Concentration is the number of molecules per volume, so a change in concentration will change the frequency of molecular collisions, which will change the rate of reaction. Surface area is the area of ​​a material exposed to another substance, so surface area affects the rate of reaction by determining how much of a substance can interact with other substances. Catalysts are substances that increase the rate of chemical reactions but are not chemically changed during the reaction. The problem in this lab is: “What factors influence the rate of chemical reactions?” The hypothesis is: “Temperature, concentration, surface area and catalysts influence the rate of the chemical