Final answer:
In chemistry, the rate at which units arrive at a process, commonly known as the reaction rate, refers to the change in concentration of reactants or products over a period of time, similar to people arriving at a taxi stand or a runner's speed in a race.
Step-by-step explanation:
The rate at which units arrive at a process, such as in chemical reactions, is an important concept in chemistry. This rate, also known as the reaction rate, refers to the change in concentration of a reactant or product over time. To understand this, consider chemical reaction rate examples where some reactions happen almost instantaneously, while others take longer.
The arrival frequency of reactants can be thought of as people arriving at a taxi stand, and the taxis represent enzyme molecules in an enzymatic reaction analogy. If more taxis (enzymes) are available and not saturated, increasing the number of people (substrate concentration) would increase the rate at which they are taken to their destination (converted into product).
In another example, if a runner takes 11 seconds to run a 100-meter dash, his rate is 9.09 meters per second, illustrating how rates are typically expressed as a quantity per unit of time. In chemistry, instead of physical distance and time, we talk about changes in concentration over time. The rate-determining step is akin to the smallest funnel in a series dictating how fast a container fills, representing the slowest intermediate process controlling the overall rate of a reaction.