[reed]

How exactly does one object break and separate another object into separate pieces? How does a knife cut through wood? To put it simply: I understand the intermolecular forces involved that keeps matter together, so I am assuming that the atoms of the knife can pass through and separate the intermolecular forces of the wood. However, the intermolecular forces in a solid crystalline structure are much more powerful than those in a liquid, so once something is broken or fractured, why isn't the fracture mended through the intermolecular attraction?

Thanks!

[enahs]

q[However, the intermolecular forces in a solid crystalline structure are much more powerful than those in a liquid, so once something is broken or fractured, why isn't the fracture mended through the intermolecular attraction?]q

I guess you are asking, if the intermolecular forces between ionic structures are so strong, then how come once you break a crystal apart why can you not just hold them together and they reform?

If that is the case, first. It is a common misconception that Ionic bonds are the strongest bonds. Ionic and covalent bonds are typically on the same order of strength. In short and simplified, covalent bonds are directional where ionic bonds are unidirectional, and so the crystal lattice as a whole is strong, but the individual bonds are not all that stronger then a covalent bond.

Why will they not go back together? Well, a few reasons.
Yes there are very strong attractive forces between ionic bonds, but there are also very strong repulsive forces from like ions. This is how crystal cleavage works, and is so spectacular; you physicaly move the atoms enough and displace them from the lattice so the repulsive forces in a small area is more then the attractive forces. Crystal lattice are also imperfect. So if it were possible to stick them back together, you would have to physically be able to do it with atom dimension precision.
The other main reason is surface chemistry. Surface chemistry is very complicated and sometimes radically different then the chemistry of the internal structure of which people typically learn about.