how come if you put two exactly the same solids next to each other they won’t bond?

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Like if you had a gold bar and placed them next to each other. They’re the same atom? I have a basic understanding in chem but still so much confused me

In: 4

The contact areas contain impurities, such as oxides, grease or moisture. There are air pockets inbetween microscopic features on the surface. Clean, polished metals actually do join together in the vacuum of space.

So under the proper conditions they do! It’s called vacuum welding, or space welding. Two identical metals with no oxide layer brought together in a vacuum will spontaneously fuse together. It’s super cool!

If you took two random objects and pressed them together, they would look a lot like taking two chunks of mountainous land and pressing them together. There’s almost no contact area between them; they only touch at a couple of the mountaintops and nowhere else.

This is what ‘flat’ surfaces look like on the microscopic level. If we carefully flatten and polish a material, it *will* actually stick, but even our best polishing techniques are far from perfect.