I'm not exactly sure whether this qualifies as quantum mechanics, but it has to do with how atoms work: suppose a glass plate falls and breaks (into two pieces, let's say, to keep things simple) on the floor. Is it possible to put it back together so that there is no longer a crack between the two pieces? Rule: you cannot melt the glass to remake the plate. I think it is not possible, but I am not sure why. Is it because the atoms at the edge of one piece of the glass no longer have the proper electron configurations to bond with the other piece? Basically, what does it mean to 'break', and why does 'breaking' not occur in liquids and gases?