Final answer:
The rate at which a behavior occurs once it has begun in chemical reactions is known as the instantaneous rate.
Step-by-step explanation:
The rate at which a behavior occurs once it has begun is referred to as the instantaneous rate. This term is usually used in the context of chemical reactions to describe the rate of a reaction at a particular moment in time. In chemistry, this occurs during a period so short that the concentrations of reactants and products only change by a negligible amount. The initial rate is a specific type of instantaneous rate, referring to the rate of reaction at the very start when the product begins to form. Similarly, the average rate is computed from the concentrations at the beginning and end of a time interval, providing a mean value for the reaction's behavior over that period. An analogy to this would be a car's speed when it begins to slow down, with the initial rate analogous to the speed at the moment the brakes are first applied, and the instantaneous rate corresponding to the speed at any given moment thereafter.