- Aligned with Big Idea 4 and Learning Objective 4.1
- Emphasizes Science Practices 1, 2, 3, 4, 5, 6, and 7
Investigate factors that affect the rate of a reaction using the iodine clock reaction. Teach this laboratory experience using either the guided activity or inquiry activity. In the guided activity, students measure how quickly clear, colorless solutions of reactants turn deep blue when the temperature, concentration, and surface area of solid reactants are changed. The change in reaction time when a catalyst is added is also determined.
In the inquiry activity, students design an experiment to determine the effect of changing temperature, concentration, surface area of solid reactants, and the presence of a catalyst on the rate of the iodine clock reaction. The inquiry activity provides an opportunity for students to present their experiment design and results, reinforcing the practice of communicating findings. Detailed preparation and procedure notes guide you through leading a successful inquiry exercise, including a suggested rubric for assessing student performance.
Both activities include Big Idea assessment questions that follow the format of the AP® Chemistry Exam free-response questions. In the Big Idea assessment, students draw an energy diagram to show how a catalyst lowers activation energy and predict how changes in concentration and reactant surface area will affect the reaction rate of a single replacement reaction in aqueous solution. Students also predict the effect of increasing pressure on the reaction rate of 2 gases. To answer these questions, students reference physical models, such as the increased number of collisions of molecules with increased temperature.
This kit provides the following AP® Chemistry experiences: design a procedure to collect data, analyze data, explain phenomena based on physical evidence, and make predictions about natural phenomena based on scientific models. The use of the iodine clock reaction gives this experiment visual interest and a precise way to measure reaction rate. Materials are sufficient for 30 students in teams of 3. Digital teacher’s manual, included FREE with kit purchase or sold separately, is a 12-month eBook license to the Factors Affecting Reaction Rates teacher’s manual. You can also access the digital student guide for this kit for free at
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