The question seems simple. Since atoms make up molecules, molecules can be changed back into atoms. But what is the most difficult thing to do is change molecules into more massive atoms. Could a water molecule be changed into a fluorine atom? The3 answer is yes. But it is rather difficult and to my knowledge hasn't been done yet.
For one thing, there isn't a demand for water molecules to be changed into fluorine. One way to do it could be by creating a plasma of the molecule and blend the atomic particles to form the heavier atom. With hyperlight physics, the disassembling of the molecule and the re-combing of the particles to create fluorine would be done so fast that there shouldn't be an atomic explosion as energy is released in the fusion reaction. Also, another particle or two may be needed to be added to the re-combing particles that are fused when the two hydrogen atoms are merged with the oxygen atom.
The covalent bonds that keep two atoms of hydrogen attached to an atom of oxygen are weak enough to be broken by chemical means. But fusing them into a heavier atom requires an atomic reaction. Another neutron would be needed to form fluorine since hydrogen doesn't have a neutron in its nucleus. To make the atom stable instead of creating an isotope of oxygen, a hyperlight speed reaction would be required to blend the particles and produce a stable atom. The number of steps required to go from water to fluorine are too many to do the reaction in a split second. But hyperlight-speed reactions are fast enough to do the trick.
Hyperlight reactions often decouple particles to allow like particles to repel off of other like particles and eventually produce a hyperlight-speed energy mass. This may be how repulsion-drive engines will work. Instead of matter/anti-matter reactions, accelerated particles with like charges facing out from energy mass bundles will push crafts beyond the speed of light. Such hyperaccelerated energy mass bundles may be required to disassemble the water molecules, insert the neutrons, and recombine the particles into fluorine. Excess energy would be removed by absorption by the hyperaccelerated energy mass. The energy mass would be strong enough to prevent the particles from flying apart in an explosion.
Long molecules like DNA would be disassembled and multiple atoms would be produced. There may be a limit to the size of atoms. But for simple molecules, hyperlight speed disassembling and reassembling should do the trick. Changing water into gold or platinum could even be done as long as many water molecules are used. But it may be cost-prohibitive to do it. But if it can be done, turning lead into gold or platinum will prove to be much easier and less expensive. Particle removal from lead is needed to form gold and platinum.
Iron-oxide (rust) could be fused into gallium or germanium. But there would be an atomic explosion that will need to be controlled. But this should be done fairly easily in a hyperlight-speed reaction. If energy is released, it might be used to produce another plasma that will run steam generators. That means people could throw in rusty items and out would come a strategic material for electronics. That means if a company needs a certain material, hyperlight-speed fusion may be used to supply the company with what is needed. It just may prove to be too expensive to be practical. But it could be done.