The type of catalyst and its temperature will be changed in a. How: Measure the volume of hydrogen peroxide using a precise measuring cylinder or pipette before every trial. b. Why: Ensuring the same volume is used in each trial maintains consistency in the reaction conditions. 3. Amount of Catalyst: a. How: Weigh the same mass of each catalyst using an analytical balance for each trial. b. Why: Different amounts of catalyst can lead to different reaction rates. Keeping the amount constant ensures comparability and ensures accuracy and precision of intended reactions. 4. pH of the Catalysts: a. How: Measure and adjust the pH using a pH meter and buffer solutions. b. Why: Catalysts can be sensitive to pH changes, which can affect their activity and the reaction rate.