How does cutting through material work on an atomic scale?

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pedicabdriver

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Nov 29, 2007
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I understand the whole concept of pressure being focused on a very small area on a small scale, but how does cutting through stuff happen on a molecular level? Are the bonds between atoms being broken? My head hurts thinking about it. :confused:
 
No, you're not splitting atoms with your blade,

...but you might be parting a few molecules.




Big Mike
 
After I get done sharpening my knives, you can see the material parting like the Red Sea when the knife gets anywhere near the material. :eek:

Well I wish.

Bill
 
Strong intramolecular chemical bonds (i.e. covalent, bonding between atoms) won't be broken, but you are breaking weaker intermolecular bonds (i.e. Van der Waals/London Dispersion) by concentrating force over a very small area (Pressure = Force/Area). The force you apply via the knife overcomes the forces holding molecules in the structure together.
 
Yeah, unless you cut one thing and end up with something else, you are not breaking molecules.

It is not too difficult to comprehend. You are separating material...just like if you tear a sheet of paper, except a cut is a more directed/controlled separation.
 
In one respect it is seemingly not difficult to comprehend.

In another respect, it is almost impossible to comprehend, as contemporary science does even begin to understand the things which we are attempting to describe. We don't even know what an electron is, for example. We say that it is a subatomic partical with negative charge which exhibits properties of both a particle and a wave, but that is woefully short of actually understanding it.

JMO. :thumbup:
 
pedicabdriver said:
I understand the whole concept of pressure being focused on a very small area on a small scale, but how does cutting through stuff happen on a molecular level? Are the bonds between atoms being broken? My head hurts thinking about it. :confused:
Click to expand...

When you cut something with a knife, you are technically pushing apart large clusters of molecules that are stuck together via electromagnetism.

The electromagnetic force is what keeps electrons bonded to atomic shells, and it is also what produces the ionic and covalent bonds that hold large structures of molecules together. Remember, atoms and molecules consist mostly of empty space - the solidity we feel is actually the forces their shells produces. A sharp knife basically has an edge small enough such that its own magnetic forces fit snugly in between those of the object it is "cutting". So really, knives are like very fine pry bars.
 
You really have to be careful if your knife is too sharp. You can split an atom and vaporize your whole house.
 
This made me remember:
In the interesting "His Dark Materials" trilogy of young adult novels (well, the first book is awesome and it goes downhill from there), a boy has a weird knife that allows him to cut his way towards alternate realities.
 
I just hate it when I'm cutting stuff and all those halved and quartered atoms have to be swept up afterwards.
 
Alberta Ed said:
I just hate it when I'm cutting stuff and all those halved and quartered atoms have to be swept up afterwards.
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I do not like to cut all the way through 'em. I prefer to carve out a neutron or two and create isotopes. It takes a steady hand...
 
Dagon said:
This made me remember:
In the interesting "His Dark Materials" trilogy of young adult novels (well, the first book is awesome and it goes downhill from there), a boy has a weird knife that allows him to cut his way towards alternate realities.
Click to expand...

I've cut myself with my knives on occasion, which definitely made me FEEL like I'd entered an alternate reality... :eek:
 
For one, it is unlikely to cut molecules with a knife, may be superlong organic ones. I've read an article back how certain long molecules are being broke down into less useful stuff for consumption in the finely processed food. Although, I take that with a grain of salt.

Second, if you are cutting pure material, as in from the periodic table, then you are breaking bonds between atoms, e.g. cutting aluminum sheet.

Splitting atoms releases enormous amounts of energy, and nuclear(not thermonuclear), or fission bomb is just that, atoms being split.
 
Gator97 said:
For one, it is unlikely to cut molecules with a knife, may be superlong organic ones. I've read an article back how certain long molecules are being broke down into less useful stuff for consumption in the finely processed food. Although, I take that with a grain of salt.

Second, if you are cutting pure material, as in from the periodic table, then you are breaking bonds between atoms, e.g. cutting aluminum sheet.

Splitting atoms releases enormous amounts of energy, and nuclear(not thermonuclear), or fission bomb is just that, atoms being split.
Click to expand...

That would explain all those tiny mushroom clouds.;)
 
Imagine one of those indoor parks that kids play in. Specifically, think of the small pool filled with small plastic balls.

At the molecular level things behave "kind of" (emphasis on "kind of") like this. The balls settle into a regular shape and volume due to gravity. The same with molecules and atoms--they are always moving toward a "position" of stability.

Now, imagine coating those play balls with something sticky--maybe honey or molasses. This would act somewhat like the inter-molecular forces that keep molecules together.

A giant wedge made up of similar play balls, but held together with superglue, is pushed into the pool of play balls. The balls held together by honey slide apart, pushed out of the way by the "harder" superglued wedge of balls.

This is something like what cutting at the molecular level would be like.
 
Cynic2701 said:
Imagine one of those indoor parks that kids play in. Specifically, think of the small pool filled with small plastic balls.

At the molecular level things behave "kind of" (emphasis on "kind of") like this. The balls settle into a regular shape and volume due to gravity. The same with molecules and atoms--they are always moving toward a "position" of stability.

Now, imagine coating those play balls with something sticky--maybe honey or molasses. This would act somewhat like the inter-molecular forces that keep molecules together.

A giant wedge made up of similar play balls, but held together with superglue, is pushed into the pool of play balls. The balls held together by honey slide apart, pushed out of the way by the "harder" superglued wedge of balls.

This is something like what cutting at the molecular level would be like.
Click to expand...

:thumbup: I'll go with that one.
 
Good analogy :thumbup:

Just as metallic bonding > intermolecular forces in this case, materials like diamond, with its covalent crystal structure, are still harder.
 
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