16-05-2003 19:41									#151
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quote: My understanding is the C-H bond is covalent, so that you can't make a CH3

You can, but it won't last long. . a CH3 is extremely reactive, a radical, and would instantly react.

	16-05-2003 19:42									#152
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1. There's a piece of fiction I'm working on where the big badguy gets thrown from a Space Elevator (as per Clark) while it is ascending. Assume this happens when the Space Elevator "car" has already left the upper regions of the Earth's atmosphere. What happens to him?

HMB reckons he would fall generally downwards (from the pov of the Space Elevator) plus whatever small sideways velocity he had going out of the SE. Then when the guy reaches the outer surfaces of the atmosphere, gas friction would come into play and he would appear to fly suddenly away from the SE, all the while still falling and possibly burning in a bright and dramatic flash of light upon reentry.

Thoughts? Of course I understand that he will probably be dead by the time he reaches the atmosphere.

2. Say you have eaten far too many beans and you need to pass wind. You are also standing on a set of scales as you do so. Most intestinal gases are composed primarily of methane, which is lighter than air (at normal temperatures and pressures). However, I understand that this gas is under considerable pressure whilst in your body.

In light of the above, would you gain weight or lose weight during the eructative egestory process of farting?

(Note: this is not going into the piece of fiction mentioned in 1. At least, not as far as I'm aware.)

3. If a woman says something in the middle of a forest and there's no man around to hear her, is she still wrong?

	16-05-2003 19:47									#153
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quote: Originally posted by Heresson Well, I'll try to put it in the most gentle way; Are there any mouth/toungue condoms?

I have been reliably told that dental dams are available for people who are female to have oral sex without contracting diseases.

And Heresson, "the most gentle way" is frequently the best way "to put it in".

Edit: added "I have been reliably told" to the start of this post.

	16-05-2003 19:49									#154
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quote: Originally posted by Azazel quote: My understanding is the C-H bond is covalent, so that you can't make a CH3 You can, but it won't last long. . a CH3 is extremely reactive, a radical, and would instantly react.

Wouldn't Cl- be more reactive?

	16-05-2003 19:54									#155
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quote: Originally posted by Alinestra Covelia 1. There's a piece of fiction I'm working on where the big badguy gets thrown from a Space Elevator (as per Clark) while it is ascending. Assume this happens when the Space Elevator "car" has already left the upper regions of the Earth's atmosphere. What happens to him?

He will keep going up with g (acceleration due to gravity) acting downwards, until his velocity wrt to the earth's surface becomes zero. Then he will start falling down.

	16-05-2003 22:38									#156
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Urban Ranger - what happens when he reaches the atmosphere? Will he burn up on reentry? Or would he likely not be travelling fast enough for that?

	16-05-2003 22:55									#157
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That'd depend on how fast the elevator was going, and how high the elevator was, when he was pushed off. When he reaches the atmosphere, he'd continue to accelerate until he goes fast enough such that the drag force on him cancels out the gravitational force, and he reaches his terminal velocity. Along the way, he'd be charred to a crisp due to drag, and finally splatter on the ground.

	16-05-2003 23:27									#158
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Males dont need nipples, but females do.

So when a baby starts to develop it has no gender, yet in the future the females will need the nipples(and the males the penis), so the "basic form" has "prototypes" for both.
When the baby's gender is developed, if it is a female then the nipples are put into use while the clitoris is only a remain of the "penis prototype" that is unneeded in this case, and if it's a male then his "penis prototype" becomes a real penis while the nipples are just there, doing nothing.

	16-05-2003 23:54									#159
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quote: Wouldn't Cl- be more reactive?

I really don't know what is being argued about, but maybe this helps;

The single-bond homolytic dissociation energies at 25C

CH3-H -> CH3 + H requires 435 kJ/mol
HCl -> H + CL requires 431 kJ/mol
CH3-Cl -> CH3 + Cl requires 349 kJ/mol

as for reactivity, it is hard to say that Cl is more reactive than CH3, because it depends on what it is reacting with and at what temperature. Most likely, however, it would react with H from the H2O found everywhere on our planet and at ambient temps (whatever that means). Thus, looking at those number above bond forming of CH4 releases 4 kJ/mol more energy than does the forming of HCL.

Yes, they are both highly reactive free radicals.

	17-05-2003 02:07									#160
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Urban:

quote: Depending on the electronegativity of carbon and hydrogen, a chemist might be able to coax the reaction to use up more carbon, thus freeing up some hydrogen gas. Of course, this is just a wild guess.

You mean something like
2FeO + CH4 -> 2Fe + CO2 + 2H2?

Thermodynamically unfavourable, unfortunately...

H2 is not a terribly stable molecule, so in order for the reaction to proceed you need to use the H2 in a reaction of some kind.

quote: Nah, you overestimated me

Well, I can imagine worse things

quote: Yes, that's the main point. I was also thinking along the lines of additional electric characteristics of a battery, that it has an internal capacitance. So, in addition to the chemical reaction, it could store up some electricity as well, giving it a bit of an extra kick. Of course, I have no idea how big that would be.

I don't think it can... The capacitor in an electronic device is based on the Coulomb attraction between the plates, isn't it? There aren;t any capacitors in the battery, so I don't think the electric energy can be stored.

	17-05-2003 02:43									#161
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quote: Wouldn't Cl- be more reactive?

No, Cl- is quite happy the way it is. Remember, ordinary ocean water contains about 3 weight% chloride ions... Not to mention the other half of table salt, NaCl.

There's a big difference between ionic and radical chemistry, though. When you talk about homolytic bond cleavages you assume that you get radicals. This is very useful for comparing the thermodynamics of potential reactions. But it doesn't say anything about the patway to get there.

It's like comparing the relative height of two places - knowing that place A is 10m above sealevel and place B is 5m above sealevel, you can immediately say that place A is 5m higher than place B, right? But that doesn't mean that if you put a soccer ball in place A it will automatically end up in place B - if there is a hill in the way it won't get over it. Place A would be a "local minimum", while place B is the "global minimum". See what I mean?

The hill in the case of methane is the very high energy of either
CH4 -> CH3(radical) + H(radical)

or

CH4 -> CH3(anion) + H(cation)

or

CH4 -> CH3(cation) + H(anion)

In the gas phase, this reaction is the easiest:
CH4 -> CH3(radical) + H(radical), with an energy of +435 kJ/mol.

In an aqueous solution, this reaction is easiest:
CH4 -> CH3(anion) + H(cation), with an energy of +337kJ/mol.

Still, 337 kJ/mol is not going to happen... It would require temperatures of about 1000 degrees C, and since the boiing point of water is 100 C...


Now compare to HCl.

In the gasphase, the homolytic cleavage is the easiest, and if we use Japhers numbers again, we have

HCl -> H(radical) + Cl(radical) requires 431 kJ/mol

But in an aqueous solution, this reaction is much easier:
HCl -> H(cation) + Cl(anion), which actually generatesenergy, -38kJ/mol.

See the difference?

	17-05-2003 02:44									#162
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(btw, assuming that the H(cation) is solvated in the above examples)

	17-05-2003 03:04									#163
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How do adhesives work? What makes stuff sticky? What determines how strong a glue is? How does stuff like blutack/rubber cerment work?

	17-05-2003 03:21									#164
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quote: Originally posted by DanS Do you think that dental jobs are expensive here? $100 is nothing. A trip to the dentist, cleaning, and a quick look by the dentist costs you $120 here.

A checkup at the dentist is free for me but that's just because my daddy is a cardiologist, and he has friends everywhere in the medical bizness, including a wide selection of dentists and the like... And between doctors (and close relatives) checkups are always free, so if that dentist wants his heart checked, my daddy will do it for free as well...

But for normal people a simple checkup is pretty cheap, most of it they get back from social security (hey that's what Belgium is renowned for ), and it is also the reason why people in Belgium just go to the doctor whenever they feel like it, even if they have a mere scratch, or if their finger itches a bit (seriously, my dad once had this freak who came in thru the emergency entrance in the hospital complaining about an itching finger )

Also, instead of going to a normal doctor, lots of people prefer to go directly to specialists (such as cardiologists like my dad) because social security payz anyway


It has advantages (a ****ing cheap medical system, except when you have rare diseases that are not on the medical care refund list, but that's where charity money is going to)
but disadvantages as well... Belgium uses about 4 times as much antibiotics as our neighbour Holland (and everybody knows that in most cases, antibiotics are useless), and actually we use enormous amounts of medicines in general, just because joe jackson here "expects" to get medicines when he pays a visit to the doctor, even if he's not really sick, or if he just has a cold... And in many cases, patients are unhappy if their doctor doesn't prescribe medicines, and they just go to another doctor, that !does prescribe them pillz . This results in an unhealthy situation of competition between doctors in order to keep patients, all the more because regular doctors here earn as much as a city street cleaner or something


Btw Eli: you're absolutely right on the nipples, I was just about to post it!

	17-05-2003 03:38									#165
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Stinger: Ships in Star Trek seem upright because they're aligned to the surface of the nearest relevant planet. In this case it's "Earth" from whose surface they float using specialised engines called "wires", sometimes as high as several metres above the ground.

	17-05-2003 05:40									#166
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If a human was conceived and grown until full maturity all in space what would he look like when he was done growing?

	17-05-2003 05:47									#167
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Isaac Asimov wrote an essay on longevity. He had the key to comparing various species: normalize lifespan to heart rate. When you do that most species lifespan is around 1 billion heartbeats. Human lifespan is around 4 billion, great apes 2 billion. The real statistical outliers are the parrots, some living 8-10 billion heartbeats.

	17-05-2003 05:53									#168
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Good point CyberGnu, I was always think chloride gases. The actual state of the chemical does come into play. Aqeous = definitly stable, NaCl definitly stable - yet Cl- would not exist as a free radical in a crystaline latice... anyway.

Processes to create H2 are tricky since H bonds stringly with almost anything that is easy to take it off of... Fuel cell science is at the leading edge not only of chemisty, but material science, and it will be interesting to see what happens.

quote: How do adhesives work? What makes stuff sticky? What determines how strong a glue is? How does stuff like blutack/rubber cerment work?

Has something to do with viscosity and coehission forces such as surface tension. That is a good question, but I am to drunk to care... Sticky stuff is kewl though.

Oh yeah, on the battery stuff, I heard that there is a battery out there in which one of the solutions contains some kind of magnetic metal suspended in it. When an electrical current is applied through that anode/diode that it draws on the magnetic properties of these metals. Once the anode/diode is completely plated by these particals the battery is essentially dead. Yet, when an electrical current is not present these metal particals begin to fall off of the battery until complete absorbed back into the solution = self recharging batteries... Pretty cool huh?

	17-05-2003 05:59									#169
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Actually, all human beings are by default female It takes a set of hormones very early in the womb to transform the basic female form into the male form. I guess the need to get rid of nipples never came up evolutio wise, so why go through the effort?

	17-05-2003 11:27									#170
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What happens on the molecular level at the edge of a blade?

	17-05-2003 19:09									#171
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quote: Originally posted by CyberGnu Urban: You mean something like 2FeO + CH4 -> 2Fe + CO2 + 2H2? Thermodynamically unfavourable, unfortunately... H2 is not a terribly stable molecule, so in order for the reaction to proceed you need to use the H2 in a reaction of some kind.

Well, there are lots of factors you can vary though, say, temperature, presence of catalysts, rate of flow, concentration, etc. You could even try mixtures of things, what happens if CO or water vapour is present, say?

quote: Originally posted by CyberGnu I don't think it can... The capacitor in an electronic device is based on the Coulomb attraction between the plates, isn't it? There aren;t any capacitors in the battery, so I don't think the electric energy can be stored.

The battery is sort of like a capacitor though.

	17-05-2003 19:13									#172
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quote: Originally posted by johncmcleod If a human was conceived and grown until full maturity all in space what would he look like when he was done growing?

He would look like a normal person, except without the effects of gravity. So, for example, his muscles are weak, and his bones is like glass.

	17-05-2003 19:15									#173
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quote: Originally posted by Alinestra Covelia What happens on the molecular level at the edge of a blade?

Not sure what your question is. AFAIK, the material stays the same, just that there's less "stuff" there, so the cross section area decreases.

	17-05-2003 19:19									#174
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It seems I am outgunned by the PhD student Cybergnu, and the Chemical engineer Japher.

	17-05-2003 19:21									#175
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Don't feel bad

	17-05-2003 19:35									#176
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quote: Originally posted by Oerdin I've seriously wondered why people in the green movement haven't embraced nuclear power. It produces very little pollution and solves, what many of them considered to be, the great threat to the world today, global warming. I don't think GW will be nearly as big an issue as the pundits say but I would like to see fewer fossil fuels used.

The problem is what do you do with all the waste that's left over? Even the plant itself becomes radioactive, and only has a life span of about 50 years. It may produce less pollution while it's running, but the waste products can be just as bad in ecological terms as C02 emissions. And they'll be still be deadly for thousands of years after they've been disposed of. Plus there's a lot of security issues involved with the technology as well.

	17-05-2003 19:47									#177
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quote: Originally posted by Kropotkin There's nother thing I've noticed that I think more than americans have but I still haven't figured out what it's for. In the sink there seems to be some sort of grinder down in the hole. What's the point of that?

It's a garbage shredder. If you rip it up beforehand, it uses less space when it comes to time to haul it away. Or you can get the matter small enough that it just flushes down the drain. Not very many people have those anymore, they were only a fad for short awhile.

	17-05-2003 19:55									#178
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quote: What happens on the molecular level at the edge of a blade?

What do you mean? do you mean when a blade is used to cut something?

	17-05-2003 20:02									#179
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quote: Originally posted by Azazel actually, a dentist's job is very hard, and AFAIK, they're not MDs, they're are dental doctors, not medical doctors. I've paid for a root canal, that included a series of around 5 treatements ( in which I had a piece of my gum burned off, and a ceramic tooth carved out to replace my dead tooth) around 100$. The clinic is private and not government subsidized, the job lasted for a total of around 3 hours. Do you think that dental jobs are expensive here? I want to compare prices.

That's cheap! A root canal alone would probably run about $2-300 dollars, never mind the ceramic implant. I'm guessing here in Canada what you had done would probably cost close to $1000 CAN. At least that's what it cost me when I had a crown put on one of my teeth, which sounds to be about the same thing as what you had done.

	17-05-2003 20:20									#180
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quote: Originally posted by CyberGnu Urban: Sort of nitpicking: While the O-H bond is somewhat stronger than the C-H bond (about 20 kj stronger), it is significantly easier to break the O-H bond. This is because bond strengths doesn't tell you anything about the intermediates - if you have an ionic process, for example, you get completely different kinetics. Just compare tha acidity of water and methane. BTW, did I mention that coming up with better ways to break the C-H bond is what I do for a living?

Maybe you can answer my "I always wondered". In the long run, what will be the best way of supplying the hydrogen to our homes and vehicles if fuel cell technology becomes standard? Will the hydrogen be piped after it's been seperated, or will that be done in the home or refilling station by some device?