Is energy required to form bonds [phase change]

Question

My question is if any energy is required to form bonds, for instance when there is a phase change?

If I am correct, energy might be required in the beginning, to make the reaction start and then release a bigger amount of energy than it was putted in. However, in terms of molecular behaviour in a phase change, I think there should not be any energy required to make the molecules to form bonds, if they are placed in a system which has a lower temperature than the molecules. Would they not lose the kinetic energy after a specific time?

Answer 1

Bond formation always lowers the energy of the system (or bond formation is a consequence of lower energy, take your pick.)

Indeed, you may have to add energy, because presumably certain bonds must break in order to rearrange the atoms.

Adding energy won't guarantee formation of much higher energy isomers, because the atoms have a large amount of kinetic energy, and so they can just as easily turn around and go back whence they came.

Sometimes the kinetic energy can be dissipated by solvent, collisions with inert gasses, etc. and then you may end up with a measurable quantity of the higher energy species.