What determines the temperature of an object at the molecular level?

At the molecular level, temperature is related to the random motions of the particles (atoms and molecules) in matter. Because there are different types of motion, the particles' kinetic energy (energy of motion) can take different forms, and each form contributes to the total kinetic energy of the particles.

The Original equation for this reaction is:
CO + O2 → CO2
this is not a balanced equation.
as the reactants C = 1 and O= 3
and the products C= 1 and O=2
so we put 1/2 O2 instead of O2 to balance the no. of O atom on
 each side.
CO + 1/2 O2 → CO2 to get the integers number we will multiply by 2 
the final balanced equation is:
2CO(g) +O2(g) → 2CO2(g)
So we finally have 
at the reactants side C atom = 2 & O= 4
at the products side C atom = 2 & O = 4