John Cuthber

The very first motor, (Mr Faraday's) used DC and a permanent magnet. It also used a pool of mercury as the "sliding" contact so I don't really advise copying it. Here's a comparison. http://www.popsci.com/popsci/how20/252c8c09c166d010vgnvcm1000004eecbccdrcrd.html

"why even bother to post that in here John????" As a joke-OK, I'm a chemist not a comic. BTW, new developments in science often start as contrary opinions- don't be too rough on them.

I think PV = 1/2 MV^2 is the best start but it will not really answer the question. You won't drive a projectile to faster than the speed of sound no matter what pressure and volume you use (unless you do some really complicated things). The speed of sound is roughly the same as the speed as the molecules; if the molecules of the gas are only doing 300 m/s they cannot push a projectile that is moving faster than that because they cannot catch up with it.

The old fashioned approach was to take the sum of the left and right channels which is usually mainly the vocals or the difference between the 2 channels which is largely everything else. Of course this only gives you a mono signal for each and it relies on the idea that the singer is in the middle of the stage.

NH4NO3 can decompose to give N2O and steam, it can also give N2, O2 and steam depending on the conditions- the important fact is that it can do this exothermically so if you get enough of it together it can be made to explode. Adding certain impurities like a fuel or (for some obscure reason) chlorides increases the likelihood of this reaction. The NH4Cl isn't a reactant, but a catalyst. NaNO2 should be pretty dull unless there is some impurity present to act as a fuel.

I don't need a top ten; I just need lots of gold.

Ther are certainly phenolic compounds in a number of drinks. In Whisky (my drink of choice as it happens) the presence of pheolics gives what's called a "peaty" flavour. The off flavour in wine described as "corked" is due to trichloroanisole. (OK, that's not quite a phenol, but it's close.) I think the printed circuit board smell is more like benzoquinone, but it's certainly similar to phenol. Perhaps I should stop sniffing at so many chemicals.

Essentially, its because on one side of the equivalence point it's acid; on the other side it's a base and it has to get suddenly from one to the other.

Ignoring the patronising balderdash in this quote "so where do white people come from, i will tell you but you wont exept it because you have no understanding . i am not here to down you . i am here only to give the truth......... ALBINOS " leaves a question. If white people are descended from albinos how come we white people are not blond haired pink eyed etc? Albino people lack the abillity to synthesise melanin so they are very pale. I accept that a mutation could switch that synthesis back on (the odds are against it but that's another matter). Then you would be back where you started- if you got all the albinos from black families and put them on an island (with a lot of sun-tan oil) after many generations of albinos some of them would revert back to black. What you wouldn't get in a hurry would be white people. You say yourself that albinos in black families don't look like white people then you say that white people are just these same albinos with a bit of black mixed in. That simply doesn't make sense. Allatomear, there's an article in this week's New Scientist about the genetics of skin colour- it's very compicated and they still haven't got it all sorted out yet. These people have been doing the research and I sugest that you read it before making statements like "people have no understanding, i will tell you the truth but thats only if you want to know. first you should learn about genetics and natural selection. your own people hind the truth from you. after you read this, instead of debating get knowledge. read and learn , and then sort out the information ." BTW, the analogy with paint mixing gets used time and again by creationists who don't understand evolution.

I may be missing something here but if I was right about that equation above doesn't the constancy of the speed of light follow from Maxwells equations? And if it does then does that mean that it was Maxwell, rather then Einstein, who first theorised that c is a constant. (OK, that's not how he put it)

Congratulations! You have spotted your teacher's mistake. If you add an acid (and ammonium salts are acids, albeit weak ones) to a mixture of bases like carbonate and hydrogencarbonate, the acid will react with the strongest base first. For what it's worth if you did have carbonate and CO2 present they would react to give hydrogencarbonate Na2CO3 + H2O +CO2 --> 2 NaHCO3 A good way to embarrass the teacher would be to ask why nobody saw the bubbles of CO2 they said had been produced, but I'll let you decide if that's a good idea.

It really depends on the gas. In very cold weather you can work with liquid butane in a class if you want (and I've done it). Similarly in very hot weather (over about 35C) ether boils as soon as you open the bottle. For nitrogen and oxygen (and lots of others) you need to understand critical temperatures and pressures (above the critical temperature the gas will never condense to form a liquid no matter how high the pressure). For nitrogen you need to cool it below -147.1 and compress it to at least 33.5 atmospheres. Not really home experiment territory.

I don't see how a vacuum can, so to speak, "know" that it is moving in order to change its impedance accordingly. If I am running and I hit a tree I will become acutely aware of the relative velocity of the tree and me. How can I measure my speed with respect to a vacuum in order to allow for this when measuring its impedance, permittivity or permeability ?

Saryctos, you say "I think it would have been fine if it had not been played up so much." Er, maybe it's just me but I think that detaining people, many of whom have done no wrong and none of whom is technically guilty; without trial; indefinitely; at the whim of a bunch of soldiers and denying them any prospect of redress isn't "fine" in any set of circumstances, anywhere, ever. Playing it up, down or sideways really isn't the point. There is a very simple way to deal with this mess; find the people who did this and prosecute them for false arrest, false imprisonment, common assault, and so on. If it can be shown that the people who did this were strictly "only obeying orders" (there's a phrase nobody likes to hear) then prosecute whoever gave that order. If that means G.W. Bush does time in jail, good- at least he will have had a fair trial. That would restore the reputation of the law and it might persuade politicians to pay some heed to decent behaviour in future. As for "Just let them back into the country once the war is over?" When, exactly, will the "war on terror" be over, and who signs the armistice?

What's a FIFA? "Cricket, by the way, is a stupid sport, which doesn't hold a candle to baseball." That's a point open to debate. I understand that baseball is a variation on rounders- a game that, here in the UK, kids grow out of when they leave primary school at about 10 years old. However, to be fair, it didn't derive from rounders, we invented baseball first, then rounders. For those unfamiliar with cricket, an explanation the rules can be found here. http://en.wikipedia.org/wiki/Tea_towel_explanation_of_cricket So far as I am aware, there is no explanation of baseball.

I think it says a lot that the the "general stuff" topic is the only one with more posts than the "If you're planning on posting a message insulting us but don't want to bother with any thought or content, please do it in here. " topic. It may be a bit juvenile, but it's probably harmless.

It depends on what you mean by colour. Is "silver" a colour? If you put zinc, which is silver coloured ,into HCl it will dissolve to give zinc chloride, which is colourless (and hydrogen).

There's not any point bothering with a trial. Since the trial would be by millitary personel and their commander in chief has already stated that these are evil men, for the trial to find the poor sods anything but guilty would be insubordination. There's also a potential advantage to permitting evidence gained under torture. (just stay with me here for a minute) You can get anyone to say anything by torture so you can clearly get exactly the evidence you need to convict someone. It's easy, you just pick someone up and beat the s*** out of them until they say what you want them to. Then you get that "evidence" and use it in court. That means that the outcome of the trial will be exactly what the "authorities" want. Since we know all that, those who think evidence gained under torture has any validity must see that the authority is always right. If that's the case then you don't need the trial and you don't need the evidence. If you don't need the evidence you don't need to torture people to get it. In the long run, the acceptance of torture, and those things that follow from that acceptance, means that you don't need to torture anyone any more. I'm suprised Amnesty International are not campaigning for it right now. Of course there's the slight downside of the total lack of any sort of freedom and also of any accountabillity but surely that's a small price to pay for ensuring that torture is redundant. On the other hand you could accept that evidence gained by torture is not only a debasement of any legal process, but logically invalid. How did the US population get suckered into accepting this?

Sweet, or so I'm told; like methanol, chloroform, beryllium salts and lead salts. Of course, all of theses are poisonous so don't bother to try the experiment. No chemicals are harmless- it's always just a question of how harmful. I really wouldn't literally get hold of it since it will burn your fingers.

I'm not entirely sure but I seem to remember that, thanks to Mr Maxwell, you can calculate c from the permittivity and permeabillity of free space. I think it's the square root of 1/epsilon o Mu o (sorry I have't got the hang of Greek characters or subscript zeros here) Since these are porperties of a vacuum and a vaccum can't move it's not suprising that c is constant whether you are moving or not.

Do you mean this? http://en.wikipedia.org/wiki/Space_Shuttle_Columbia#Final_mission

Phenol stinks so I don't advise breathing in the vapour, it also burns the skin and you really don't want it in your eyes. However it's quite commonly used in industry and fairly dilute solutions of it are no worse to work with than lots of other laboratory chemicals. Why do you ask?

"is it possible " No.

"would the shiny side of tin foil work? " Yes.

You could measure the aluminium and work out how much sulphate the aluminium sulphate contributed. A titration using a pH meter as the "indicator" would, I think, give breakpoints corresponding to the titre of H2SO4, HSO4 and Al+++ so that would give quite a lot of information.