If I cut a thing in two, are the two pieces together exactly the same size as the original?
Or to rephrase it: does a knife/scissors/etc just split something or does it remove something?
Are you talking molecular level? Then yes, some is lost. If you’re talking human noticeable levels, it depends on the material and cutting method.
I’m pretty sure that generally some particles break off from either side whenever you cut something in half. When I cut paper with scissors I get a distinct smell, that’s clearly paper particles that have escaped into the air. Under the right conditions you may even see some dust.
When using a saw it is very explicitly removing material to create a gap between the two sides. You can see this clearly in a lot of woodworking videos on YouTube. For other tools like a knife, it’s not as obvious, but I still think some material will inevitably be lost no matter what you do.
Maybe some extremely specialized nano-scale methods can cut things without losing material, but I doubt that’s something you can do on an everyday life scale.
Disclaimer: I’m not an expert and I did 0 research, just giving my opinion and personal knowledge (which may be wrong).
You can smell cut paper? 🫨
I think so, but if I’m honest, there’s a chance I’m just imagining it 😅
Really depends on the kind of paper. Used to habe to do technical drawings, and there is indeed a distinct smell to certain kinds of paper, but not your usual copy-grade sheets.
This is pretty much what I was going to say. You always lose material, but the amount lost varies drastically based on the method. Even when using a knife or shears in a purely straight motion (no sawing or sliding), the material has to deform to make room for the cutting device. It may rip apart, it may bulge into itself, it may crumble, it may do it all. Try cutting a thin slice off a nice block of cheese and you’ll see nearly all the deformation go to the slice, while the knife will be coated in cheese
+1
The term for the material removed to make a cut is kerf. You hear about it a lot with woodworking as not taking into account can lead to inaccuracies in the final dimensions of your materials.
I would think separating a material by passing another through it is cutting while separating materials with only force would be breaking if it happens along a length or tearing of it happens gradually from a single point.
A knife generally tears, it separates the material in front, causing it to tear ahead of the blade.
The CNC (computer controlled cutters) metals that slide into each other so tightly that you cannot see the seam, are created using 2 separate blocks of metal, one becomes the outer block and the other becomes the inner block, then they’re both polished together to appear seamless. There’s no practical way (as far as I know) to make significant cuts without losing or malforming some of the material (you can cut playdough without losing any of the mass, but it’s bunched up along the cut path.
My very old understanding of how materials behave
It will remove some amount of material when you cut.
If it is enough for anyone to care about is another question.
Or was the question what happens on a molecular level and if cutting is any different than sawing at that level?
If you shear (scissors) then there should be less loss, maybe some distortion though. If you saw, you lose the sawdust. if you slice (knife), it might be either way or a bit of both.
Most likely you lose something, whether it’s a loss that matters, that depends.
Or to rephrase it: does a knife/scissors/etc just split something or does it remove something?
So, solids aren’t really solid. Like, at an atomic level no two molecules are actually touching. Think of it like a magnet floating above another.
What you cut it with matters too, something insanely sharp like a medical grade obsidian blade wieled with skill is so sharp, it’s just going to separate the molecules. And remove very little material.
Try to cut a piece of paper in half with a baseball bat, and lot of material won’t be attached to either of the two biggest pieces. Because it’s a big blunt object.
But also, because some of the bonds between atoms/molecules were broken, some of the energy was lost. And energy is mass, so you can lose mass even if all the particles are still on either piece.
atoms/molecules
Two completely different things, on a molecular level that could just be stored potential energy. Like when a mousetrap is set or not, it doesn’t change it’s weight.
That’s how splitting atoms make atomic bombs there’s potential energy holding shit together, and we poke one to make it release which cause a giant chain reaction which adds up. Even then the “lost” mass is just blown up. I don’t think used my lease fuel gets substantially lighter for example.
Not bonds within atoms, bonds between atoms. Or molecules. That depends on the exact material being cut.
And yeah, on a large scale it gets exploded, but on a scale of cutting paper with scissors it mostly gets lost as heat.
I believe, chemically, molecules with a stronger bond push molecules with a weaker bond apart. And physically, the applied force over the affected area decides the amount and direction of the bonds being separated.
In most cases cutting causes a physical change not a chemical change.
I believe when they say chemically they are referencing, “at a molecular level”
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