I think chemistry represents a hydrogen bond as a resonance between the ionic and covalent bonds. I don't think that the covalent nature is ever forgot about -- as it is crutial to the behavoir of water. This is, of course, the exact same treatment that can be applied to every "bond" formation. Theoretically, there is really no formal distinction between a covalent and ionic bond (within the resonance formalism at least). That is, the construction of the bond (leading to energy stabilization) is the same in the ionic and covalent cases. Generally, the bond between species A and B can be expressed as the resonance between the structures A B, A+B-, and A-B -- the last being where the electrons lie between the two atoms. Rather, the difference between the ionic and covalent lies in which resonance structure is dominant -- the covalent or the ionic. Given that, you have answered your own question. The question is answered by realizing that the covalent nature of the hydrogen bond is suffeciently strong that the most stable structure of water is not one where the molecules are in van der waals contact. Rather, as is the case with covalent bonding, the most stable spacing is one where the molecules (or atoms) are farther away than the sum of their respective radii. Thus, we see why water expands as it freezes. In the liquid form, the molecules are in van der waals contact -- as they must be if they are a liquid. However, as water freezes, the molecules slow down and they no longer have the kenetic energy needed to overcome the extra binding eneregy that is gained by moving the molecules apart. Consequently, the water molecules are able to adopt their most stable structure -- one in which they are slightly farther apart (owing to the somewhat strong covalent nature of the hydrogen bond). Thus, ice is formed, and is less dense than water. You see, it is the unusually strong covalent component of the h-bond that gives rise to the expansion of water. There is no need to revise the theory or to invoke some sort of "life force." Although i will readily admit that I did not fully follow that part of your post. Perhaps you can expain more clearly what you mean? In particular, I found your discussion of potentials to be confusing and I was unsure as to wether or not you were invoking energetic or electronic potentials. Anyway, i think it remains that the expasion of ice can be understood in the context of currently accepted thoery. At least in my mind :)

Even more, the addition of solutes to a solution ALWAYS raises the boiling temp and lowers the metling point. I don't think so. When water boils, the bubbles are mainly H2O in the gaseous phase. The boiling of water is the physical transition of H2O from liquid to gas. So the bubbles are mainly H2O. By the time that water is boiling most of the gaseous impurities will have already left solution, since the solubility of GASES decreases with increasing temperature (this is of course the opposite trend observed in the case of solid impurites).

I do not agree with your reasoning here. The higher the conductivity, the lower the resistance, the less energy is lost to heat. That is to say that heat is generated by pushing current through a resistor. This is how an electric heating element (as in an electric stovetop) works. You run current through the element which is a resistor and you generate heat. I think that quite the opposite of what you suggest would happen, that is, as you increase the salinity of the solution, you will lower the resistance and, hence, reduce the energy lost to heat. Yakov: For many electrochemical set-ups people us 0.1 molar supporting electrolyte -- i would use at least this much. Also, i do not know exactly what your set-up was, but i would recommend that you move the two electrodes as close together as is possible (but still far enough away to collect the gasses seperately, if that is what you wish. If you are collecting them together, then there is obviously no problems). As you increase the distance between the electrodes you will increase the effective resistance of the circut and you will lose more energy to heat. Just my two cents.

Ever heard of the word "usually"? (hint: look at my post and you will see i used that word when making the statement to which you are replying) (further hint: look up the word usually in a dictionary) -- Sorry, i am done being snide now. Your response just begged for it though. :) Yes, rechargeble batteries exist. yes, some (even most) of them reverse chemical reactions associated with redox events. However, let us remember that rechargeble batteries are designed to be this way. There is a lot of thought put into them. The conditions found within a rechargeble battery are not the conditions found around most redox events at an electrode and they certainly do not parelell the environment found in a AC water electrolysis set-up. Rechargeble batteries are usually designed so that one of the chemical partners (which, is invovled in the chemical reaction that follows the redox event) is present in vast excess. That way when the other of the partners reaches the electrode surface both are garunteed to be present and the reaction will occur. However, I think it is obvious that this situation is not the case in most instances where there is redox events occuring at an electrode. (perhaps it is not so obvious though?) This is only the case when the chemical process following the redox event is a simple one. In the case of complex (multistep and multi-product) reactions this is not usually true. Furthermore, this can only be the case when all the products are in contact with the electrode AND eachother. This is clearly not the case as far as electrolysis of water goes. Here is why; Electrolysis of water produces H2 and O2, but that is not all... The process at the anode produces Oxygen, but that is not all that it produces. The reaction at the anode is... H2O = 4 H+ + 4 e + O2 so we see that not only is oxygen produced, but protons (acid) as well. This acid remains in the aqueous phase while the oxygen moves to the gas phase, thus the two products are not in contact anymore (except for at the gas/liquid interface -- and these only conact the electrode surface in 1 dimension -- so they are, from a practical standpoint, not in contact). This is why you do not see the reverse reaction -- the two products are not incontact with eachother and the electrode in any sort of respectable amount. Likewise for the cathodic process, we have... 4 H2O + 4 e = 2 H2 + 4 OH- again, we do make H2, but we also make aqueous hydroxide. Once again (for the same reasons given for the anode) we do not have the two products in contact with eachother and the electrode and so we do not expect to observe the reverse reaction at any measureable rate. Even worse, in the case of electrolysis, the acid and bases created at the anode and cathode neutralize eachother and so they do not exist any longer, so it is very diffucult to find the reaction partners for H2 and O2. I have already adressed most of the problems with this statement in the above paragraphs, but i thought i would adress one more problem with your thinking. That is this; Redox processes at electrodes involve the introduction of electrons or their removal. Thus, in order for charge not to build up at the surface of the eletrode your medium must be able to conduct either electricity or charge (in the form of electrolytes). Gases (especially netural ones like H2 and O2) do not conduct electricity nor do they contain electrolytes. Thus, if you were to carry out a redox process in a gas you would quickly build up a significant amount of charge on the electrodes. This then becomes a drving force against more like charged being introduced to the electrode and the redox process quickly shuts itself down as the energy required to introduce more charges near the electrode become prohibitive. This is why electrolysis and other electrochemistry is mostly done in liquid in the presense of electrolytes and why you would not expect a quick electrode redox process to occur in a pure H2 and O2 environement. I hope this clears up most of the confusion here. But feel free to ask anyother questions you might have (or raise any concerns you have).

I would like to chime in a bit here to help explain some of the ideas/questions that have been floating around in this thread... 1) Regarding the rate of electron transfer from electrode to chemical. Typically, if one is using a metal electrode (ie. gold or platinum) and small molecules, then the electron transfer is extremely fast. The transfer step itself can be on the order of femptoseconds. This means that the rate of the process is determined by how fast the chemicals can get to the electrode surface -- it is diffusion limited. Diffusion limited processes usually occur on the nanosecond timescale. Thus, we see that for ordinary (60 Hz) AC, the frequency has very little to do with the rate of the redox process. 2) Concerning the reversibility of the reaction. The idea has been raised that perhaps once the the AC current completes a 180 degree phase shift then the reactions might be reversed (ie. those things that have been reduced will be re-oxidised). This is not the case. Usually anytime that a electrochemical event gives rise to a chemical reaction the electrochemical event is irreverible. This is especially the case for dissociation reactions and reactions in which gases are formed (electrolysis of water is both). For dissociations reactions, the two products must once again find eachother at the surface of the electrode in order for the reaction to be reversed (thus this is a three body problem and it is extremely rare that it would occur). For reactions in which gas is released there are two reasons why this would not occur. First, the gases would have to diffuse back toward the electrode, but they are bubbling away. And second, the gases are in a different phase without supporting electrolyte (air doesn't conduct electricity well). 3) Concerning the real reason why the AC electrolysis proceeds more slowly. It is simply a concequence of the ossilating current. That is to say that on a DC circut the voltage is sufficient to break water 100% of the time. In an AC circut the voltage is only sufficient for some part of the time. Thus, a slower rate of electrolysis results just because a there is less time durring which the AC cell is applying suffiecient voltage to eletrolyse the water. I hope this helps clear up a few things :shocked:. Oh, one more thing i should say. Since you are using AC, you will be collecting both H2 and O2 in the same vial -- a situation a bit more dangerous than in the DC case when you are seperating the two out into seperate vials. PS. Great job on the experiment. What an excellent way to answer a question!

I think you are wrong here. Care to explain your answer? It seems to me that all that is needed is the correct potential for the splitting of water. Electron transfer from the electrode is most likely on the micro to nanosecond timescale and so most ossilating currents should not be a problem. But perhaps you have a different reason for you answer?

i think there are an infinite amount of dimensions. Now, how many dimensions are there that have a physical interpritation? That is a whole 'nother question :hihi:

well, I think to give this proper treatment I will have to spend some time thinking about it. So, it may be a while before I post my actual reply to your theory. Just thought I would let you know that I haven't forgot. (it may be weeks, i think)

This is an absolutely horrible benchmark for scientific accuracy. Why would we ever assume that for a scientific theory to be a good one, it must be understood by those outside of the field? Are we too assume that those without a firm understaning of partial differential equations will be able to understand the work being done on turbulat flow of fluids? Is it resonable to expect people who have not studied quantum mechanics to be able to critic the latest work in spintronics? I think not. The simple fact is that people outside the feild of study usually do not have the education nessesary to understand the arguments being made. THis is not a bad thing, but it is the truth. The assumption that if you do not undertand something it must not be true is a very human position to hold, however, it is still remains a poor position. What is your resoning that in order for things to be correct, they must be simple and understandable by an untrained person? I really am curious here. man, i hear this kind of stuff all the time. SO i have a question for you. What was the rate of "really relevent scientific discoveries" 100 years ago? What is it now? What do you mean by really relevant scientific discoveries? There are relevent discoveries occuring all the time these days. The problem is that we do not have the ability to look back on today the way that we can on 100 years ago. They say that hindsight is perfect, but it is also less confusiing and cluttered. The problem with looking for discoveries today is that we are mired in the myriad of scientific data comming forth, whereas when we look at 100 years ago, we have the filter of 100 years. After all that time, it is only the most important things that are spoken about now. Thus, it appears as if 100 years ago everything that was discovered was earth-shattering. Time has filtered out all the floatsom. 100 years from now, it will look like all we did was discover really cool stuff too. Why? Because it is only the cool stuff that people will be talking about.

Well, perhaps "free" critisism was too strong of a phrase. Certianly science is a club of sorts. One that you have to earn membership into. I doubt that many physists would welcom critisism by an impressionist painter as to the validity of quantum mechanics. But then again, most impressionist painters may not care what a physicist thinks of there brush technique ;) What I ment was that the scientific community is suprisingly open to new and different ideas. This does not mean that they accept every new idea presented them, just that if an idea seems usefull enough it is accepted and sometimes other ideas are thrown away. For an movement that is as large as science is and with as much "momentum" as it has, i think it is impressive how many scientific revolutions (ot borrow a phrase form Khun) we have had. But that is neither here nor there. To those that work on the cutting edge of sceintific theory, science tends to look dynamic and open. To those struggling to be accepted by science, it tends to look old and stodgy. Either way though I think most people can agree that there have been several scientific revolutions in the short 300 or so years that modern science has existed (marking modern science as starting with newton -- a resonable position, i think). What other feild of human endevor has been so dynamic over these last few hundred years. Well, i am sure i would find it interesting. However, i have not been formally trained in physics, so I cannot promise that I would understand it completely. However, if you would like to send me a copy of it then you can pm me and we set up a way to get me the document. Or if you just wish to start a new thread, that might work. Either way, I would be more than happy to read your thoughts and give you mine in return :eek: I think I will have fun :) --VM

I certainly hope I did not. Sometimes it is better to have false hope than to have no hope. I think that often times false hope is called "ideals." And in that respect, it is good. I just thought i would give me thoughts so that people did not jump into science with expectations too different from reality. I thiink that a good book for this (one that is readable, entertianing, and shows how science is very much a human endevor) is "The double helix", by James watson. In this he details in very straightforward terms his expereince in dealing with the humanity of science. I do not wish to sound like I think altruism is bad, merely that it is unabtainable. Of course if we don't try to obtain the unobtainable, then we will never know how close we can get...

I am afraid that this would be a false hope. The majority of the behavoirs of scientists is by no means altruistic. Scientists in the real world are dirven by things such as pride, the need for tenure, desire for fame, and spite for other scientists (there are many rivalries in science, not all of them friendly). Science is a human enterprise and, as such, it is directed by human emotion and passions. This is a good thing. There is no way that science would have progressed as far as it has if scientists were not concerned with their pride and reputations. At least that is my opinion. THough it is a common thing for those that do not actively participate in science to romantacize it, i think this is a hendrence more than a help. I have known many people who had a sharp mind withdraw from science after becoming dis-illusioned. They had been lied to throughout their childhoods about the kind men in the ivory towers and were not prepared for the real scientific community filled with egos, petty bickering, and power-plays. The real difference lies in the fact that there is an openess in the scientific community not found in many other areas. The fact that people share most of their results and that these results are open to free critisism is the key to science. This i why it works. But the motivations are not all that different. Alas, science is not so different from other human undertakings. But fortunately for those of us that are scientists, it is really REALLY interesting. :naughty: