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 ChemistryNo 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-LabInstructional

•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% H2O2 ( 125 mL)KIDishwashing liquidFood 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 ratesDemonstrations

Days Two - Four: Average rate versus instantaneous rate:

Method of initial rateTypes of rate lawsUse of integrated ratesUse of zero order, 1st and 2nd order ratesGraphing of integrated rate lawsHalf-life

Instructional ActivitiesChronology Continued

Day five:Mechanisms/ rate-determining step/ intermediatesCollision modelCatalysis

Days six – nine:Laboratories:Crystal violetSimuLab # 2.1, 2.2; 2.3 (From the Yellow book)

Day ten- eleven:Poster/PowerPoint preparation & presentation

ln [red] vs time

y = -0.0036x + 6.0429

R2 = 0.9987

0

1

2

3

4

5

6

0 200 400 600 800 1000 1200

time

Ln

[re

d]

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.