Breaking of a Single Bond

Use the model below to explore the following questions:

1. This is considered to be an endothermic reaction. Why?
2. Set up the model so that you have a strong bond in the A₂ molecule but no reaction happens. (Hint: you can adjust the starting temperature - or kinetic energy - of the reactants.) Describe how you did it.
3. Do the same thing, but use a weak bond for the A₂ molecule.
4. Why doesn't this reaction work all of the time when the previous reaction: A + A --> A₂ always worked despite the initial kinetic energy of the reactants?