The document discusses the rate of reaction and how to measure it. It defines rate of reaction as the speed at which reactants are converted to products. There are two ways to measure rate of reaction: (1) average rate of reaction, which is the average value over a period of time, and (2) rate of reaction at a given time, which is the actual instantaneous rate calculated from the slope of a graph at that point in time. Observable changes in factors like gas volume, precipitate formation, color change, or temperature can be used to determine the rate of reaction.