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What happends when you cut something in half?

by epislon58
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epislon58
#1
Aug19-13, 06:56 PM
P: 49
What happends to atoms when you cut something in half, say a sheet of paper. In a solid, atoms are packed tightly, so I was curious and wondering of this is even a valid question.
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ZombieFeynman
#2
Aug19-13, 07:39 PM
PF Gold
P: 278
Bonds (electromagnetic interaction between outer shell electrons) between atoms break.
'roidbreaker
#3
Aug19-13, 11:25 PM
P: 14
Quote Quote by ZombieFeynman View Post
Bonds (electromagnetic interaction between outer shell electrons) between atoms break.
I doubt cutting a piece of paper in half is chemistry.

Quote Quote by epislon58 View Post
What happends to atoms when you cut something in half, say a sheet of paper. In a solid, atoms are packed tightly, so I was curious and wondering of this is even a valid question.
nevermind. you're breaking and untangling these:

http://en.wikipedia.org/wiki/Glycosidic_bond

ZombieFeynman
#4
Aug20-13, 09:54 PM
PF Gold
P: 278
What happends when you cut something in half?

Quote Quote by 'roidbreaker View Post
I doubt cutting a piece of paper in half is chemistry.



nevermind. you're breaking and untangling these:

http://en.wikipedia.org/wiki/Glycosidic_bond
You can reason this out without having to consider fancifully named bonds on some wiki page. There are four fundamental forces. Gravity is far too weak to hold any small object like paper together. The purpose of the weak nuclear force is to mainly mediate certain radioactive decay. It is also too weak to hold paper together. The strong nuclear force is too short ranged. Weve found the culprit! Electromagnetism! Now it is easy to convince yourself that paper is held together by bonds between atoms just like most solids. If the paper comes apart then, it must be because these bonds break.
Baluncore
#5
Aug20-13, 11:16 PM
Sci Advisor
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P: 1,761
Paper is a sheet of cellulose fibres. Each cellulose molecule is a long polymerised chain of sugars. When you cut paper you tear apart the bonds between adjacent sugars and expose the broken bonds on both sides of the tear to the environment. It is highly probable that some available reactive chemical, such as water, will satisfy the available bonds and so prevent the polymer chains joining up again.

The energy you need to tear a material can be calculated from the bond strength in the polymer and the density of the fibres. So when you cut or tear a material you are performing chemistry. You are using energy to break chemical bonds and then allowing them to react again with their environment.

This subject straddles the twilight zone between Physics, Chemistry and Engineering.
Your particular view will be determined by your viewpoint.
'roidbreaker
#6
Aug22-13, 08:49 PM
P: 14
Quote Quote by ZombieFeynman View Post
Electromagnetism! Now it is easy to convince yourself that paper is held together by bonds between atoms just like most solids. If the paper comes apart then, it must be because these bonds break.
These bonds could be intertwined carbohydrate chains that get untangled, no? Yes, electromagnetic potential, but it doesn't necessarily have to be broken. Does it?
Baluncore
#7
Aug22-13, 09:43 PM
Sci Advisor
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P: 1,761
It takes energy and intelligence to untangle chains.

When two chains lie against each other, some cross bonds form between the chains. It takes only a few of these cross links to exceed the strength of one chain. If there were no bonds between the chains then there would be no friction and the chains would simply slide apart.

A bond can be seen as an attraction to a situation of local minimum energy. To escape that attraction energy must be provided. That breaks the interrelationship and therefore the bond.


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