Question

what causes the collision and vibration of atom and molecules

Answer 1

It can, albeit crudely, be explained by the equipartition theorem of classical statistical mechanics:

"the AVERAGE KINETIC ENERGY of molecules comprising a bulk body is proportional to the TEMPERATURE"

(i.e. the larger the temperature in the room, the larger the average kinetic energy of molecules in the room.) The molecules are free to distribute this energy amongst its various internal and external MODES OF MOTION. The internal modes include molecular rotation about the molecular centre of mass, vibrations and electronic transitions. The details of this distribution (i.e. 'how much energy each mode gets') depends on the quantum mechanical description of the molecules in question which may include some quite complex coupling between the modes (i.e. their dynamics will be inextricably linked).

I hope this has helped! (:

Answer 2

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Answer 3

Why ~.~? :p