In this model, two atoms can form a bond to make a molecule. Experiment with changing the concentration of the atoms in order to see how this affects the reaction rate (the speed at which the reaction occurs). Follow these steps: 1. Add some atoms. (You can add atoms by pressing the buttons multiple times). 2. Run the model. 3. Reset the model and try a different concentration. Gauge the reaction rate by using the graph to see when the reaction reaches 80% completion.