Kinetics and the Virtual Molecular Dynamics Lab Kinetics Made Easy Susan Grillo Jay Chandler Dan Burton

Introduction This is a traditional kinetic unit which incorporates Simulabs as a supplement. Incorporation of SimuLab will aid the visual interpretation of the kinetics of a reaction.

Intended Audience Advanced Placement or Chem II Students. The topics of kinetics and rate laws are incorporated in the SAT II to a very slight degree, and to a larger degree on the AP Chem Exam. The Simulabs are intended to enhance the students understanding of kinetics.

Placement in the Curriculum The unit will enhance the curriculum already in place. The major revision is the use of the appropriate SimuLabs to enhance the understanding of 1st and 2nd order reactions and activation energy. Students need an understanding of reactions rates prior to starting this unit.

Adjustments / Adaptation Honors 1 Chemistry No Zero Order or fractional reaction rates. Substitute the Methyl Violet Lab with the Vitamin C Clock Lab. Chemistry No Graphing. Only use Vitamin C Clock Lab. Only show the relationship between initial conc., temp., and rate.

Goals and Objectives Students will define the key terms involved in chemical kinetics and factors affecting rate. Students will use lab data and construct graphs to determine reaction order and the rate law. Students will apply the Arrhenius Equation to calculate activation energy and constants. Students will be able to develop a procedure to determine the rate law of a reaction. Given experimental data, students will be able to derive a rate law and select an appropriate mechanism for a reaction.

Time Pre-Lab, Lab and Post-Lab Instructional Five days are required for instruction related to zero, first, and second order reactions and to discuss the differential and integrated rate laws, half-life and slope equation. Two days are needed for a wet lab. Two days are required for Simulabs 2.1; 2.2; 2.3. One day is required for Poster/PowerPoint presentation.

Resources Crystal violet lab: Crystal violet (2.0 x 10 –5 M) NaOH (0.10M) Set-up time is approximately 1 hour.

Demonstrations Surface area demonstration. Elephant’s toothpaste catalysis demonstration: 30% H 2 O 2 ( 125 mL) KI Dishwashing liquid Food coloring

Electronic Equipment CBL/ Spec 20 Notes: If CBL’s used then only one is needed for graphing. Simulab requires one computer for every two to three students. CBL Probes for colorimetry.

Instructional Activities Chronology Day One: Introduction to reaction rates Demonstrations Days Two - Four: Average rate versus instantaneous rate: Method of initial rate Types of rate laws Use of integrated rates Use of zero order, 1 st and 2 nd order rates Graphing of integrated rate laws Half-life

Instructional Activities Chronology Continued Day five: Mechanisms/ rate-determining step/ intermediates Collision model Catalysis Days six – nine: Laboratories: Crystal violet SimuLab # 2.1, 2.2; 2.3 (From the Yellow book) Day ten- eleven: Poster/PowerPoint preparation & presentation

Students will complete the lab and graph: [red] vs time 1/[red] vs time Ln [Red] versus time to determine k, half-life, and order of reaction 2.1 Simulab

Simulab 2.2: Students will complete Simulab 2.2 and will graph: Students will complete the lab and graph: [red] vs time 1/[red] vs time Ln [red] versus time to determine k, half-life, and order of reaction.

Students will: run Simulab 2.3 three times at different temperatures. calculate k for each temperature. use the Arrhenius equation to calculate the activation energy. Simulab 2.3:

Assessment Students must produce a traditional lab report in response to the wet lab. Students will submit problem sets to be graded. A traditional end of unit, criterion- based test will be administered.

Assessment Continued Students will produce a PowerPoint /Posterboard summary of their Simulab work and answer the following questions: 1. How is the rate constant determined graphically? 2. How is the rate order determined graphically? 3. How does the initial concentration affect the half- life? 4. How does the change in temperature affect the rate constant? 5. Using collision theory, explain the difference between first and second order reactions.

Rate Law Summary By integrating Simulabs with wet labs: Students will be exposed to visual representations of the rate laws of various order. Students will make connections between the dynamic molecular models and the graphs and equations which define the various rate laws.

Rate Law Summary Continued Students will explore the relationships between temperature, reaction rates, and constants as well as initial concentration and half-life. Students will be able to calculate the activation energy from their data.