Molecular rearrangement/construction - energy requirement

[LaCroix]

What energy would be needed to transform matter into a desired object?
I have been searching for some info about that throughout the net, but lacking a scientific education at that level, I can't find an answer to my question. I need it for a story that I am writing. Silly me wants to have it at least somewhat consistent with physics.

Just accept that someone is able to modify matter.
What minimum energy requirement would matter-reconstruction have?

I could imagine 3 different cases:

Reshaping an iron bar/wooden piece, stone. Molecules/Atoms just get shifted around. This shouldn't take too much energy, just slicing things apart, moving it and then bonding it together (flawless, of course, so the material would basically be equal or even improved at that seam)

Transforming something into a similar object, like an apple into an orange. It's carbon based, so it's basically a question of rearranging the atoms into new patterns(Apples and oranges are more or less just differrent combination of carbon and some other elements. So we rearrange at the atomar level or above. (The sugars, for example, wouldn't need to be reconstructed.) Should be quite hefty.

Transforming something into a different material, like wood into iron. You would have to split carbon atoms and use them to rebuild iron atoms, so we would reconstruct objects by modifying it at the sub-atomar level. Also, exess matter must be converted to air or something to vanish or surrounding air or other matter must be used to make up the difference, so the objects shape stais the same. I believe that this would take magnitudes more energy than the other 2 cases.

What energy requirements would someone face to do something like these things?

Given a tech base, they still could just convert matter to energy, and then use that energy (and some extra) to convert it back into the desired matter. That would mean converting 1 kg of water into 1 kg of iron would have no net energy difference, just the efficiency of the process would determine the energy requirement. (If they just convert more base matter and feed the process off it, it would need no other energy source.) Given the huge amounts of energy, that would seriously affect working object size, since that energy has to be stored somewhere througout the process.

Means that thing would only be viable for small object, since it releases roughly 20 MT energy per kg, and any percentage of that bleeding off into the environment would certainly cause problems.

Therefore, I would be interested if the process wouldn't be more efficient using other principles.

[LaCroix]

Not even an educated guess?

[Sky Captain]

If you can convert matter directly to energy then power requirements should be least of your problems.

To make one element into another you would need some sort of fusion nuclear reactor and some means to precisely control what elements you want to create and a way to quickly remove them from reactor before they got transmuted into another elements. IIRC you can fuse lighter elements till you get iron and generate power in process, but if you want to make elements heavier than iron you have to consume power to do this.

Easiest and more plausible solution is to have a device which you feed with necessary elements and which through complex chemical reactions creates the desired object. Energy requirements for this should`t be very high because it manipulates only chemical bonds leaving nucleus unchanged.

[Surlethe]

I don't think our current understanding of physics is able to give you an easy answer. It's possible in principle to calculate energy given a lattice of atoms, but very difficult in practice -- finding simple ways of calculating the functional is an open field of research.

[Steel]

If you want to know what it takes to convert one element into another then you want to look at nuclear binding energies. The energy required to convert one atom to another will be the difference in the binding energies. Note that binding energy is negative, you need to supply energy to break apart the nucleus of any stable atom. Iron has the lowest (most negative) binding energy per nucleon, hence fusion stops at iron, because at that point you dont gain energy from sticking nucleons together, and fission only works for things more massive than iron. You dont need to worry about electron binding energies if you're doing this sort of thing, as they are many orders of magnitude smaller (and thus we neglect all of chemistry -hurrah! ).

If you're going to the effort of changing one element into another, I think that energy difference is going to dominate the energy associated with the configuration of the matter in most cases. If you cant find anywhere that has calculated total binding energies of each nucleus, just use the (binding energy per nucleon)*(atomic mass) which will be close enough. So in order to get a rough estimate, just use conservation of energy.

Total energy of reactants + Energy difference needed = Energy products

calculate energy of products or reactants by taking binding energy per atom of each element*no of atoms of that element and adding it up for all elements.

You would need to supply the total binding energy of the reactants to get the thing going, then have your magic tech form it into the right products, but once you've got the thing going you only need to supply the energy difference to keep it going, as you'll get back a portion of your input once the products form.

[Fingolfin_Noldor]

If you want to know what it takes to convert one element into another then you want to look at nuclear binding energies. The energy required to convert one atom to another will be the difference in the binding energies. Note that binding energy is negative, you need to supply energy to break apart the nucleus of any stable atom. Iron has the lowest (most negative) binding energy per nucleon, hence fusion stops at iron, because at that point you dont gain energy from sticking nucleons together, and fission only works for things more massive than iron. You dont need to worry about electron binding energies if you're doing this sort of thing, as they are many orders of magnitude smaller (and thus we neglect all of chemistry -hurrah! ).

Well, technically speaking, and to be more precise, you do get heavier elements past iron from fusion, but only at the point of supernova. Of course, the energies in question are quite large.

[Darth Wong]

I could imagine 3 different cases:

Reshaping an iron bar/wooden piece, stone. Molecules/Atoms just get shifted around. This shouldn't take too much energy, just slicing things apart, moving it and then bonding it together (flawless, of course, so the material would basically be equal or even improved at that seam)

Actually, it takes a lot of energy. Chemically bonded atoms have a chemical binding energy, just as the subatomic particles in an atomic nucleus have nuclear binding energy. The amount of energy is much lower per atom of course, but it is still significant. In order to "shift around" those molecules and atoms, you need to break chemical bonds, which means you need to overcome the chemical binding energy. That's why metal heats up as you deform it. In fact, in a steel rolling mill, pieces of steel actually get red-hot as they pass through successive series of rollers, and all the rollers do is flatten them out.

The amount of energy required is related to the hardness of the object, which is in turn related to the microstructure and strength of chemical bonds.

Transforming something into a similar object, like an apple into an orange. It's carbon based, so it's basically a question of rearranging the atoms into new patterns(Apples and oranges are more or less just differrent combination of carbon and some other elements. So we rearrange at the atomar level or above. (The sugars, for example, wouldn't need to be reconstructed.) Should be quite hefty.

Not necessarily any higher than your previous example, although it would obviously require technology which we don't have. You're still talking about breaking chemical bonds and moving material around.

Transforming something into a different material, like wood into iron. You would have to split carbon atoms and use them to rebuild iron atoms, so we would reconstruct objects by modifying it at the sub-atomar level. Also, exess matter must be converted to air or something to vanish or surrounding air or other matter must be used to make up the difference, so the objects shape stais the same. I believe that this would take magnitudes more energy than the other 2 cases.

Obviously, subatomic reconfiguration would require far more energy, because nuclear binding energy is far larger per atom than chemical binding energy.

[LaCroix]

Thank you for your help.

Ok, just so I got it right:

The chemical bond keeps molecules together

The nuclear bond keeps atoms together, with a energy of 7.5-9 MeV per nucleon(and some smaller elements with much weaker bonds). This bond has to be overcome to split the atom. Rejoining the atom will need to overcome the electromagnetic force, which grows faster then the strong nuclear force, thus making it harder to join bigger atoms.

So, fission of lighter elements up to iron produces energy(thus making iron the end product for fission), and from Iron on, it needs energy. (So transforming lead to gold would produce energy? Sweet - an alchemist's dream! Maybe that's why gold is so worthless in the federation, you could replicate it from iron and gain energy in the process. )

That would mean that carbon(=wood)-> iron produces energy, while iron->carbon needs energy. Funny, common sense would make you think it's the other way round. So much to common sense.

Would that electromagnetic force problem for bigger atoms mean that such a product might be unstable, and decay again? Or just add (lots of? )energy to the binding process cost?

Just to see if I got the process/numbers right.

1 Joule is 6.2415 ×10*18 eV
1 mol is 6.022x10*23 Nuclei

Depending of the element, you face a binding energy of between approx. 720 and 870 GJ per mol.
That would dissolve it to plasma, starting the process.

Recombining that to a different element would produce or need energy, according to the binding energy of the target element.

Of cause, the mass of the target element object is the same, causing a volume change. To offset that, if wanted, you would need additional energy to convert to matter, or get some additional matter from somewhere to convert and add. Transforming to a smaller element, you would gain excess matter to do whatever you want (store, annihilate).

Creation of 1 mol of iron (55.845g·mol−1) by m/e conversion from carbon would need ~20 PJ energy (assuming an 50% efficiency in conversion - times two = 25% overall) in any direction.

Dissolving ~5 mol carbon(7.5MeV - > 5x720GJ spent) and reforming 1 mol iron (8.5MeV -> ~800GJ gained) would mean spending 6.8 TJ (again at 50% efficiency per conversion), and reversing it would gain 200GJ

So creating it by m/e conversion would need 3000 times more energy than making it from an existing plasma, given the same efficiency?

Chemical binding energy would be how much smaller than nuclear? 3 orders again?

I'm apologizing in advance if my math is making you weep.

[Admiral Valdemar]

I'd look up that superlaser in Scotland named VULCAN which is a testbed for transmuting energetic and dangerous radioistopes into safer, more stable ones.

[Surlethe]

The nuclear bond keeps atoms together, with a energy of 7.5-9 MeV per nucleon(and some smaller elements with much weaker bonds). This bond has to be overcome to split the atom. Rejoining the atom will need to overcome the electromagnetic force, which grows faster then the strong nuclear force, thus making it harder to join bigger atoms.

Pretty much correct.

So, fission of lighter elements up to iron produces energy(thus making iron the end product for fission), and from Iron on, it needs energy. (So transforming lead to gold would produce energy? Sweet - an alchemist's dream! Maybe that's why gold is so worthless in the federation, you could replicate it from iron and gain energy in the process. )

Backwards. Fusion of lighter elements produces energy, while fusion of heavier elements soaks up energy. Fission of lighter elements requires energy, while fission of heavier elements releases it.

Edit: this image shows nuclear binding energies.

That would mean that carbon(=wood)-> iron produces energy, while iron->carbon needs energy. Funny, common sense would make you think it's the other way round. So much to common sense.

Actually, your common sense was right.

Would that electromagnetic force problem for bigger atoms mean that such a product might be unstable, and decay again? Or just add (lots of? )energy to the binding process cost?

Well, that's one motivator of nuclear decay: the heavier an element, the greater the coulomb repulsion and the more likely it is to decay.

[Gil Hamilton]

Transforming something into a similar object, like an apple into an orange. It's carbon based, so it's basically a question of rearranging the atoms into new patterns(Apples and oranges are more or less just differrent combination of carbon and some other elements. So we rearrange at the atomar level or above. (The sugars, for example, wouldn't need to be reconstructed.) Should be quite hefty.

Some notes:

It's not simply a matter of energy and rearranging things. Some things are fiendishly difficult to do but necessary for what you are talking about. It's NOT easy to make a new carbon-carbon bond, for example, and you can see it in biochemistry that nature goes to great lengths not to break them in the body unless they absolutely have to (some metabolic pathways are pretty convoluted because of this, look up some of the ways the body works with sugars). That's why an Organic Chemistry joke exists: "I'm going to be an organic chemist because I want to be rich. I'll just make a new way to form a carbon-carbon bond in a test tube, publish the paper, and order a plane ticket to Europe to go collect my Nobel Prize". The sort of transmutation you want to do is necessarily going to involve some pretty damn convoluted pathways to make what you want.

For example, an orange has more citric acid than an apple, so you are going to have to make some more, which is actually doable from glucose, but the way its done naturally in the cell involves 10 proteins to from glucose to a pair of pyruvates by itself via glycolysis, then several more hops from glycolysis through to the Citric cycle to arrive at citric acid. You could probably conceive a chemical pathway to do it more efficiently (though glycolysis and the citric acid cycle have been around for damn near forever in terrestrial life, so it's pretty damn hard to improve on), but you are going to have to go through some process of cleaving this bond and redox here and protecting functional groups there and this and that to take what you have and produce what you need in significant yields. Organic chemists take YEARS studying one chemical synthesis and whole grad school careers can be from start to thesis based on such things.

At a certain point, even if you ignore the nuclear stuff which other people are more qualified to answer than I am, even turning an apple into an orange, which is reasonably close to being made of similar materials, starts earnestly looking like Magic Pixie Wand stuff. You can make a gross estimate of the energy requirements for making and breaking X mols of various bonds and such in order to achieve it (you can find tables with the energy of a mol of various atomic bonds, which basic ones are available in the appendices of any Physical Chemistry textbook), but if your goal is chucking an apple into one end of a machine, letting it go "DING!" and having an orange fall out, you've left the realm where its meaningful to make such estimates because the mechanism is completely unknown.

If you are writing this for a story, I'd recommend making up a number. Remember, you are using some unknown future moonbat technology. In a perfectly efficient world, severing a bond in one place and making the exact same bond somewhere else costs NO NET ENERGY, because you get the energy from breaking the bond back when you make a new one. Without a mechanism or process, you can kind of handwave the energy requirements some and let suspension of disbelief take over, as long as you are careful and don't write anything obviously stupid (sort of like how science fiction writers treat FTL travel). Your general assembler works, it goes DING!, and you can turn grass into steaks without the intermediate cow, requiring some amount of power. Congratuations, it's science fiction.

[LaCroix]

Thank you Surlethe.
(And thanks to my PC for crashing twice while replying, too.)

I got it right, I just always confuse the words fusion and fission.

So the columb repulsion is what prevents making uranium by refusioning the fission products, and causes energy gain although the fission products have higher nuclar binding energies, right?

[LaCroix]

...lots of helpful stuff...

Thanks, that's exactly why I originally thought it would be a lot more complex than just changing shape. (a bar of metal into a plate or whatever)

Once you get organic, there is rather complex stuff in there, and you have to keep what you need, add and remove from some Proteins, acid and stuff, and then reorganiza all that into a certain pattern.

I basically just wanted to get some energy estimates (and I try to be resonable in efficiency, therefore my standard 50% rate), so I can define some upper and lower limits for that handwavium, you know minimal energy to overcome bonding, how fast would it be with how much energy, will it be easier to do stuff in one direction or the other, that stuff.

The better I define those limits up front, the less 'voyagerism' creeps into my story.

[Gil Hamilton]

You don't need to get into "Voyager-ism" to have crazy technology. The difference between super advanced "magic" technology and technobabble is how you present it, not whether its remotely technically feasible. A character having a 2000W EnergyStar(TM) Replicator from Whirlpool is something that no one would think twice about, regardless of of the fact that 2000 watts of power probably isn't going to cause a pile of organic material to jump up and become a hamburger... at least not in time for dinner at any rate.

I'd suggest thinking thermodynamically, rather than worrying about making and breaking mols of bonds. What are you making into what? Some processes are more costly than others. For example, take trinitrotoluene (good ole TNT). It's EASY to turn that into thermodynamic product, you don't need a replicator for that, just a spark, and you'll get CO2, N2, O2, and H20. In terms of energy, it's "downhill" you could say.

But what happens if you want to take CO2, N2, O2, and H20 and turn it back into TNT? The materials are freely available, you just feed air into your replicator. Now, you are going thermodynamically "uphill". In fact, you are going to be putting at minimum the same amount of energy as that TNT explosion, since you are stuffing all that energy BACK into a high energy molecule.

So think about what you are trying to achieve and what building blocks you have.

---With sufficient handwavium, you can easily get away with saying that turning an apple into an orange doesn't require that much energy to do (though turning an apple into another fleshy fruit, like a pear, would be easier). You'll be going uphill thermodynamically sometimes and downhill others and most of your actual energy will be lost in the process and to entropy.

---Turning grass into steak without the intermediate cow is going to be harder, since grass is pretty much all cellulose (carbohydrates) and steak is protein and fat. You are going to have to do some real molecular fidgeting around to turn cellulose into protein and fat*. This is almost certainly be a higher energy process than turning an apple into an orange.

*Fat less so than proteins. In the case of fats, everything is present in carbohydrates to make fats, and in fact the body does it by breaking carbs down into two carbon acetates and assembles them into fatty acids. Proteins are going to be higher energy, because you are going to have to get nitrogen in the mix somewhere and getting it from N2 gas is going to be energy EXPENSIVE due to the fact that diatomic nitrogen gas is triple bonded.

---Turning available gases into an apple, orange, or steak. You are going majorly uphill thermodynamically. All chemical paths are up the energy curve and you are paying for every bit of it. This is going to be a high energy process. In fact, nitrogen specifically, which is necessary for alot of things you are going to want to replicate, is going to cost you a ton by itself for the reason listed about. Nitrogen fixing, which is very useful industrial and biology, involves breaking that triple bond, which according to my P-chem book requires 941 kJ/mol. Aside from some rather industrious microbes, you can see why organisms don't like doing it and why it's a pain in the ass for industry. While other molecules have a smaller cost of admission, any replicator that turns gas into anything is going to necessarily be expensive.

---Going the other way. Turning complex molecules into smaller molecules. This can probably be done fairly easily, though keep in mind you aren't necessarily going downhill depending on the pathway. Hell, depending on how simple (like gases), it's just plain combustion. It probably wouldn't be that energy intensive to feed food stuff, for example, into your replicator and have it squirt out chemical reagents of the same elemental composition. In fact, it would organic chemists wet dream if you could handwave past all the horrible chemical synthesis to arrive at the molecule you want at a high yield.

Those are the sorts of rules of thumb I'd suggest.