The " I always wondered" thread

[Az]

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.

[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?

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?

[Alinestra Covelia]

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.

[Urban Ranger]

Originally posted by Azazel

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?

[Urban Ranger]

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.

[Alinestra Covelia]

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?

[Ramo]

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.

[Eli]

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.

[Japher]

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.

[CyberGnu]

Urban:

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.

Nah, you overestimated me

Well, I can imagine worse things

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.

[CyberGnu]

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?

[CyberGnu]

(btw, assuming that the H(cation) is solvated in the above examples)

[Starchild]

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

[Traianvs]

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!

[Buck Birdseed]

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.