Of course, contact with another molecule does not yet necessarily trigger a chemical reaction between the two.
Indeed, spatial and temporal organization is a fundamental property of living systems and of great interest for chemical reaction systems in general.
Other processes such as chemical reaction and heat or mass transfer have similar dependencies on the residence time distribution.
If a fast chemical reaction occurs, the mixing efficiency can be inferred from the formation of product.
In the case of propagating reaction fronts the exothermic chemical reaction plays the role of heating from below.
The presence of water in excess of that required for chemical reaction creates minute voids, which propagate crazing and create visual defects.
The difference between the curves is the energy from the chemical reaction.
The change of chemical reactions from in vitro into the biochemical reactions in vivo means that a separate chemical reaction loses its 'spontaneous' status.