Define reaction rate and identify the independent and controlled variables in the provided experiment.

Here are the solutions to your questions:

12.1
The reaction rate is the speed at which a chemical reaction proceeds, defined as the change in concentration of a reactant or product per unit time. It indicates how quickly reactants are consumed and products are formed.

12.2

• 12.2.1 Independent variable: The independent variable is the factor that is intentionally changed by the experimenter. In this investigation, the surface area of magnesium is changed (ribbon in experiment 1 vs. powder in experiment 2).
  • Independent variable: Surface area of magnesium
• 12.2.2 Controlled variable: Controlled variables are factors kept constant to